Add support for signing images using a new signature node. The process is handled by fdt_add_verification_data() which now takes parameters to provide the keys and related information.

Signed-off-by: Simon Glass sjg@chromium.org --- Changes in v3: - Use new fdt_first/next_subnode()

Changes in v2: - Adjust how signing enable works in image.h - Fix FDT error handling in fit_image_write_sig() - Fix checkpatch checks about parenthesis alignment - Fix checkpatch warnings about split strings - Require CONFIG_FIT_SIGNATURE in image.h for mkimage to support signing

common/image-fit.c | 83 +++++++++++++----- common/image-sig.c | 144 +++++++++++++++++++++++++++++++ doc/uImage.FIT/sign-images.its | 42 ++++++++++ include/image.h | 59 ++++++++++++- tools/fit_image.c | 2 +- tools/image-host.c | 186 ++++++++++++++++++++++++++++++++++++++--- 6 files changed, 478 insertions(+), 38 deletions(-) create mode 100644 doc/uImage.FIT/sign-images.its

diff --git a/common/image-fit.c b/common/image-fit.c index 7bf82d3..06426ad 100644 --- a/common/image-fit.c +++ b/common/image-fit.c @@ -234,42 +234,45 @@ void fit_print_contents(const void *fit) * @fit: pointer to the FIT format image header * @noffset: offset of the hash node * @p: pointer to prefix string + * @type: Type of information to print ("hash" or "sign") * * fit_image_print_data() lists properies for the processed hash node * + * This function avoid using puts() since it prints a newline on the host + * but does not in U-Boot. + * * returns: * no returned results */ -static void fit_image_print_data(const void *fit, int noffset, const char *p) +static void fit_image_print_data(const void *fit, int noffset, const char *p, + const char *type) { - char *algo; + const char *keyname; uint8_t *value; int value_len; - int i, ret; - - /* - * Check subnode name, must be equal to "hash". - * Multiple hash nodes require unique unit node - * names, e.g. hash@1, hash@2, etc. - */ - if (strncmp(fit_get_name(fit, noffset, NULL), - FIT_HASH_NODENAME, - strlen(FIT_HASH_NODENAME)) != 0) - return; + char *algo; + int required; + int ret, i;

- debug("%s Hash node: '%s'\n", p, + debug("%s %s node: '%s'\n", p, type, fit_get_name(fit, noffset, NULL)); - - printf("%s Hash algo: ", p); + printf("%s %s algo: ", p, type); if (fit_image_hash_get_algo(fit, noffset, &algo)) { printf("invalid/unsupported\n"); return; } - printf("%s\n", algo); + printf("%s", algo); + keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL); + required = fdt_getprop(fit, noffset, "required", NULL) != NULL; + if (keyname) + printf(":%s", keyname); + if (required) + printf(" (required)"); + printf("\n");

ret = fit_image_hash_get_value(fit, noffset, &value, &value_len); - printf("%s Hash value: ", p); + printf("%s %s value: ", p, type); if (ret) { printf("unavailable\n"); } else { @@ -278,7 +281,18 @@ static void fit_image_print_data(const void *fit, int noffset, const char *p) printf("\n"); }

- debug("%s Hash len: %d\n", p, value_len); + debug("%s %s len: %d\n", p, type, value_len); + + /* Signatures have a time stamp */ + if (IMAGE_ENABLE_TIMESTAMP && keyname) { + time_t timestamp; + + printf("%s Timestamp: ", p); + if (fit_get_timestamp(fit, noffset, &timestamp)) + printf("unavailable\n"); + else + genimg_print_time(timestamp); + } }

/** @@ -303,8 +317,12 @@ static void fit_image_print_verification_data(const void *fit, int noffset, * names, e.g. hash@1, hash@2, signature@1, signature@2, etc. */ name = fit_get_name(fit, noffset, NULL); - if (!strncmp(name, FIT_HASH_NODENAME, strlen(FIT_HASH_NODENAME))) - fit_image_print_data(fit, noffset, p); + if (!strncmp(name, FIT_HASH_NODENAME, strlen(FIT_HASH_NODENAME))) { + fit_image_print_data(fit, noffset, p, "Hash"); + } else if (!strncmp(name, FIT_SIG_NODENAME, + strlen(FIT_SIG_NODENAME))) { + fit_image_print_data(fit, noffset, p, "Sign"); + } }

/** @@ -944,13 +962,23 @@ int fit_image_verify(const void *fit, int image_noffset) { const void *data; size_t size; - int noffset; + int noffset = 0; char *err_msg = ""; + int verify_all = 1; + int ret;

/* Get image data and data length */ if (fit_image_get_data(fit, image_noffset, &data, &size)) { err_msg = "Can't get image data/size"; - return 0; + goto error; + } + + /* Verify all required signatures */ + if (IMAGE_ENABLE_VERIFY && + fit_image_verify_required_sigs(fit, image_noffset, data, size, + gd_fdt_blob(), &verify_all)) { + err_msg = "Unable to verify required signature"; + goto error; }

/* Process all hash subnodes of the component image node */ @@ -970,6 +998,15 @@ int fit_image_verify(const void *fit, int image_noffset) &err_msg)) goto error; puts("+ "); + } else if (IMAGE_ENABLE_VERIFY && verify_all && + !strncmp(name, FIT_SIG_NODENAME, + strlen(FIT_SIG_NODENAME))) { + ret = fit_image_check_sig(fit, noffset, data, + size, -1, &err_msg); + if (ret) + puts("- "); + else + puts("+ "); } }

diff --git a/common/image-sig.c b/common/image-sig.c index 841c662..9b222da 100644 --- a/common/image-sig.c +++ b/common/image-sig.c @@ -22,6 +22,8 @@ #include <time.h> #else #include <common.h> +#include <malloc.h> +DECLARE_GLOBAL_DATA_PTR; #endif /* !USE_HOSTCC*/ #include <errno.h> #include <image.h> @@ -40,3 +42,145 @@ struct image_sig_algo *image_get_sig_algo(const char *name)

return NULL; } + +static int fit_image_setup_verify(struct image_sign_info *info, + const void *fit, int noffset, int required_keynode, + char **err_msgp) +{ + char *algo_name; + + if (fit_image_hash_get_algo(fit, noffset, &algo_name)) { + *err_msgp = "Can't get hash algo property"; + return -1; + } + memset(info, '\0', sizeof(*info)); + info->keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL); + info->fit = (void *)fit; + info->node_offset = noffset; + info->algo = image_get_sig_algo(algo_name); + info->fdt_blob = gd_fdt_blob(); + info->required_keynode = required_keynode; + printf("%s:%s", algo_name, info->keyname); + + if (!info->algo) { + *err_msgp = "Unknown signature algorithm"; + return -1; + } + + return 0; +} + +int fit_image_check_sig(const void *fit, int noffset, const void *data, + size_t size, int required_keynode, char **err_msgp) +{ + struct image_sign_info info; + struct image_region region; + uint8_t *fit_value; + int fit_value_len; + + *err_msgp = NULL; + if (fit_image_setup_verify(&info, fit, noffset, required_keynode, + err_msgp)) + return -1; + + if (fit_image_hash_get_value(fit, noffset, &fit_value, + &fit_value_len)) { + *err_msgp = "Can't get hash value property"; + return -1; + } + + region.data = data; + region.size = size; + + if (info.algo->verify(&info, &region, 1, fit_value, fit_value_len)) { + *err_msgp = "Verification failed"; + return -1; + } + + return 0; +} + +static int fit_image_verify_sig(const void *fit, int image_noffset, + const char *data, size_t size, const void *sig_blob, + int sig_offset) +{ + int noffset; + char *err_msg = ""; + int verified = 0; + int ret; + + /* Process all hash subnodes of the component image node */ + for (noffset = fdt_first_subnode(fit, image_noffset); + noffset >= 0; + noffset = fdt_next_subnode(fit, noffset)) { + const char *name = fit_get_name(fit, noffset, NULL); + + if (!strncmp(name, FIT_SIG_NODENAME, + strlen(FIT_SIG_NODENAME))) { + ret = fit_image_check_sig(fit, noffset, data, + size, -1, &err_msg); + if (ret) { + puts("- "); + } else { + puts("+ "); + verified = 1; + break; + } + } + } + + if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) { + err_msg = "Corrupted or truncated tree"; + goto error; + } + + return verified ? 0 : -EPERM; + +error: + printf(" error!\n%s for '%s' hash node in '%s' image node\n", + err_msg, fit_get_name(fit, noffset, NULL), + fit_get_name(fit, image_noffset, NULL)); + return -1; +} + +int fit_image_verify_required_sigs(const void *fit, int image_noffset, + const char *data, size_t size, const void *sig_blob, + int *no_sigsp) +{ + int verify_count = 0; + int noffset; + int sig_node; + + /* Work out what we need to verify */ + *no_sigsp = 1; + sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME); + if (sig_node < 0) { + debug("%s: No signature node found: %s\n", __func__, + fdt_strerror(sig_node)); + return 0; + } + + for (noffset = fdt_first_subnode(sig_blob, sig_node); + noffset >= 0; + noffset = fdt_next_subnode(sig_blob, noffset)) { + const char *required; + int ret; + + required = fdt_getprop(sig_blob, noffset, "required", NULL); + if (!required || strcmp(required, "image")) + continue; + ret = fit_image_verify_sig(fit, image_noffset, data, size, + sig_blob, noffset); + if (ret) { + printf("Failed to verify required signature '%s'\n", + fit_get_name(sig_blob, noffset, NULL)); + return ret; + } + verify_count++; + } + + if (verify_count) + *no_sigsp = 0; + + return 0; +} diff --git a/doc/uImage.FIT/sign-images.its b/doc/uImage.FIT/sign-images.its new file mode 100644 index 0000000..f69326a --- /dev/null +++ b/doc/uImage.FIT/sign-images.its @@ -0,0 +1,42 @@ +/dts-v1/; + +/ { + description = "Chrome OS kernel image with one or more FDT blobs"; + #address-cells = <1>; + + images { + kernel@1 { + data = /incbin/("test-kernel.bin"); + type = "kernel_noload"; + arch = "sandbox"; + os = "linux"; + compression = "none"; + load = <0x4>; + entry = <0x8>; + kernel-version = <1>; + signature@1 { + algo = "sha1,rsa2048"; + key-name-hint = "dev"; + }; + }; + fdt@1 { + description = "snow"; + data = /incbin/("sandbox-kernel.dtb"); + type = "flat_dt"; + arch = "sandbox"; + compression = "none"; + fdt-version = <1>; + signature@1 { + algo = "sha1,rsa2048"; + key-name-hint = "dev"; + }; + }; + }; + configurations { + default = "conf@1"; + conf@1 { + kernel = "kernel@1"; + fdt = "fdt@1"; + }; + }; +}; diff --git a/include/image.h b/include/image.h index 3f61682..da7b9a0 100644 --- a/include/image.h +++ b/include/image.h @@ -766,12 +766,26 @@ int fit_image_hash_get_value(const void *fit, int noffset, uint8_t **value, int fit_set_timestamp(void *fit, int noffset, time_t timestamp);

