The file, pkcs7_verify.c, will now be imported from linux code (crypto/asymmetric_keys/pkcs7_verify.c) and modified to fit into U-Boot environment.
In particular, pkcs7_verify_one() function will be used in a later patch to rework signature verification logic aiming to support intermediate certificates in "chain of trust."
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- lib/crypto/Kconfig | 3 + lib/crypto/Makefile | 1 + lib/crypto/pkcs7_verify.c | 521 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 525 insertions(+) create mode 100644 lib/crypto/pkcs7_verify.c
diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig index 2b221b915aa6..6369bafac07b 100644 --- a/lib/crypto/Kconfig +++ b/lib/crypto/Kconfig @@ -49,4 +49,7 @@ config PKCS7_MESSAGE_PARSER This option provides support for parsing PKCS#7 format messages for signature data and provides the ability to verify the signature.
+config PKCS7_VERIFY + bool + endif # ASYMMETRIC_KEY_TYPE diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile index 8267fee0a7b8..f3a414525d2a 100644 --- a/lib/crypto/Makefile +++ b/lib/crypto/Makefile @@ -44,6 +44,7 @@ obj-$(CONFIG_PKCS7_MESSAGE_PARSER) += pkcs7_message.o pkcs7_message-y := \ pkcs7.asn1.o \ pkcs7_parser.o +obj-$(CONFIG_PKCS7_VERIFY) += pkcs7_verify.o
$(obj)/pkcs7_parser.o: $(obj)/pkcs7.asn1.h $(obj)/pkcs7.asn1.o: $(obj)/pkcs7.asn1.c $(obj)/pkcs7.asn1.h diff --git a/lib/crypto/pkcs7_verify.c b/lib/crypto/pkcs7_verify.c new file mode 100644 index 000000000000..a893fa3b586b --- /dev/null +++ b/lib/crypto/pkcs7_verify.c @@ -0,0 +1,521 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Verify the signature on a PKCS#7 message. + * + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#define pr_fmt(fmt) "PKCS7: "fmt +#ifdef __UBOOT__ +#include <string.h> +#include <linux/bitops.h> +#include <linux/compat.h> +#include <linux/asn1.h> +#include <crypto/public_key.h> +#include <crypto/pkcs7_parser.h> +#else +#include <linux/kernel.h> +#include <linux/export.h> +#include <linux/slab.h> +#include <linux/err.h> +#include <linux/asn1.h> +#include <crypto/hash.h> +#include <crypto/hash_info.h> +#include <crypto/public_key.h> +#include "pkcs7_parser.h" +#endif + +/* + * Digest the relevant parts of the PKCS#7 data + */ +#ifdef __UBOOT__ +static int pkcs7_digest(struct pkcs7_message *pkcs7, + struct pkcs7_signed_info *sinfo) +{ + return 0; +} +#else +static int pkcs7_digest(struct pkcs7_message *pkcs7, + struct pkcs7_signed_info *sinfo) +{ + struct public_key_signature *sig = sinfo->sig; + struct crypto_shash *tfm; + struct shash_desc *desc; + size_t desc_size; + int ret; + + kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo); + + /* The digest was calculated already. */ + if (sig->digest) + return 0; + + if (!sinfo->sig->hash_algo) + return -ENOPKG; + + /* Allocate the hashing algorithm we're going to need and find out how + * big the hash operational data will be. + */ + tfm = crypto_alloc_shash(sinfo->sig->hash_algo, 0, 0); + if (IS_ERR(tfm)) + return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm); + + desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); + sig->digest_size = crypto_shash_digestsize(tfm); + + ret = -ENOMEM; + sig->digest = kmalloc(sig->digest_size, GFP_KERNEL); + if (!sig->digest) + goto error_no_desc; + + desc = kzalloc(desc_size, GFP_KERNEL); + if (!desc) + goto error_no_desc; + + desc->tfm = tfm; + + /* Digest the message [RFC2315 9.3] */ + ret = crypto_shash_digest(desc, pkcs7->data, pkcs7->data_len, + sig->digest); + if (ret < 0) + goto error; + pr_devel("MsgDigest = [%*ph]\n", 8, sig->digest); + + /* However, if there are authenticated attributes, there must be a + * message digest attribute amongst them which corresponds to the + * digest we just calculated. + */ + if (sinfo->authattrs) { + u8 tag; + + if (!sinfo->msgdigest) { + pr_warn("Sig %u: No