On 11/20/20 2:41 AM, Joel Peshkin wrote:
From: Joel Peshkin <joel.pesh...@broadcom.com>
Adds an optional SALT value to AUTOBOOT_STOP_STR_SHA256. If a string
followed by a ":" is prepended to the sha256, the portion to the left
of the colon will be used as a salt and the password will be appended
to the salt before the sha256 is computed and compared.
Signed-off-by: Joel Peshkin <joel.pesh...@broadcom.com>
---
common/Kconfig.boot | 5 ++++-
common/autoboot.c | 10 +++++++++-
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/common/Kconfig.boot b/common/Kconfig.boot
index 3f6d9c1..8a98672 100644
--- a/common/Kconfig.boot
+++ b/common/Kconfig.boot
@@ -819,7 +819,10 @@ config AUTOBOOT_STOP_STR_SHA256
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 encypted via
- a SHA256 hash and saved in the environment.
+ a SHA256 hash and saved in the environment variable
+ "bootstopkeysha256". If the value in that variable
+ includes a ":", the portion prior to the ":" will be treated
+ as a salt value.
config AUTOBOOT_USE_MENUKEY
bool "Allow a specify key to run a menu from the environment"
diff --git a/common/autoboot.c b/common/autoboot.c
index e628baf..0c4e6ff 100644
--- a/common/autoboot.c
+++ b/common/autoboot.c
@@ -80,6 +80,7 @@ static int passwd_abort_sha256(uint64_t etime)
u8 sha_env[SHA256_SUM_LEN];
u8 *sha;
char *presskey;
+ char *c;
const char *algo_name = "sha256";
u_int presskey_len = 0;
int abort = 0;
@@ -89,6 +90,14 @@ static int passwd_abort_sha256(uint64_t etime)
if (sha_env_str == NULL)
sha_env_str = AUTOBOOT_STOP_STR_SHA256;
+ presskey = malloc_cache_aligned(MAX_DELAY_STOP_STR);
+ c = strstr(sha_env_str, ":");
+ if (c) {
+ /* preload presskey with salt */
+ memcpy(presskey, sha_env_str, c - sha_env_str);
Dear Joel,
thank you for your contribution helping to fend of password attacks
using lookup-tables for hashes.
Please, safeguard against
c - sha_env_str > MAX_DELAY_STOP_STR
to avoid a possible buffer overflow.
We have
#define MAX_DELAY_STOP_STR 32
Shouldn't this value be enlarged to encompass a salt with 256 bits of
randomness (matching the SHA256 algorithm)? If you encode 6 bits of
entropy in each character, you need 43 characters for the salt and 43
characters for the password.
+ presskey_len += c - sha_env_str;
This would be more readable:
presskey_len = c - sha_env_str;
Best regards
Heinrich
+ sha_env_str = c + 1;
+ }
/*
* Generate the binary value from the environment hash value
* so that we can compare this value with the computed hash
@@ -100,7 +109,6 @@ static int passwd_abort_sha256(uint64_t etime)
return 0;
}
- presskey = malloc_cache_aligned(MAX_DELAY_STOP_STR);
sha = malloc_cache_aligned(SHA256_SUM_LEN);
size = SHA256_SUM_LEN;
/*