/** - * fit_add_verification_data() - Calculate and add hashes to FIT + * fit_add_verification_data() - add verification data to FIT image nodes * - * @fit: Fit image to process - * @return 0 if ok, <0 for error + * @keydir: Directory containing keys + * @kwydest: FDT blob to write public key information to + * @fit: Pointer to the FIT format image header + * @comment: Comment to add to signature nodes + * @require_keys: Mark all keys as 'required' + * + * Adds hash values for all component images in the FIT blob. + * Hashes are calculated for all component images which have hash subnodes + * with algorithm property set to one of the supported hash algorithms. + * + * Also add signatures if signature nodes are present. + * + * returns + * 0, on success + * libfdt error code, on failure */ -int fit_add_verification_data(void *fit); +int fit_add_verification_data(const char *keydir, void *keydest, void *fit, + const char *comment, int require_keys);

int fit_image_verify(const void *fit, int noffset); int fit_config_verify(const void *fit, int conf_noffset); @@ -914,6 +928,43 @@ struct image_sig_algo { */ struct image_sig_algo *image_get_sig_algo(const char *name);

+/** + * fit_image_verify_required_sigs() - Verify signatures marked as 'required' + * + * @fit: FIT to check + * @image_noffset: Offset of image node to check + * @data: Image data to check + * @size: Size of image data + * @sig_blob: FDT containing public keys + * @no_sigsp: Returns 1 if no signatures were required, and + * therefore nothing was checked. The caller may wish + * to fall back to other mechanisms, or refuse to + * boot. + * @return 0 if all verified ok, <0 on error + */ +int fit_image_verify_required_sigs(const void *fit, int image_noffset, + const char *data, size_t size, const void *sig_blob, + int *no_sigsp); + +/** + * fit_image_check_sig() - Check a single image signature node + * + * @fit: FIT to check + * @noffset: Offset of signature node to check + * @data: Image data to check + * @size: Size of image data + * @required_keynode: Offset in the control FDT of the required key node, + * if any. If this is given, then the image wil not + * pass verification unless that key is used. If this is + * -1 then any signature will do. + * @err_msgp: In the event of an error, this will be pointed to a + * help error string to display to the user. + * @return 0 if all verified ok, <0 on error + */ +int fit_image_check_sig(const void *fit, int noffset, const void *data, + size_t size, int required_keynode, char **err_msgp); + + static inline int fit_image_check_target_arch(const void *fdt, int node) { return fit_image_check_arch(fdt, node, IH_ARCH_DEFAULT); diff --git a/tools/fit_image.c b/tools/fit_image.c index cc123dd..ef6ef44 100644 --- a/tools/fit_image.c +++ b/tools/fit_image.c @@ -137,7 +137,7 @@ static int fit_handle_file (struct mkimage_params *params) goto err_mmap;

/* set hashes for images in the blob */ - if (fit_add_verification_data(ptr)) { + if (fit_add_verification_data(NULL, NULL, ptr, NULL, 0)) { fprintf (stderr, "%s Can't add hashes to FIT blob", params->cmdname); goto err_add_hashes; diff --git a/tools/image-host.c b/tools/image-host.c index d944d0f..7aebc29 100644 --- a/tools/image-host.c +++ b/tools/image-host.c @@ -26,12 +26,8 @@ */

#include "mkimage.h" -#include <bootstage.h> #include <image.h> -#include <sha1.h> -#include <time.h> -#include <u-boot/crc.h> -#include <u-boot/md5.h> +#include <version.h>

/** * fit_set_hash_value - set hash value in requested has node @@ -108,9 +104,165 @@ static int fit_image_process_hash(void *fit, const char *image_name, }

/** - * fit_image_add_verification_data() - calculate/set hash data for image node + * fit_image_write_sig() - write the signature to a FIT * - * This adds hash values for a component image node. + * This writes the signature and signer data to the FIT. + * + * @fit: pointer to the FIT format image header + * @noffset: hash node offset + * @value: signature value to be set + * @value_len: signature value length + * @comment: Text comment to write (NULL for none) + * + * returns + * 0, on success + * -FDT_ERR_..., on failure + */ +static int fit_image_write_sig(void *fit, int noffset, uint8_t *value, + int value_len, const char *comment, const char *region_prop, + int region_proplen) +{ + int string_size; + int ret; + + /* + * Get the current string size, before we update the FIT and add + * more + */ + string_size = fdt_size_dt_strings(fit); + + ret = fdt_setprop(fit, noffset, FIT_VALUE_PROP, value, value_len); + if (!ret) { + ret = fdt_setprop_string(fit, noffset, "signer-name", + "mkimage"); + } + if (!ret) { + ret = fdt_setprop_string(fit, noffset, "signer-version", + PLAIN_VERSION); + } + if (comment && !ret) + ret = fdt_setprop_string(fit, noffset, "comment", comment); + if (!ret) + ret = fit_set_timestamp(fit, noffset, time(NULL)); + if (region_prop && !ret) { + uint32_t strdata[2]; + + ret = fdt_setprop(fit, noffset, "hashed-nodes", + region_prop, region_proplen); + strdata[0] = 0; + strdata[1] = cpu_to_fdt32(string_size); + if (!ret) { + ret = fdt_setprop(fit, noffset, "hashed-strings", + strdata, sizeof(strdata)); + } + } + + return ret; +} + +static int fit_image_setup_sig(struct image_sign_info *info, + const char *keydir, void *fit, const char *image_name, + int noffset, const char *require_keys) +{ + const char *node_name; + char *algo_name; + + node_name = fit_get_name(fit, noffset, NULL); + if (fit_image_hash_get_algo(fit, noffset, &algo_name)) { + printf("Can't get algo property for '%s' signature node in '%s' image node\n", + node_name, image_name); + return -1; + } + + memset(info, '\0', sizeof(*info)); + info->keydir = keydir; + info->keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL); + info->fit = fit; + info->node_offset = noffset; + info->algo = image_get_sig_algo(algo_name); + info->require_keys = require_keys; + if (!info->algo) { + printf("Unsupported signature algorithm (%s) for '%s' signature node in '%s' image node\n", + algo_name, node_name, image_name); + return -1; + } + + return 0; +} + +/** + * fit_image_process_sig- Process a single subnode of the images/ node + * + * Check each subnode and process accordingly. For signature nodes we + * generate a signed hash of the supplised data and store it in the node. + * + * @keydir: Directory containing keys to use for signing + * @keydest: Destination FDT blob to write public keys into + * @fit: pointer to the FIT format image header + * @image_name: name of image being processes (used to display errors) + * @noffset: subnode offset + * @data: data to process + * @size: size of data in bytes + * @comment: Comment to add to signature nodes + * @require_keys: Mark all keys as 'required' + * @return 0 if ok, -1 on error + */ +static int fit_image_process_sig(const char *keydir, void *keydest, + void *fit, const char *image_name, + int noffset, const void *data, size_t size, + const char *comment, int require_keys) +{ + struct image_sign_info info; + struct image_region region; + const char *node_name; + uint8_t *value; + uint value_len; + int ret; + + if (fit_image_setup_sig(&info, keydir, fit, image_name, noffset, + require_keys ? "image" : NULL)) + return -1; + + node_name = fit_get_name(fit, noffset, NULL); + region.data = data; + region.size = size; + ret = info.algo->sign(&info, &region, 1, &value, &value_len); + if (ret) { + printf("Failed to sign '%s' signature node in '%s' image node: %d\n", + node_name, image_name, ret); + + /* We allow keys to be missing */ + if (ret == -ENOENT) + return 0; + return -1; + } + + ret = fit_image_write_sig(fit, noffset, value, value_len, comment, + NULL, 0); + if (ret) { + printf("Can't write signature for '%s' signature node in '%s' image node: %s\n", + node_name, image_name, fdt_strerror(ret)); + return -1; + } + free(value); + + /* Get keyname again, as FDT has changed and invalidated our pointer */ + info.keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL); + + /* Write the public key into the supplied FDT file */ + if (keydest && info.algo->add_verify_data(&info, keydest)) { + printf("Failed to add verification data for '%s' signature node in '%s' image node\n", + node_name, image_name); + return -1; + } + + return 0; +} + +/** + * fit_image_add_verification_data() - calculate/set verig. data for image node + * + * This adds hash and signature values for an component image node. * * All existing hash subnodes are checked, if algorithm property is set to * one of the supported hash algorithms, hash value is computed and @@ -133,11 +285,17 @@ static int fit_image_process_hash(void *fit, const char *image_name, * * For signature details, please see doc/uImage.FIT/signature.txt * + * @keydir Directory containing *.key and *.crt files (or NULL) + * @keydest FDT Blob to write public keys into (NULL if none) * @fit: Pointer to the FIT format image header * @image_noffset: Requested component image node + * @comment: Comment to add to signature nodes + * @require_keys: Mark all keys as 'required' * @return: 0 on success, <0 on failure */ -int fit_image_add_verification_data(void *fit, int image_noffset) +int fit_image_add_verification_data(const char *keydir, void *keydest, + void *fit, int image_noffset, const char *comment, + int require_keys) { const char *image_name; const void *data; @@ -169,6 +327,12 @@ int fit_image_add_verification_data(void *fit, int image_noffset) strlen(FIT_HASH_NODENAME))) { ret = fit_image_process_hash(fit, image_name, noffset, data, size); + } else if (IMAGE_ENABLE_SIGN && keydir && + !strncmp(node_name, FIT_SIG_NODENAME, + strlen(FIT_SIG_NODENAME))) { + ret = fit_image_process_sig(keydir, keydest, + fit, image_name, noffset, data, size, + comment, require_keys); } if (ret) return -1; @@ -177,7 +341,8 @@ int fit_image_add_verification_data(void *fit, int image_noffset) return 0; }