messageDigest\n", sinfo->index); + ret = -EKEYREJECTED; + goto error; + } + + if (sinfo->msgdigest_len != sig->digest_size) { + pr_debug("Sig %u: Invalid digest size (%u)\n", + sinfo->index, sinfo->msgdigest_len); + ret = -EBADMSG; + goto error; + } + + if (memcmp(sig->digest, sinfo->msgdigest, + sinfo->msgdigest_len) != 0) { + pr_debug("Sig %u: Message digest doesn't match\n", + sinfo->index); + ret = -EKEYREJECTED; + goto error; + } + + /* We then calculate anew, using the authenticated attributes + * as the contents of the digest instead. Note that we need to + * convert the attributes from a CONT.0 into a SET before we + * hash it. + */ + memset(sig->digest, 0, sig->digest_size); + + ret = crypto_shash_init(desc); + if (ret < 0) + goto error; + tag = ASN1_CONS_BIT | ASN1_SET; + ret = crypto_shash_update(desc, &tag, 1); + if (ret < 0) + goto error; + ret = crypto_shash_finup(desc, sinfo->authattrs, + sinfo->authattrs_len, sig->digest); + if (ret < 0) + goto error; + pr_devel("AADigest = [%*ph]\n", 8, sig->digest); + } + +error: + kfree(desc); +error_no_desc: + crypto_free_shash(tfm); + kleave(" = %d", ret); + return ret; +} + +int pkcs7_get_digest(struct pkcs7_message *pkcs7, const u8 **buf, u32 *len, + enum hash_algo *hash_algo) +{ + struct pkcs7_signed_info *sinfo = pkcs7->signed_infos; + int i, ret; + + /* + * This function doesn't support messages with more than one signature. + */ + if (sinfo == NULL || sinfo->next != NULL) + return -EBADMSG; + + ret = pkcs7_digest(pkcs7, sinfo); + if (ret) + return ret; + + *buf = sinfo->sig->digest; + *len = sinfo->sig->digest_size; + + for (i = 0; i < HASH_ALGO__LAST; i++) + if (!strcmp(hash_algo_name[i], sinfo->sig->hash_algo)) { + *hash_algo = i; + break; + } + + return 0; +} +#endif /* !__UBOOT__ */ + +/* + * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7 + * uses the issuer's name and the issuing certificate serial number for + * matching purposes. These must match the certificate issuer's name (not + * subject's name) and the certificate serial number [RFC 2315 6.7]. + */ +static int pkcs7_find_key(struct pkcs7_message *pkcs7, + struct pkcs7_signed_info *sinfo) +{ + struct x509_certificate *x509; + unsigned certix = 1; + + kenter("%u", sinfo->index); + + for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) { + /* I'm _assuming_ that the generator of the PKCS#7 message will + * encode the fields from the X.509 cert in the same way in the + * PKCS#7 message - but I can't be 100% sure of that. It's + * possible this will need element-by-element comparison. + */ + if (!asymmetric_key_id_same(x509->id, sinfo->sig->auth_ids[0])) + continue; + pr_devel("Sig %u: Found cert serial match X.509[%u]\n", + sinfo->index, certix); + + if (strcmp(x509->pub->pkey_algo, sinfo->sig->pkey_algo) != 0) { + pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n", + sinfo->index); + continue; + } + + sinfo->signer = x509; + return 0; + } + + /* The relevant X.509 cert isn't found here, but it might be found in + * the trust keyring. + */ + pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n", + sinfo->index, + sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->data); + return 0; +} + +/* + * Verify the internal certificate chain as best we can. + */ +static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7, + struct pkcs7_signed_info *sinfo) +{ + struct public_key_signature *sig; + struct x509_certificate *x509 = sinfo->signer, *p; + struct asymmetric_key_id *auth; + int ret; + + kenter(""); + + for (p = pkcs7->certs; p; p = p->next) + p->seen = false; + + for (;;) { + pr_debug("verify %s: %*phN\n", + x509->subject, + x509->raw_serial_size, x509->raw_serial); + x509->seen = true; + + if (x509->blacklisted) { + /* If this cert is blacklisted, then mark everything + * that depends on this as blacklisted too. + */ + sinfo->blacklisted = true; + for (p = sinfo->signer; p != x509; p = p->signer) + p->blacklisted = true; + pr_debug("- blacklisted\n"); + return 0; + } + + if (x509->unsupported_key) + goto unsupported_crypto_in_x509; + + pr_debug("- issuer %s\n", x509->issuer); + sig = x509->sig; + if (sig->auth_ids[0]) + pr_debug("- authkeyid.id %*phN\n", + sig->auth_ids[0]->len, sig->auth_ids[0]->data); + if (sig->auth_ids[1]) + pr_debug("- authkeyid.skid %*phN\n", + sig->auth_ids[1]->len, sig->auth_ids[1]->data); + + if (x509->self_signed) { + /* If there's no authority certificate specified, then + * the certificate must be self-signed and is the root + * of the chain. Likewise if the cert is its own + * authority. + */ + if (x509->unsupported_sig) + goto unsupported_crypto_in_x509; + x509->signer = x509; + pr_debug("- self-signed\n"); + return 0; + } + + /* Look through the X.509 certificates in the PKCS#7 message's + * list to see if the next one is there. + */ + auth = sig->auth_ids[0]; + if (auth) { + pr_debug("- want %*phN\n", auth->len, auth->data); + for (p = pkcs7->certs; p; p = p->next) { + pr_debug("- cmp [%u] %*phN\n", + p->index, p->id->len, p->id->data); + if (asymmetric_key_id_same(p->id, auth)) + goto found_issuer_check_skid; + } + } else if (sig->auth_ids[1]) { + auth = sig->auth_ids[1]; + pr_debug("- want %*phN\n", auth->len, auth->data); + for (p = pkcs7->certs; p; p = p->next) { + if (!p->skid) + continue; + pr_debug("- cmp [%u] %*phN\n", + p->index, p->skid->len, p->skid->data); + if (asymmetric_key_id_same(p->skid, auth)) + goto found_issuer; + } + } + + /* We didn't find the root of this chain */ + pr_debug("- top\n"); + return 0; + + found_issuer_check_skid: + /* We matched issuer + serialNumber, but if there's an + * authKeyId.keyId, that must match the CA subjKeyId also. + */ + if (sig->auth_ids[1] && + !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) { + pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n", + sinfo->index, x509->index, p->index); + return -EKEYREJECTED; + } + found_issuer: + pr_debug("- subject %s\n", p->subject); + if (p->seen) { + pr_warn("Sig %u: X.509 chain contains loop\n", + sinfo->index); + return 0; + } + ret = public_key_verify_signature(p->pub, x509->sig); + if (ret < 0) + return ret; + x509->signer = p; + if (x509 == p) { + pr_debug("- self-signed\n"); + return 0; + } + x509 = p; +#ifndef __UBOOT__ + might_sleep(); +#endif + } + +unsupported_crypto_in_x509: + /* Just prune the certificate chain at this point if we lack some + * crypto module to go further. Note, however, we don't want to set + * sinfo->unsupported_crypto as the signed info block may still be + * validatable against an X.509 cert lower in the chain that we have a + * trusted copy of. + */ + return 0; +} + +/* + * Verify one signed information block from a PKCS#7 message. + */ +#ifndef __UBOOT__ +static +#endif +int pkcs7_verify_one(struct pkcs7_message *pkcs7, + struct pkcs7_signed_info *sinfo) +{ + int ret; + + kenter(",%u", sinfo->index); + + /* First of all, digest the data in the PKCS#7 message and the + * signed information block + */ + ret = pkcs7_digest(pkcs7, sinfo); + if (ret < 0) + return ret; + + /* Find the key for the signature if there is one */ + ret = pkcs7_find_key(pkcs7, sinfo); + if (ret < 0) + return ret; + + if (!sinfo->signer) + return 0; + + pr_devel("Using X.509[%u] for sig %u\n", + sinfo->signer->index, sinfo->index); + + /* Check that the PKCS#7 signing time is valid according to the X.509 + * certificate. We can't, however, check against the system clock + * since that may not have been set yet and may be wrong. + */ + if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) { + if (sinfo->signing_time < sinfo->signer->valid_from || + sinfo->signing_time > sinfo->signer->valid_to) { + pr_warn("Message signed outside of X.509 validity window\n"); + return -EKEYREJECTED; + } + } + + /* Verify