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common: add support to fallback to plain SHA256

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In case crypt-based hashing is enabled this will be the default mechanism
that is used. If a user wants to have support for both, the environment
variable `bootstopusesha256` can be set to `true` to allow plain SHA256
based hashing of the password.

Signed-off-by: Steffen Jaeckel <jaeckel-floss@eyet-services.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Steffen Jaeckel 2021-07-08 15:57:39 +02:00 committed by Tom Rini
parent d199c3ab1c
commit 33198740ac
2 changed files with 29 additions and 1 deletions
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8
common/Kconfig.boot
View File

@ -835,6 +835,14 @@ config AUTOBOOT_ENCRYPTION
This provides a way to ship a secure production device which can also
be accessed at the U-Boot command line.
config AUTOBOOT_SHA256_FALLBACK
bool "Allow fallback from crypt-hashed password to sha256"
depends on AUTOBOOT_ENCRYPTION && CRYPT_PW
help
This option adds support to fall back from crypt-hashed
passwords to checking a SHA256 hashed password in case the
'bootstopusesha256' environment variable is set to 'true'.
config AUTOBOOT_DELAY_STR
string "Delay autobooting via specific input key / string"
depends on AUTOBOOT_KEYED && !AUTOBOOT_ENCRYPTION

22
common/autoboot.c
View File

@ -306,6 +306,26 @@ static void flush_stdin(void)
(void)getchar();
}
/**
* fallback_to_sha256() - check whether we should fall back to sha256
* password checking
*
* This checks for the environment variable `bootstopusesha256` in case
* sha256-fallback has been enabled via the config setting
* `AUTOBOOT_SHA256_FALLBACK`.
*
* @return `false` if we must not fall-back, `true` if plain sha256 should be tried
*/
static bool fallback_to_sha256(void)
{
if (IS_ENABLED(CONFIG_AUTOBOOT_SHA256_FALLBACK))
return env_get_yesno("bootstopusesha256") == 1;
else if (IS_ENABLED(CONFIG_CRYPT_PW))
return false;
else
return true;
}
/***************************************************************************
* Watch for 'delay' seconds for autoboot stop or autoboot delay string.
* returns: 0 - no key string, allow autoboot 1 - got key string, abort
@ -326,7 +346,7 @@ static int abortboot_key_sequence(int bootdelay)
# endif
if (IS_ENABLED(CONFIG_AUTOBOOT_ENCRYPTION)) {
if (IS_ENABLED(CONFIG_CRYPT_PW))
if (IS_ENABLED(CONFIG_CRYPT_PW) && !fallback_to_sha256())
abort = passwd_abort_crypt(etime);
else
abort = passwd_abort_sha256(etime);