-int fit_add_verification_data(void *fit) +int fit_add_verification_data(const char *keydir, void *keydest, void *fit, + const char *comment, int require_keys) { int images_noffset; int noffset; @@ -199,7 +364,8 @@ int fit_add_verification_data(void *fit) * Direct child node of the images parent node, * i.e. component image node. */ - ret = fit_image_add_verification_data(fit, noffset); + ret = fit_image_add_verification_data(keydir, keydest, + fit, noffset, comment, require_keys); if (ret) return ret; }

Keys required for signing images will be in a specific directory. Add a -k option to specify that directory.

Also update the mkimage man page with this information and a clearer list of available commands.

Signed-off-by: Simon Glass sjg@chromium.org Reviewed-by: Marek Vasut marex@denx.de (v1) --- Changes in v3: None Changes in v2: - Adjust mkimage help to separate out signing options - Fix checkpatch warnings about split strings

doc/mkimage.1 | 25 ++++++++++++++++++++++--- tools/fit_image.c | 2 +- tools/mkimage.c | 15 ++++++++++++++- tools/mkimage.h | 1 + 4 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/doc/mkimage.1 b/doc/mkimage.1 index 39652c8..6740fb1 100644 --- a/doc/mkimage.1 +++ b/doc/mkimage.1 @@ -4,7 +4,14 @@ mkimage - Generate image for U-Boot .SH SYNOPSIS .B mkimage -.RB [\fIoptions\fP] +.RB "-l [" "uimage file name" "]" + +.B mkimage +.RB [\fIoptions\fP] " -f [" "image tree source file" "]" " [" "uimage file name" "]" + +.B mkimage +.RB [\fIoptions\fP] " (legacy mode)" + .SH "DESCRIPTION" The .B mkimage @@ -26,7 +33,8 @@ etc. The new .I FIT (Flattened Image Tree) format allows for more flexibility in handling images of various types and also -enhances integrity protection of images with stronger checksums. +enhances integrity protection of images with stronger checksums. It also +supports verified boot.

.SH "OPTIONS"

@@ -67,6 +75,10 @@ Set load address with a hex number. Set entry point with a hex number.

.TP +.BI "-l" +List the contents of an image. + +.TP .BI "-n [" "image name" "]" Set image name to 'image name'.

@@ -91,6 +103,12 @@ create the image. Image tree source file that describes the structure and contents of the FIT image.

+.TP +.BI "-k [" "key_directory" "]" +Specifies the directory containing keys to use for signing. This directory +should contain a private key file <name>.key for use with signing and a +certificate <name>.crt (containing the public key) for use with verification. + .SH EXAMPLES

List image information: @@ -115,4 +133,5 @@ http://www.denx.de/wiki/U-Boot/WebHome .PP .SH AUTHOR This manual page was written by Nobuhiro Iwamatsu iwamatsu@nigauri.org -and Wolfgang Denk wd@denx.de +and Wolfgang Denk wd@denx.de. It was updated for image signing by +Simon Glass sjg@chromium.org. diff --git a/tools/fit_image.c b/tools/fit_image.c index ef6ef44..339e0f8 100644 --- a/tools/fit_image.c +++ b/tools/fit_image.c @@ -137,7 +137,7 @@ static int fit_handle_file (struct mkimage_params *params) goto err_mmap;

/* set hashes for images in the blob */ - if (fit_add_verification_data(NULL, NULL, ptr, NULL, 0)) { + if (fit_add_verification_data(params->keydir, NULL, ptr, NULL, 0)) { fprintf (stderr, "%s Can't add hashes to FIT blob", params->cmdname); goto err_add_hashes; diff --git a/tools/mkimage.c b/tools/mkimage.c index e43b09f..def7df2 100644 --- a/tools/mkimage.c +++ b/tools/mkimage.c @@ -248,6 +248,11 @@ main (int argc, char **argv) params.datafile = *++argv; params.fflag = 1; goto NXTARG; + case 'k': + if (--argc <= 0) + usage(); + params.keydir = *++argv; + goto NXTARG; case 'n': if (--argc <= 0) usage (); @@ -623,8 +628,16 @@ usage () " -d ==> use image data from 'datafile'\n" " -x ==> set XIP (execute in place)\n", params.cmdname); - fprintf (stderr, " %s [-D dtc_options] -f fit-image.its fit-image\n", + fprintf(stderr, " %s [-D dtc_options] -f fit-image.its fit-image\n", params.cmdname); + fprintf(stderr, " -D => set options for device tree compiler\n" + " -f => input filename for FIT source\n"); +#ifdef CONFIG_FIT_SIGNATURE + fprintf(stderr, "Signing / verified boot options: [-k keydir]\n" + " -k => set directory containing private keys\n"); +#else + fprintf(stderr, "Signing / verified boot not supported (CONFIG_FIT_SIGNATURE undefined)\n"); +#endif fprintf (stderr, " %s -V ==> print version information and exit\n", params.cmdname);

diff --git a/tools/mkimage.h b/tools/mkimage.h index 03c6c8f..059e124 100644 --- a/tools/mkimage.h +++ b/tools/mkimage.h @@ -87,6 +87,7 @@ struct mkimage_params { char *datafile; char *imagefile; char *cmdname; + const char *keydir; /* Directory holding private keys */ };

/*

When signing images it is sometimes necessary to sign with different keys at different times, or make the signer entirely separate from the FIT creation to avoid needing the private keys to be publicly available in the system.

Add a -F option so that key signing can be a separate step, and possibly done multiple times as different keys are avaiable.

Signed-off-by: Simon Glass sjg@chromium.org Reviewed-by: Marek Vasut marex@denx.de --- Changes in v3: None Changes in v2: - Adjust mkimage help to separate out signing options - Fix checkpatch checks about parenthesis alignment - Rebase on previous patches

doc/mkimage.1 | 20 ++++++++++++++++++++ tools/fit_image.c | 18 ++++++++++++------ tools/mkimage.c | 9 ++++++--- 3 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/doc/mkimage.1 b/doc/mkimage.1 index 8185ff5..f9c733a 100644 --- a/doc/mkimage.1 +++ b/doc/mkimage.1 @@ -10,6 +10,9 @@ mkimage - Generate image for U-Boot .RB [\fIoptions\fP] " -f [" "image tree source file" "]" " [" "uimage file name" "]"

.B mkimage +.RB [\fIoptions\fP] " -F [" "uimage file name" "]" + +.B mkimage .RB [\fIoptions\fP] " (legacy mode)"

.SH "DESCRIPTION" @@ -104,6 +107,13 @@ Image tree source file that describes the structure and contents of the FIT image.