the PKCS#7 binary against the key */ + ret = public_key_verify_signature(sinfo->signer->pub, sinfo->sig); + if (ret < 0) + return ret; + + pr_devel("Verified signature %u\n", sinfo->index); + + /* Verify the internal certificate chain */ + return pkcs7_verify_sig_chain(pkcs7, sinfo); +} + +#ifndef __UBOOT__ +/** + * pkcs7_verify - Verify a PKCS#7 message + * @pkcs7: The PKCS#7 message to be verified + * @usage: The use to which the key is being put + * + * Verify a PKCS#7 message is internally consistent - that is, the data digest + * matches the digest in the AuthAttrs and any signature in the message or one + * of the X.509 certificates it carries that matches another X.509 cert in the + * message can be verified. + * + * This does not look to match the contents of the PKCS#7 message against any + * external public keys. + * + * Returns, in order of descending priority: + * + * (*) -EKEYREJECTED if a key was selected that had a usage restriction at + * odds with the specified usage, or: + * + * (*) -EKEYREJECTED if a signature failed to match for which we found an + * appropriate X.509 certificate, or: + * + * (*) -EBADMSG if some part of the message was invalid, or: + * + * (*) 0 if a signature chain passed verification, or: + * + * (*) -EKEYREJECTED if a blacklisted key was encountered, or: + * + * (*) -ENOPKG if none of the signature chains are verifiable because suitable + * crypto modules couldn't be found. + */ +int pkcs7_verify(struct pkcs7_message *pkcs7, + enum key_being_used_for usage) +{ + struct pkcs7_signed_info *sinfo; + int actual_ret = -ENOPKG; + int ret; + + kenter(""); + + switch (usage) { + case VERIFYING_MODULE_SIGNATURE: + if (pkcs7->data_type != OID_data) { + pr_warn("Invalid module sig (not pkcs7-data)\n"); + return -EKEYREJECTED; + } + if (pkcs7->have_authattrs) { + pr_warn("Invalid module sig (has authattrs)\n"); + return -EKEYREJECTED; + } + break; + case VERIFYING_FIRMWARE_SIGNATURE: + if (pkcs7->data_type != OID_data) { + pr_warn("Invalid firmware sig (not pkcs7-data)\n"); + return -EKEYREJECTED; + } + if (!pkcs7->have_authattrs) { + pr_warn("Invalid firmware sig (missing authattrs)\n"); + return -EKEYREJECTED; + } + break; + case VERIFYING_KEXEC_PE_SIGNATURE: + if (pkcs7->data_type != OID_msIndirectData) { + pr_warn("Invalid kexec sig (not Authenticode)\n"); + return -EKEYREJECTED; + } + /* Authattr presence checked in parser */ + break; + case VERIFYING_UNSPECIFIED_SIGNATURE: + if (pkcs7->data_type != OID_data) { + pr_warn("Invalid unspecified sig (not pkcs7-data)\n"); + return -EKEYREJECTED; + } + break; + default: + return -EINVAL; + } + + for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { + ret = pkcs7_verify_one(pkcs7, sinfo); + if (sinfo->blacklisted) { + if (actual_ret == -ENOPKG) + actual_ret = -EKEYREJECTED; + continue; + } + if (ret < 0) { + if (ret == -ENOPKG) { + sinfo->unsupported_crypto = true; + continue; + } + kleave(" = %d", ret); + return ret; + } + actual_ret = 0; + } + + kleave(" = %d", actual_ret); + return actual_ret; +} +EXPORT_SYMBOL_GPL(pkcs7_verify); + +/** + * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message + * @pkcs7: The PKCS#7 message + * @data: The data to be verified + * @datalen: The amount of data + * + * Supply the detached data needed to verify a PKCS#7 message. Note that no + * attempt to retain/pin the data is made. That is left to the caller. The + * data will not be modified by pkcs7_verify() and will not be freed when the + * PKCS#7 message is freed. + * + * Returns -EINVAL if data is already supplied in the message, 0 otherwise. + */ +int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7, + const void *data, size_t datalen) +{ + if (pkcs7->data) { + pr_debug("Data already supplied\n"); + return -EINVAL; + } + pkcs7->data = data; + pkcs7->data_len = datalen; + return 0; +} +#endif /* __UBOOT__ */