Hook into the autoboot flow as an alternative to the existing mechanisms.
Signed-off-by: Steffen Jaeckel jaeckel-floss@eyet-services.de ---
common/Kconfig.boot | 23 +++++++++--- common/autoboot.c | 85 ++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 95 insertions(+), 13 deletions(-)
diff --git a/common/Kconfig.boot b/common/Kconfig.boot index 5a18d62d78..d8012ead3e 100644 --- a/common/Kconfig.boot +++ b/common/Kconfig.boot @@ -812,10 +812,16 @@ config AUTOBOOT_ENCRYPTION depends on AUTOBOOT_KEYED help This option allows a string to be entered into U-Boot to stop the - autoboot. The string itself is hashed and compared against the hash - in the environment variable 'bootstopkeysha256'. If it matches then - boot stops and a command-line prompt is presented. - + autoboot. + The behavior depends whether CONFIG_CRYPT_PW is enabled or not. + In case CONFIG_CRYPT_PW is enabled, the string will be forwarded + to the crypt-based functionality and be compared against the + string in the environment variable 'bootstopkeycrypt'. + In case CONFIG_CRYPT_PW is disabled the string itself is hashed + and compared against the hash in the environment variable + 'bootstopkeysha256'. + If it matches in either case then boot stops and + a command-line prompt is presented. This provides a way to ship a secure production device which can also be accessed at the U-Boot command line.
@@ -853,6 +859,15 @@ config AUTOBOOT_KEYED_CTRLC Setting this variable provides an escape sequence from the limited "password" strings.
+config AUTOBOOT_STOP_STR_CRYPT + string "Stop autobooting via crypt-hashed password" + depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION + help + This option adds the feature to only stop the autobooting, + and therefore boot into the U-Boot prompt, when the input + string / password matches a values that is hashed via + one of support crypt options and saved in the environment. + config AUTOBOOT_STOP_STR_SHA256 string "Stop autobooting via SHA256 encrypted password" depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION diff --git a/common/autoboot.c b/common/autoboot.c index 0bb08e7a4c..de60635d2a 100644 --- a/common/autoboot.c +++ b/common/autoboot.c @@ -23,6 +23,7 @@ #include <linux/delay.h> #include <u-boot/sha256.h> #include <bootcount.h> +#include <crypt.h>
DECLARE_GLOBAL_DATA_PTR;
@@ -38,18 +39,80 @@ DECLARE_GLOBAL_DATA_PTR; static int stored_bootdelay; static int menukey;
-#ifdef CONFIG_AUTOBOOT_ENCRYPTION -#define AUTOBOOT_STOP_STR_SHA256 CONFIG_AUTOBOOT_STOP_STR_SHA256 -#else -#define AUTOBOOT_STOP_STR_SHA256 "" +#if defined(CONFIG_AUTOBOOT_ENCRYPTION) +#if defined(CONFIG_CRYPT_PW) && defined(CONFIG_AUTOBOOT_STOP_STR_CRYPT) +#define AUTOBOOT_STOP_STR_ENC CONFIG_AUTOBOOT_STOP_STR_CRYPT +#define HAS_STOP_STR_CRYPT 1 +#elif defined(CONFIG_AUTOBOOT_STOP_STR_SHA256) +#define AUTOBOOT_STOP_STR_ENC CONFIG_AUTOBOOT_STOP_STR_SHA256 +#endif +#endif +#if !defined(AUTOBOOT_STOP_STR_ENC) +#define AUTOBOOT_STOP_STR_ENC "" #endif - #ifdef CONFIG_USE_AUTOBOOT_MENUKEY #define AUTOBOOT_MENUKEY CONFIG_USE_AUTOBOOT_MENUKEY #else #define AUTOBOOT_MENUKEY 0 #endif
+/** + * passwd_abort_crypt() - check for a crypt-style hashed key sequence to abort booting + * + * This checks for the user entering a password within a given time. + * + * The entered password is hashed via one of the crypt-style hash methods + * and compared to the pre-defined value from either + * the environment variable "bootstopkeycrypt" + * or + * the config value CONFIG_AUTOBOOT_STOP_STR_CRYPT + * + * @etime: Timeout value ticks (stop when get_ticks() reachs this) + * @return 0 if autoboot should continue, 1 if it should stop + */ +static int passwd_abort_crypt(uint64_t etime) +{ + const char *crypt_env_str = env_get("bootstopkeycrypt"); + char presskey[MAX_DELAY_STOP_STR]; + u_int presskey_len = 0; + int abort = 0; + int err; + + if (IS_ENABLED(HAS_STOP_STR_CRYPT) && !crypt_env_str) + crypt_env_str = AUTOBOOT_STOP_STR_ENC; + + if (!crypt_env_str) + return 0; + + /* We expect the stop-string to be newline terminated. */ + do { + if (tstc()) { + /* Check for input string overflow */ + if (presskey_len >= MAX_DELAY_STOP_STR) + return 0; + + presskey[presskey_len] = getchar(); + + if ((presskey[presskey_len] == '\r') || + (presskey[presskey_len] == '\n')) { + presskey[presskey_len] = '\0'; + err = crypt_compare(crypt_env_str, presskey, + &abort); + if (err) + debug_bootkeys( + "crypt_compare() failed with: %s\n", + errno_str(err)); + /* you had one chance */ + break; + } else { + presskey_len++; + } + } + } while (get_ticks() <= etime); + + return abort; +} + /* * Use a "constant-length" time compare function for this * hash compare: @@ -89,7 +152,7 @@ static int passwd_abort_sha256(uint64_t etime) int ret;
if (sha_env_str == NULL) - sha_env_str = AUTOBOOT_STOP_STR_SHA256; + sha_env_str = AUTOBOOT_STOP_STR_ENC;
presskey = malloc_cache_aligned(MAX_DELAY_STOP_STR); c = strstr(sha_env_str, ":"); @@ -245,10 +308,14 @@ static int abortboot_key_sequence(int bootdelay) printf(CONFIG_AUTOBOOT_PROMPT, bootdelay); # endif
- if (IS_ENABLED(CONFIG_AUTOBOOT_ENCRYPTION)) - abort = passwd_abort_sha256(etime); - else + if (IS_ENABLED(CONFIG_AUTOBOOT_ENCRYPTION)) { + if (IS_ENABLED(CONFIG_CRYPT_PW)) + abort = passwd_abort_crypt(etime); + else + abort = passwd_abort_sha256(etime); + } else { abort = passwd_abort_key(etime); + } if (!abort) debug_bootkeys("key timeout\n");