.TP +.BI "-F" +Indicates that an existing FIT image should be modified. No dtc +compilation is performed and the -f flag should not be given. +This can be used to sign images with additional keys after initial image +creation. + +.TP .BI "-k [" "key_directory" "]" Specifies the directory containing keys to use for signing. This directory should contain a private key file <name>.key for use with signing and a @@ -144,6 +154,16 @@ skipping those for which keys cannot be found. Also add a comment. -c "Kernel 3.8 image for production devices" kernel.itb .fi

+.P +Update an existing FIT image, signing it with additional keys. +Add corresponding public keys into u-boot.dtb. This will resign all images +with keys that are available in the new directory. Images that request signing +with unavailable keys are skipped. +.nf +.B mkimage -F -k /secret/signing-keys -K u-boot.dtb \\ +-c "Kernel 3.8 image for production devices" kernel.itb +.fi + .SH HOMEPAGE http://www.denx.de/wiki/U-Boot/WebHome .PP diff --git a/tools/fit_image.c b/tools/fit_image.c index b17fa2d..645e93c 100644 --- a/tools/fit_image.c +++ b/tools/fit_image.c @@ -124,10 +124,16 @@ static int fit_handle_file (struct mkimage_params *params) } sprintf (tmpfile, "%s%s", params->imagefile, MKIMAGE_TMPFILE_SUFFIX);

- /* dtc -I dts -O dtb -p 500 datafile > tmpfile */ - sprintf (cmd, "%s %s %s > %s", - MKIMAGE_DTC, params->dtc, params->datafile, tmpfile); - debug ("Trying to execute "%s"\n", cmd); + /* We either compile the source file, or use the existing FIT image */ + if (params->datafile) { + /* dtc -I dts -O dtb -p 500 datafile > tmpfile */ + snprintf(cmd, sizeof(cmd), "%s %s %s > %s", + MKIMAGE_DTC, params->dtc, params->datafile, tmpfile); + debug("Trying to execute "%s"\n", cmd); + } else { + snprintf(cmd, sizeof(cmd), "cp %s %s", + params->imagefile, tmpfile); + } if (system (cmd) == -1) { fprintf (stderr, "%s: system(%s) failed: %s\n", params->cmdname, cmd, strerror(errno)); @@ -153,8 +159,8 @@ static int fit_handle_file (struct mkimage_params *params) goto err_add_hashes; }

- /* add a timestamp at offset 0 i.e., root */ - if (fit_set_timestamp (ptr, 0, sbuf.st_mtime)) { + /* for first image creation, add a timestamp at offset 0 i.e., root */ + if (params->datafile && fit_set_timestamp(ptr, 0, sbuf.st_mtime)) { fprintf (stderr, "%s: Can't add image timestamp\n", params->cmdname); goto err_add_timestamp; diff --git a/tools/mkimage.c b/tools/mkimage.c index 3760392..e2b82d0 100644 --- a/tools/mkimage.c +++ b/tools/mkimage.c @@ -240,12 +240,14 @@ main (int argc, char **argv) case 'f': if (--argc <= 0) usage (); + params.datafile = *++argv; + /* no break */ + case 'F': /* * The flattened image tree (FIT) format * requires a flattened device tree image type */ params.type = IH_TYPE_FLATDT; - params.datafile = *++argv; params.fflag = 1; goto NXTARG; case 'k': @@ -633,14 +635,15 @@ usage () " -d ==> use image data from 'datafile'\n" " -x ==> set XIP (execute in place)\n", params.cmdname); - fprintf(stderr, " %s [-D dtc_options] -f fit-image.its fit-image\n", + fprintf(stderr, " %s [-D dtc_options] [-f fit-image.its|-F] fit-image\n", params.cmdname); fprintf(stderr, " -D => set options for device tree compiler\n" " -f => input filename for FIT source\n"); #ifdef CONFIG_FIT_SIGNATURE fprintf(stderr, "Signing / verified boot options: [-k keydir] [-K dtb]\n" " -k => set directory containing private keys\n" - " -K => write public keys to this .dtb file\n"); + " -K => write public keys to this .dtb file\n" + " -F => re-sign existing FIT image\n"); #else fprintf(stderr, "Signing / verified boot not supported (CONFIG_FIT_SIGNATURE undefined)\n"); #endif

Normally, multiple public keys can be provided and U-Boot is not required to use all of them for verification. This is because some images may not be signed, or may be optionally signed.

But we still need a mechanism to determine when a key must be used. This feature cannot be implemented in the FIT itself, since anyone could change it to mark a key as optional. The requirement for key verification must go in with the public keys, in a place that is protected from modification.

Add a -r option which tells mkimage to mark all keys that it uses for signing as 'required'.

If some keys are optional and some are required, run mkimage several times (perhaps with different key directories if some keys are very secret) using the -F flag to update an existing FIT.

Signed-off-by: Simon Glass sjg@chromium.org Reviewed-by: Marek Vasut marex@denx.de --- Changes in v3: None Changes in v2: - Adjust mkimage help to separate out signing options - Rebase on previous patches

doc/mkimage.1 | 6 ++++++ tools/fit_image.c | 9 +++++---- tools/mkimage.c | 8 ++++++-- tools/mkimage.h | 1 + 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/doc/mkimage.1 b/doc/mkimage.1 index b67a351..14374da 100644 --- a/doc/mkimage.1 +++ b/doc/mkimage.1 @@ -133,6 +133,12 @@ the corresponding public key is written into this file for for run-time verification. Typically the file here is the device tree binary used by CONFIG_OF_CONTROL in U-Boot.

+.TP +.BI "-r +Specifies that keys used to sign the FIT are required. This means that they +must be verified for the image to boot. Without this option, the verification +will be optional (useful for testing but not for release). + .SH EXAMPLES

List image information: diff --git a/tools/fit_image.c b/tools/fit_image.c index d48f571..281c2bd 100644 --- a/tools/fit_image.c +++ b/tools/fit_image.c @@ -152,10 +152,11 @@ static int fit_handle_file (struct mkimage_params *params) goto err_mmap;

/* set hashes for images in the blob */ - if (fit_add_verification_data(params->keydir, dest_blob, ptr, - params->comment, 0)) { - fprintf (stderr, "%s Can't add hashes to FIT blob", - params->cmdname); + if (fit_add_verification_data(params->keydir, + dest_blob, ptr, params->comment, + params->require_keys)) { + fprintf(stderr, "%s Can't add hashes to FIT blob\n", + params->cmdname); goto err_add_hashes; }

diff --git a/tools/mkimage.c b/tools/mkimage.c index b3b45a4..d312844 100644 --- a/tools/mkimage.c +++ b/tools/mkimage.c @@ -270,6 +270,9 @@ main (int argc, char **argv) usage (); params.imagename = *++argv; goto NXTARG; + case 'r': + params.require_keys = 1; + break; case 'R': if (--argc <= 0) usage(); @@ -645,11 +648,12 @@ usage () fprintf(stderr, " -D => set options for device tree compiler\n" " -f => input filename for FIT source\n"); #ifdef CONFIG_FIT_SIGNATURE - fprintf(stderr, "Signing / verified boot options: [-k keydir] [-K dtb] [ -c <comment>]\n" + fprintf(stderr, "Signing / verified boot options: [-k keydir] [-K dtb] [ -c <comment>] [-r]\n" " -k => set directory containing private keys\n" " -K => write public keys to this .dtb file\n" " -c => add comment in signature node\n" - " -F => re-sign existing FIT image\n"); + " -F => re-sign existing FIT image\n" + " -r => mark keys used as 'required' in dtb\n"); #else fprintf(stderr, "Signing / verified boot not supported (CONFIG_FIT_SIGNATURE undefined)\n"); #endif diff --git a/tools/mkimage.h b/tools/mkimage.h index ab8baf8..1d9984e 100644 --- a/tools/mkimage.h +++ b/tools/mkimage.h @@ -90,6 +90,7 @@ struct mkimage_params { const char *keydir; /* Directory holding private keys */ const char *keydest; /* Destination .dtb for public key */ const char *comment; /* Comment to add to signature node */ + int require_keys; /* 1 to mark signing keys as 'required' */ };

/*

While signing images is useful, it does not provide complete protection against several types of attack. For example, it it possible to create a FIT with the same signed images, but with the configuration changed such that a different one is selected (mix and match attack). It is also possible to substitute a signed image from an older FIT version into a newer FIT (roll-back attack).

Add support for signing of FIT configurations using the libfdt's region support.

Please see doc/uImage.FIT/signature.txt for more information.

Signed-off-by: Simon Glass sjg@chromium.org --- Changes in v3: - Use new fdt_first/next_subnode()

Changes in v2: - Fix checkpatch checks about parenthesis alignment - Fix checkpatch warnings about split strings - Require CONFIG_FIT_SIGNATURE in image.h for mkimage to support signing - Update README to fix typos and clarify some points - Use stack instead of calloc() within U-Boot's signature verification code

common/image-sig.c | 231 ++++++++++++++++++++++++++- doc/uImage.FIT/sign-configs.its | 45 ++++++ doc/uImage.FIT/signature.txt | 168 +++++++++++++++++++- include/image.h | 16 ++ tools/image-host.c | 341 +++++++++++++++++++++++++++++++++++++++- 5 files changed, 798 insertions(+), 3 deletions(-) create mode 100644 doc/uImage.FIT/sign-configs.its

diff --git a/common/image-sig.c b/common/image-sig.c index 9928bfc..5d907cf 100644 --- a/common/image-sig.c +++ b/common/image-sig.c @@ -25,10 +25,11 @@ #include <malloc.h> DECLARE_GLOBAL_DATA_PTR; #endif /* !USE_HOSTCC*/ -#include <errno.h> #include <image.h> #include <rsa.h>

+#define IMAGE_MAX_HASHED_NODES 100 + struct image_sig_algo image_sig_algos[] = { { "sha1,rsa2048", @@ -50,6 +51,50 @@ struct image_sig_algo *image_get_sig_algo(const char *name) return NULL; }

+/** + * fit_region_make_list() - Make a list of image regions + * + * Given a list of fdt_regions, create a list of image_regions. This is a + * simple conversion routine since the FDT and image code use different + * structures. + * + * @fit: FIT image + * @fdt_regions: Pointer to FDT regions + * @count: Number of FDT regions + * @region: Pointer to image regions, which must hold @count records. If + * region is NULL, then (except for an SPL build) the array will be + * allocated. + * @return: Pointer to image regions + */ +struct image_region *fit_region_make_list(const void *fit, + struct fdt_region *fdt_regions, int count, + struct image_region *region) +{ + int i; + + debug("Hash regions:\n"); + debug("%10s %10s\n", "Offset", "Size"); + + /* + * Use malloc() except in SPL (to save code size). In SPL the caller + * must allocate the array. + */ +#ifndef CONFIG_SPL_BUILD + if (!region) + region = calloc(sizeof(*region), count); +#endif + if (!region) + return NULL; + for (i = 0; i < count; i++) { + debug("%10x %10x\n", fdt_regions[i].offset, + fdt_regions[i].size); + region[i].data = fit + fdt_regions[i].offset; + region[i].size = fdt_regions[i].size; + } + + return region; +} + static int fit_image_setup_verify(struct image_sign_info *info, const void *fit, int noffset, int required_keynode, char **err_msgp) @@ -191,3 +236,187 @@ int fit_image_verify_required_sigs(const void *fit, int image_noffset,

return 0; } + +int fit_config_check_sig(const void *fit, int noffset, int required_keynode, + char **err_msgp) +{ + char * const exc_prop[] = {"data"}; + const char *prop, *end, *name; + struct image_sign_info info; + const uint32_t *strings; + uint8_t *fit_value; + int fit_value_len; + int max_regions; + int i, prop_len; + char path[200]; + int count; + + debug("%s: fdt=%p, conf='%s', sig='%s'\n", __func__, gd_fdt_blob(), + fit_get_name(fit, noffset, NULL), + fit_get_name(gd_fdt_blob(), required_keynode, NULL)); + *err_msgp = NULL; + if (fit_image_setup_verify(&info, fit, noffset, required_keynode, + err_msgp)) + return -1; + + if (fit_image_hash_get_value(fit, noffset, &fit_value, + &fit_value_len)) { + *err_msgp = "Can't get hash value property"; + return -1; + } + + /* Count the number of strings in the property */ + prop = fdt_getprop(fit, noffset, "hashed-nodes", &prop_len); + end = prop ? prop + prop_len : prop; + for (name = prop, count = 0; name < end; name++) + if (!*name) + count++; + if (!count) { + *err_msgp = "Can't get hashed-nodes property"; + return -1; + } + + /* Add a sanity check here since we are using the stack */ + if (count > IMAGE_MAX_HASHED_NODES) { + *err_msgp = "Number of hashed nodes exceeds maximum"; + return -1; + } + + /* Create a list of node names from those strings */ + char *node_inc[count]; + + debug("Hash nodes (%d):\n", count); + for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) { + debug(" '%s'\n", name); + node_inc[i] = (char *)name; + } + + /* + * Each node can generate one region for each sub-node. Allow for + * 7 sub-nodes (hash@1, signature@1, etc.) and some extra. + */ + max_regions = 20 + count * 7; + struct fdt_region fdt_regions[max_regions]; + + /* Get a list of regions to hash */ + count = fdt_find_regions(fit, node_inc, count, + exc_prop, ARRAY_SIZE(exc_prop), + fdt_regions, max_regions - 1, + path, sizeof(path), 0); + if (count < 0) { + *err_msgp = "Failed to hash configuration"; + return -1; + } + if (count == 0) { + *err_msgp = "No data to hash"; + return -1; + } + if (count >= max_regions - 1) { + *err_msgp = "Too many hash regions"; + return -1; + } + + /* Add the strings */ + strings = fdt_getprop(fit, noffset, "hashed-strings", NULL); + if (strings) { + fdt_regions[count].offset = fdt_off_dt_strings(fit) + + fdt32_to_cpu(strings[0]); + fdt_regions[count].size = fdt32_to_cpu(strings[1]); + count++; + } + + /* Allocate the region list on the stack */ + struct image_region region[count]; + + fit_region_make_list(fit, fdt_regions, count, region); + if (info.algo->verify(&info, region, count, fit_value, + fit_value_len)) { + *err_msgp = "Verification failed"; + return -1; + } + + return 0; +} + +static int fit_config_verify_sig(const void *fit, int conf_noffset, + const void *sig_blob, int sig_offset) +{ + int noffset; + char *err_msg = ""; + int verified = 0; + int ret; + + /* Process all hash subnodes of the component conf node */ + for (noffset = fdt_first_subnode(fit, conf_noffset); + noffset >= 0; + noffset = fdt_next_subnode(fit, noffset)) { + const char *name = fit_get_name(fit, noffset, NULL); + + if (!strncmp(name, FIT_SIG_NODENAME, + strlen(FIT_SIG_NODENAME))) { + ret = fit_config_check_sig(fit, noffset, sig_offset, + &err_msg); + if (ret) { + puts("- "); + } else { + puts("+ "); + verified = 1; + break; + } + } + } + + if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) { + err_msg = "Corrupted or truncated tree"; + goto error; + } + + return verified ? 0 : -EPERM; + +error: + printf(" error!\n%s for '%s' hash node in '%s' config node\n", + err_msg, fit_get_name(fit, noffset, NULL), + fit_get_name(fit, conf_noffset, NULL)); + return -1; +} + +int fit_config_verify_required_sigs(const void *fit, int conf_noffset, + const void *sig_blob) +{ + int noffset; + int sig_node; + + /* Work out what we need to verify */ + sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME); + if (sig_node < 0) { + debug("%s: No signature node found: %s\n", __func__, + fdt_strerror(sig_node)); + return 0; + } + + for (noffset = fdt_first_subnode(sig_blob, sig_node); + noffset >= 0; + noffset = fdt_next_subnode(sig_blob, noffset)) { + const char *required; + int ret; + + required = fdt_getprop(sig_blob, noffset, "required", NULL); + if (!required || strcmp(required, "conf")) + continue; + ret = fit_config_verify_sig(fit, conf_noffset, sig_blob, + noffset); + if (ret) { + printf("Failed to verify required signature '%s'\n", + fit_get_name(sig_blob, noffset, NULL)); + return ret; + } + } + + return 0; +} + +int fit_config_verify(const void *fit, int conf_noffset) +{ + return !fit_config_verify_required_sigs(fit, conf_noffset, + gd_fdt_blob()); +} diff --git a/doc/uImage.FIT/sign-configs.its b/doc/uImage.FIT/sign-configs.its new file mode 100644 index 0000000..3c17f04 --- /dev/null +++ b/doc/uImage.FIT/sign-configs.its @@ -0,0 +1,45 @@ +/dts-v1/; + +/ { + description = "Chrome OS kernel image with one or more FDT blobs"; + #address-cells = <1>; + + images { + kernel@1 { + data = /incbin/("test-kernel.bin"); + type = "kernel_noload"; + arch = "sandbox"; + os = "linux"; + compression = "lzo"; + load = <0x4>; + entry = <0x8>; + kernel-version = <1>; + hash@1 { + algo = "sha1"; + }; + }; + fdt@1 { + description = "snow"; + data = /incbin/("sandbox-kernel.dtb"); + type = "flat_dt"; + arch = "sandbox"; + compression = "none"; + fdt-version = <1>; + hash@1 { + algo = "sha1"; + }; + }; + }; + configurations { + default = "conf@1"; + conf@1 { + kernel = "kernel@1"; + fdt = "fdt@1"; + signature@1 { + algo = "sha1,rsa2048"; + key-name-hint = "dev"; + sign-images = "fdt", "kernel"; + }; + }; + }; +}; diff --git a/doc/uImage.FIT/signature.txt b/doc/uImage.FIT/signature.txt index 0d145e0..bc9f3fa 100644 --- a/doc/uImage.FIT/signature.txt +++ b/doc/uImage.FIT/signature.txt @@ -105,8 +105,27 @@ When the image is signed, the following properties are optional:

- comment: Additional information about the signer or image

+For config bindings (see Signed Configurations below), the following +additional properties are optional:

-Example: See sign-images.its for an example image tree source file. +- sign-images: A list of images to sign, each being a property of the conf +node that contains then. The default is "kernel,fdt" which means that these +two images will be looked up in the config and signed if present. + +For config bindings, these properties are added by the signer: + +- hashed-nodes: A list of nodes which were hashed by the signer. Each is + a string - the full path to node. A typical value might be: + + hashed-nodes = "/", "/configurations/conf@1", "/images/kernel@1", + "/images/kernel@1/hash@1", "/images/fdt@1", + "/images/fdt@1/hash@1"; + +- hashed-strings: The start and size of the string region of the FIT that + was hashed + +Example: See sign-images.its for an example image tree source file and +sign-configs.its for config signing.

Public Key Storage @@ -144,6 +163,153 @@ For RSA the following are mandatory: - rsa,n0-inverse: -1 / modulus[0] mod 2^32

+Signed Configurations +--------------------- +While signing images is useful, it does not provide complete protection +against several types of attack. For example, it it possible to create a +FIT with the same signed images, but with the configuration changed such +that a different one is selected (mix and match attack). It is also possible +to substitute a signed image from an older FIT version into a newer FIT +(roll-back attack). + +As an example, consider this FIT: + +/ { + images { + kernel@1 { + data = <data for kernel1> + signature@1 { + algo = "sha1,rsa2048"; + value = <...kernel signature 1...> + }; + }; + kernel@2 { + data = <data for kernel2> + signature@1 { + algo = "sha1,rsa2048"; + value = <...kernel signature 2...> + }; + }; + fdt@1 { + data = <data for fdt1>; + signature@1 { + algo = "sha1,rsa2048"; + vaue = <...fdt signature 1...> + }; + }; + fdt@2 { + data = <data for fdt2>; + signature@1 { + algo = "sha1,rsa2048"; + vaue = <...fdt signature 2...> + }; + }; + }; + configurations { + default = "conf@1"; + conf@1 { + kernel = "kernel@1"; + fdt = "fdt@1"; + }; + conf@1 { + kernel = "kernel@2"; + fdt = "fdt@2"; + }; + }; +}; + +Since both kernels are signed it is easy for an attacker to add a new +configuration 3 with kernel 1 and fdt 2: + + configurations { + default = "conf@1"; + conf@1 { + kernel = "kernel@1"; + fdt = "fdt@1"; + }; + conf@1 { + kernel = "kernel@2"; + fdt = "fdt@2"; + }; + conf@3 { + kernel = "kernel@1"; + fdt = "fdt@2"; + }; + }; + +With signed images, nothing protects against this. Whether it gains an +advantage for the attacker is debatable, but it is not secure. + +To solved this problem, we support signed configurations. In this case it +is the configurations that are signed, not the image. Each image has its +own hash, and we include the hash in the configuration signature. + +So the above example is adjusted to look like this: + +/ { + images { + kernel@1 { + data = <data for kernel1> + hash@1 { + algo = "sha1"; + value = <...kernel hash 1...> + }; + }; + kernel@2 { + data = <data for kernel2> + hash@1 { + algo = "sha1"; + value = <...kernel hash 2...> + }; + }; + fdt@1 { + data = <data for fdt1>; + hash@1 { + algo = "sha1"; + value = <...fdt hash 1...> + }; + }; + fdt@2 { + data = <data for fdt2>; + hash@1 { + algo = "sha1"; + value = <...fdt hash 2...> + }; + }; + }; + configurations { + default = "conf@1"; + conf@1 { + kernel = "kernel@1"; + fdt = "fdt@1"; + signature@1 { + algo = "sha1,rsa2048"; + value = <...conf 1 signature...>; + }; + }; + conf@2 { + kernel = "kernel@2"; + fdt = "fdt@2"; + signature@1 { + algo = "sha1,rsa2048"; + value = <...conf 1 signature...>; + }; + }; + }; +}; + + +You can see that we have added hashes for all images (since they are no +longer signed), and a signature to each configuration. In the above example, +mkimage will sign configurations/conf@1, the kernel and fdt that are +pointed to by the configuration (/images/kernel@1, /images/kernel@1/hash@1, +/images/fdt@1, /images/fdt@1/hash@1) and the root structure of the image +(so that it isn't possible to add or remove root nodes). The signature is +written into /configurations/conf@1/signature@1/value. It can easily be +verified later even if the FIT has been signed with other keys in the +meantime. + + Verification ------------ FITs are verified when loaded. After the configuration is selected a list diff --git a/include/image.h b/include/image.h index da7b9a0..2614918 100644 --- a/include/image.h +++ b/include/image.h @@ -964,6 +964,22 @@ int fit_image_verify_required_sigs(const void *fit, int image_noffset, int fit_image_check_sig(const void *fit, int noffset, const void *data, size_t size, int required_keynode, char **err_msgp);

+/** + * fit_region_make_list() - Make a list of regions to hash + * + * Given a list of FIT regions (offset, size) provided by libfdt, create + * a list of regions (void *, size) for use by the signature creationg + * and verification code. + * + * @fit: FIT image to process + * @fdt_regions: Regions as returned by libfdt + * @count: Number of regions returned by libfdt + * @region: Place to put list of regions (NULL to allocate it) + * @return pointer to list of regions, or NULL if out of memory + */ +struct image_region *fit_region_make_list(const void *fit, + struct fdt_region *fdt_regions, int count, + struct image_region *region);

static inline int fit_image_check_target_arch(const void *fdt, int node) { diff --git a/tools/image-host.c b/tools/image-host.c index 7aebc29..932384b 100644 --- a/tools/image-host.c +++ b/tools/image-host.c @@ -341,10 +341,326 @@ int fit_image_add_verification_data(const char *keydir, void *keydest, return 0; }

+struct strlist { + int count; + char **strings; +}; + +static void strlist_init(struct strlist *list) +{ + memset(list, '\0', sizeof(*list)); +} + +static void strlist_free(struct strlist *list) +{ + int i; + + for (i = 0; i < list->count; i++) + free(list->strings[i]); + free(list->strings); +} + +static int strlist_add(struct strlist *list, const char *str) +{ + char *dup; + + dup = strdup(str); + list->strings = realloc(list->strings, + (list->count + 1) * sizeof(char *)); + if (!list || !str) + return -1; + list->strings[list->count++] = dup; + + return 0; +} + +static const char *fit_config_get_image_list(void *fit, int noffset, + int *lenp, int *allow_missingp) +{ + static const char default_list[] = FIT_KERNEL_PROP "\0" + FIT_FDT_PROP; + const char *prop; + + /* If there is an "image" property, use that */ + prop = fdt_getprop(fit, noffset, "sign-images", lenp); + if (prop) { + *allow_missingp = 0; + return *lenp ? prop : NULL; + } + + /* Default image list */ + *allow_missingp = 1; + *lenp = sizeof(default_list); + + return default_list; +} + +static int fit_config_get_hash_list(void *fit, int conf_noffset, + int sig_offset, struct strlist *node_inc) +{ + int allow_missing; + const char *prop, *iname, *end; + const char *conf_name, *sig_name; + char name[200], path[200]; + int image_count; + int ret, len; + + conf_name = fit_get_name(fit, conf_noffset, NULL); + sig_name = fit_get_name(fit, sig_offset, NULL); + + /* + * Build a list of nodes we need to hash. We always need the root + * node and the configuration. + */ + strlist_init(node_inc); + snprintf(name, sizeof(name), "%s/%s", FIT_CONFS_PATH, conf_name); + if (strlist_add(node_inc, "/") || + strlist_add(node_inc, name)) + goto err_mem; + + /* Get a list of images that we intend to sign */ + prop = fit_config_get_image_list(fit, conf_noffset, &len, + &allow_missing); + if (!prop) + return 0; + + /* Locate the images */ + end = prop + len; + image_count = 0; + for (iname = prop; iname < end; iname += strlen(iname) + 1) { + int noffset; + int image_noffset; + int hash_count; + + image_noffset = fit_conf_get_prop_node(fit, conf_noffset, + iname); + if (image_noffset < 0) { + printf("Failed to find image '%s' in configuration '%s/%s'\n", + iname, conf_name, sig_name); + if (allow_missing) + continue; + + return -ENOENT; + } + + ret = fdt_get_path(fit, image_noffset, path, sizeof(path)); + if (ret < 0) + goto err_path; + if (strlist_add(node_inc, path)) + goto err_mem; + + snprintf(name, sizeof(name), "%s/%s", FIT_CONFS_PATH, + conf_name); + + /* Add all this image's hashes */ + hash_count = 0; + for (noffset = fdt_first_subnode(fit, image_noffset); + noffset >= 0; + noffset = fdt_next_subnode(fit, noffset)) { + const char *name = fit_get_name(fit, noffset, NULL); + + if (strncmp(name, FIT_HASH_NODENAME, + strlen(FIT_HASH_NODENAME))) + continue; + ret = fdt_get_path(fit, noffset, path, sizeof(path)); + if (ret < 0) + goto err_path; + if (strlist_add(node_inc, path)) + goto err_mem; + hash_count++; + } + + if (!hash_count) { + printf("Failed to find any hash nodes in configuration '%s/%s' image '%s' - without these it is not possible to verify this image\n", + conf_name, sig_name, iname); + return -ENOMSG; + } + + image_count++; + } + + if (!image_count) { + printf("Failed to find any images for configuration '%s/%s'\n", + conf_name, sig_name); + return -ENOMSG; + } + + return 0; + +err_mem: + printf("Out of memory processing configuration '%s/%s'\n", conf_name, + sig_name); + return -ENOMEM; + +err_path: + printf("Failed to get path for image '%s' in configuration '%s/%s': %s\n", + iname, conf_name, sig_name, fdt_strerror(ret)); + return -ENOENT; +} + +static int fit_config_get_data(void *fit, int conf_noffset, int noffset, + struct image_region **regionp, int *region_countp, + char **region_propp, int *region_proplen) +{ + char * const exc_prop[] = {"data"}; + struct strlist node_inc; + struct image_region *region; + struct fdt_region fdt_regions[100]; + const char *conf_name, *sig_name; + char path[200]; + int count, i; + char *region_prop; + int ret, len; + + conf_name = fit_get_name(fit, conf_noffset, NULL); + sig_name = fit_get_name(fit, conf_noffset, NULL); + debug("%s: conf='%s', sig='%s'\n", __func__, conf_name, sig_name); + + /* Get a list of nodes we want to hash */ + ret = fit_config_get_hash_list(fit, conf_noffset, noffset, &node_inc); + if (ret) + return ret; + + /* Get a list of regions to hash */ + count = fdt_find_regions(fit, node_inc.strings, node_inc.count, + exc_prop, ARRAY_SIZE(exc_prop), + fdt_regions, ARRAY_SIZE(fdt_regions), + path, sizeof(path), 1); + if (count < 0) { + printf("Failed to hash configuration '%s/%s': %s\n", conf_name, + sig_name, fdt_strerror(ret)); + return -EIO; + } + if (count == 0) { + printf("No data to hash for configuration '%s/%s': %s\n", + conf_name, sig_name, fdt_strerror(ret)); + return -EINVAL; + } + + /* Build our list of data blocks */ + region = fit_region_make_list(fit, fdt_regions, count, NULL); + if (!region) { + printf("Out of memory hashing configuration '%s/%s'\n", + conf_name, sig_name); + return -ENOMEM; + } + + /* Create a list of all hashed properties */ + debug("Hash nodes:\n"); + for (i = len = 0; i < node_inc.count; i++) { + debug(" %s\n", node_inc.strings[i]); + len += strlen(node_inc.strings[i]) + 1; + } + region_prop = malloc(len); + if (!region_prop) { + printf("Out of memory setting up regions for configuration '%s/%s'\n", + conf_name, sig_name); + return -ENOMEM; + } + for (i = len = 0; i < node_inc.count; + len += strlen(node_inc.strings[i]) + 1, i++) + strcpy(region_prop + len, node_inc.strings[i]); + strlist_free(&node_inc); + + *region_countp = count; + *regionp = region; + *region_propp = region_prop; + *region_proplen = len; + + return 0; +} + +static int fit_config_process_sig(const char *keydir, void *keydest, + void *fit, const char *conf_name, int conf_noffset, + int noffset, const char *comment, int require_keys) +{ + struct image_sign_info info; + const char *node_name; + struct image_region *region; + char *region_prop; + int region_proplen; + int region_count; + uint8_t *value; + uint value_len; + int ret; + + node_name = fit_get_name(fit, noffset, NULL); + if (fit_config_get_data(fit, conf_noffset, noffset, &region, + &region_count, &region_prop, &region_proplen)) + return -1; + + if (fit_image_setup_sig(&info, keydir, fit, conf_name, noffset, + require_keys ? "conf" : NULL)) + return -1; + + ret = info.algo->sign(&info, region, region_count, &value, &value_len); + free(region); + if (ret) { + printf("Failed to sign '%s' signature node in '%s' conf node\n", + node_name, conf_name); + + /* We allow keys to be missing */ + if (ret == -ENOENT) + return 0; + return -1; + } + + if (fit_image_write_sig(fit, noffset, value, value_len, comment, + region_prop, region_proplen)) { + printf("Can't write signature for '%s' signature node in '%s' conf node\n", + node_name, conf_name); + return -1; + } + free(value); + free(region_prop); + + /* Get keyname again, as FDT has changed and invalidated our pointer */ + info.keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL); + + /* Write the public key into the supplied FDT file */ + if (keydest && info.algo->add_verify_data(&info, keydest)) { + printf("Failed to add verification data for '%s' signature node in '%s' image node\n", + node_name, conf_name); + return -1; + } + + return 0; +} + +static int fit_config_add_verification_data(const char *keydir, void *keydest, + void *fit, int conf_noffset, const char *comment, + int require_keys) +{ + const char *conf_name; + int noffset; + + conf_name = fit_get_name(fit, conf_noffset, NULL); + + /* Process all hash subnodes of the configuration node */ + for (noffset = fdt_first_subnode(fit, conf_noffset); + noffset >= 0; + noffset = fdt_next_subnode(fit, noffset)) { + const char *node_name; + int ret = 0; + + node_name = fit_get_name(fit, noffset, NULL); + if (!strncmp(node_name, FIT_SIG_NODENAME, + strlen(FIT_SIG_NODENAME))) { + ret = fit_config_process_sig(keydir, keydest, + fit, conf_name, conf_noffset, noffset, comment, + require_keys); + } + if (ret) + return ret; + } + + return 0; +} + int fit_add_verification_data(const char *keydir, void *keydest, void *fit, const char *comment, int require_keys) { - int images_noffset; + int images_noffset, confs_noffset; int noffset; int ret;

@@ -370,5 +686,28 @@ int fit_add_verification_data(const char *keydir, void *keydest, void *fit, return ret; }

+ /* If there are no keys, we can't sign configurations */ + if (!IMAGE_ENABLE_SIGN || !keydir) + return 0; + + /* Find configurations parent node offset */ + confs_noffset = fdt_path_offset(fit, FIT_CONFS_PATH); + if (confs_noffset < 0) { + printf("Can't find images parent node '%s' (%s)\n", + FIT_IMAGES_PATH, fdt_strerror(confs_noffset)); + return -ENOENT; + } + + /* Process its subnodes, print out component images details */ + for (noffset = fdt_first_subnode(fit, confs_noffset); + noffset >= 0; + noffset = fdt_next_subnode(fit, noffset)) { + ret = fit_config_add_verification_data(keydir, keydest, + fit, noffset, comment, + require_keys); + if (ret) + return ret; + } + return 0; }

Add a description of how to implement verified boot using signed FIT images, and a simple test which verifies operation on sandbox.

The test signs a FIT image and verifies it, then signs a FIT configuration and verifies it. Then it corrupts the signature to check that this is detected.

Signed-off-by: Simon Glass sjg@chromium.org --- Changes in v3: - Fix 'compile' typo - Rebase to master

Changes in v2: - Update README to fix typos - Use U-Boot's -c option instead of hard-coding a boot script

doc/uImage.FIT/verified-boot.txt | 104 ++++++++++++++++++++++++++++++++ test/vboot/.gitignore | 3 + test/vboot/sandbox-kernel.dts | 7 +++ test/vboot/sandbox-u-boot.dts | 7 +++ test/vboot/sign-configs.its | 45 ++++++++++++++ test/vboot/sign-images.its | 42 +++++++++++++ test/vboot/vboot_test.sh | 126 +++++++++++++++++++++++++++++++++++++++ 7 files changed, 334 insertions(+) create mode 100644 doc/uImage.FIT/verified-boot.txt create mode 100644 test/vboot/.gitignore create mode 100644 test/vboot/sandbox-kernel.dts create mode 100644 test/vboot/sandbox-u-boot.dts create mode 100644 test/vboot/sign-configs.its create mode 100644 test/vboot/sign-images.its create mode 100755 test/vboot/vboot_test.sh

diff --git a/doc/uImage.FIT/verified-boot.txt b/doc/uImage.FIT/verified-boot.txt new file mode 100644 index 0000000..3c83fbc --- /dev/null +++ b/doc/uImage.FIT/verified-boot.txt @@ -0,0 +1,104 @@ +U-Boot Verified Boot +==================== + +Introduction +------------ +Verified boot here means the verification of all software loaded into a +machine during the boot process to ensure that it is authorised and correct +for that machine. + +Verified boot extends from the moment of system reset to as far as you wish +into the boot process. An example might be loading U-Boot from read-only +memory, then loading a signed kernel, then using the kernel's dm-verity +driver to mount a signed root filesystem. + +A key point is that it is possible to field-upgrade the software on machines +which use verified boot. Since the machine will only run software that has +been correctly signed, it is safe to read software from an updatable medium. +It is also possible to add a secondary signed firmware image, in read-write +memory, so that firmware can easily be upgraded in a secure manner. + + +Signing +------- +Verified boot uses cryptographic algorithms to 'sign' software images. +Images are signed using a private key known only to the signer, but can +be verified using a public key. As its name suggests the public key can be +made available without risk to the verification process. The private and +public keys are mathematically related. For more information on how this +works look up "public key cryptography" and "RSA" (a particular algorithm). + +The signing and verification process looks something like this: + + + Signing Verification + ======= ============ + + +--------------+ * + | RSA key pair | * +---------------+ + | .key .crt | * | Public key in | + +--------------+ +------> public key ----->| trusted place | + | | * +---------------+ + | | * | + v | * v + +---------+ | * +--------------+ + | |----------+ * | | + | signer | * | U-Boot | + | |----------+ * | signature |--> yes/no + +---------+ | * | verification | + ^ | * | | + | | * +--------------+ + | | * ^ + +----------+ | * | + | Software | +----> signed image -------------+ + | image | * + +----------+ * + + +The signature algorithm relies only on the public key to do its work. Using +this key it checks the signature that it finds in the image. If it verifies +then we know that the image is OK. + +The public key from the signer allows us to verify and therefore trust +software from updatable memory. + +It is critical that the public key be secure and cannot be tampered with. +It can be stored in read-only memory, or perhaps protected by other on-chip +crypto provided by some modern SOCs. If the public key can ben changed, then +the verification is worthless. + + +Chaining Images +--------------- +The above method works for a signer providing images to a run-time U-Boot. +It is also possible to extend this scheme to a second level, like this: + +1. Master private key is used by the signer to sign a first-stage image. +2. Master public key is placed in read-only memory. +2. Secondary private key is created and used to sign second-stage images. +3. Secondary public key is placed in first stage images +4. We use the master public key to verify the first-stage image. We then +use the secondary public key in the first-stage image to verify the second- +state image. +5. This chaining process can go on indefinitely. It is recommended to use a +different key at each stage, so that a compromise in one place will not +affect the whole change. + + +Flattened Image Tree (FIT) +-------------------------- +The FIT format is alreay widely used in U-Boot. It is a flattened device +tree (FDT) in a particular format, with images contained within. FITs +include hashes to verify images, so it is relatively straightforward to +add signatures as well. + +The public key can be stored in U-Boot's CONFIG_OF_CONTROL device tree in +a standard place. Then when a FIT it loaded it can be verified using that +public key. Multiple keys and multiple signatures are supported. + +See signature.txt for more information. + + +Simon Glass +sjg@chromium.org +1-1-13 diff --git a/test/vboot/.gitignore b/test/vboot/.gitignore new file mode 100644 index 0000000..4631242 --- /dev/null +++ b/test/vboot/.gitignore @@ -0,0 +1,3 @@ +/*.dtb +/test.fit +/dev-keys diff --git a/test/vboot/sandbox-kernel.dts b/test/vboot/sandbox-kernel.dts new file mode 100644 index 0000000..a1e853c --- /dev/null +++ b/test/vboot/sandbox-kernel.dts @@ -0,0 +1,7 @@ +/dts-v1/; + +/ { + model = "Sandbox Verified Boot Test"; + compatible = "sandbox"; + +}; diff --git a/test/vboot/sandbox-u-boot.dts b/test/vboot/sandbox-u-boot.dts new file mode 100644 index 0000000..a1e853c --- /dev/null +++ b/test/vboot/sandbox-u-boot.dts @@ -0,0 +1,7 @@ +/dts-v1/; + +/ { + model = "Sandbox Verified Boot Test"; + compatible = "sandbox"; + +}; diff --git a/test/vboot/sign-configs.its b/test/vboot/sign-configs.its new file mode 100644 index 0000000..db2ed79 --- /dev/null +++ b/test/vboot/sign-configs.its @@ -0,0 +1,45 @@ +/dts-v1/; + +/ { + description = "Chrome OS kernel image with one or more FDT blobs"; + #address-cells = <1>; + + images { + kernel@1 { + data = /incbin/("test-kernel.bin"); + type = "kernel_noload"; + arch = "sandbox"; + os = "linux"; + compression = "none"; + load = <0x4>; + entry = <0x8>; + kernel-version = <1>; + hash@1 { + algo = "sha1"; + }; + }; + fdt@1 { + description = "snow"; + data = /incbin/("sandbox-kernel.dtb"); + type = "flat_dt"; + arch = "sandbox"; + compression = "none"; + fdt-version = <1>; + hash@1 { + algo = "sha1"; + }; + }; + }; + configurations { + default = "conf@1"; + conf@1 { + kernel = "kernel@1"; + fdt = "fdt@1"; + signature@1 { + algo = "sha1,rsa2048"; + key-name-hint = "dev"; + sign-images = "fdt", "kernel"; + }; + }; + }; +}; diff --git a/test/vboot/sign-images.its b/test/vboot/sign-images.its new file mode 100644 index 0000000..f69326a --- /dev/null +++ b/test/vboot/sign-images.its @@ -0,0 +1,42 @@ +/dts-v1/; + +/ { + description = "Chrome OS kernel image with one or more FDT blobs"; + #address-cells = <1>; + + images { + kernel@1 { + data = /incbin/("test-kernel.bin"); + type = "kernel_noload"; + arch = "sandbox"; + os = "linux"; + compression = "none"; + load = <0x4>; + entry = <0x8>; + kernel-version = <1>; + signature@1 { + algo = "sha1,rsa2048"; + key-name-hint = "dev"; + }; + }; + fdt@1 { + description = "snow"; + data = /incbin/("sandbox-kernel.dtb"); + type = "flat_dt"; + arch = "sandbox"; + compression = "none"; + fdt-version = <1>; + signature@1 { + algo = "sha1,rsa2048"; + key-name-hint = "dev"; + }; + }; + }; + configurations { + default = "conf@1"; + conf@1 { + kernel = "kernel@1"; + fdt = "fdt@1"; + }; + }; +}; diff --git a/test/vboot/vboot_test.sh b/test/vboot/vboot_test.sh new file mode 100755 index 0000000..c3cfade --- /dev/null +++ b/test/vboot/vboot_test.sh @@ -0,0 +1,126 @@ +#!/bin/sh +# +# Copyright (c) 2013, Google Inc. +# +# Simple Verified Boot Test Script +# +# This program is free software; you can redistribute it and/or +# modify it under the terms of the GNU General Public License as +# published by the Free Software Foundation; either version 2 of +# the License, or (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program; if not, write to the Free Software +# Foundation, Inc., 59 Temple Place, Suite 330, Boston, +# MA 02111-1307 USA + +set -e + +# Run U-Boot and report the result +# Args: +# $1: Test message +run_uboot() { + echo -n "Test Verified Boot Run: $1: " + ${uboot} -d sandbox-u-boot.dtb >${tmp} -c ' +sb load host 0 100 test.fit; +fdt addr 100; +bootm 100; +reset' + if ! grep -q "$2" ${tmp}; then + echo + echo "Verified boot key check failed, output follows:" + cat ${tmp} + false + else + echo "OK" + fi +} + +echo "Simple Verified Boot Test" +echo "=========================" +echo +echo "Please see doc/uImage.FIT/verified-boot.txt for more information" +echo + +err=0 +tmp=/tmp/vboot_test.$$ + +dir=$(dirname $0) + +if [ -z ${O} ]; then + O=. +fi +O=$(readlink -f ${O}) + +dtc="-I dts -O dtb -p 2000" +uboot="${O}/u-boot" +mkimage="${O}/tools/mkimage" +keys="${dir}/dev-keys" +echo ${mkimage} -D "${dtc}" + +echo "Build keys" +mkdir -p ${keys} + +# Create an RSA key pair +openssl genrsa -F4 -out ${keys}/dev.key 2048 2>/dev/null + +# Create a certificate containing the public key +openssl req -batch -new -x509 -key ${keys}/dev.key -out ${keys}/dev.crt + +pushd ${dir} >/dev/null + +# Compile our device tree files for kernel and U-Boot (CONFIG_OF_CONTROL) +dtc -p 0x1000 sandbox-kernel.dts -O dtb -o sandbox-kernel.dtb +dtc -p 0x1000 sandbox-u-boot.dts -O dtb -o sandbox-u-boot.dtb + +# Create a number kernel image with zeroes +head -c 5000 /dev/zero >test-kernel.bin + +# Build the FIT, but don't sign anything yet +echo Build FIT with signed images +${mkimage} -D "${dtc}" -f sign-images.its test.fit >${tmp} + +run_uboot "unsigned signatures:" "dev-" + +# Sign images with our dev keys +echo Sign images +${mkimage} -D "${dtc}" -F -k dev-keys -K sandbox-u-boot.dtb -r test.fit >${tmp} + +run_uboot "signed images" "dev+" + + +# Create a fresh .dtb without the public keys +dtc -p 0x1000 sandbox-u-boot.dts -O dtb -o sandbox-u-boot.dtb + +echo Build FIT with signed configuration +${mkimage} -D "${dtc}" -f sign-configs.its test.fit >${tmp} + +run_uboot "unsigned config" "sha1+ OK" + +# Sign images with our dev keys +echo Sign images +${mkimage} -D "${dtc}" -F -k dev-keys -K sandbox-u-boot.dtb -r test.fit >${tmp} + +run_uboot "signed config" "dev+" + +# Increment the first byte of the signature, which should cause failure +sig=$(fdtget -t bx test.fit /configurations/conf@1/signature@1 value) +newbyte=$(printf %x $((0x${sig:0:2} + 1))) +sig="${newbyte} ${sig:2}" +fdtput -t bx test.fit /configurations/conf@1/signature@1 value ${sig} + +run_uboot "signed config with bad hash" "Bad Data Hash" + +popd >/dev/null + +echo +if ${ok}; then + echo "Test passed" +else + echo "Test failed" +fi