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lib: rsa: Update function padding_pss_verify (any-salt)

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Modify function to support any salt length instead of max
length only. Function now detects salt length by parsing
the content of db buffer. Note that it works with (but is
not limited to) zero-length, digest-length and max-length

Signed-off-by: SESA644425 <gioja.hermann@non.se.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
SESA644425 2022-03-09 01:27:17 -08:00 • committed by Tom Rini
parent fb7330545e
commit 81eff51047
1 changed files with 11 additions and 8 deletions
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19
lib/rsa/rsa-verify.c
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@ -204,9 +204,7 @@ out:
/* /*
* padding_pss_verify() - verify the pss padding of a signature * padding_pss_verify() - verify the pss padding of a signature
* *
* Only works with a rsa_pss_saltlen:-2 (default value) right now * Works with any salt length
* saltlen:-1 "set the salt length to the digest length" is currently
* not supported.
* *
* msg is a concatenation of : masked_db + h + 0xbc * msg is a concatenation of : masked_db + h + 0xbc
* Once unmasked, db is a concatenation of : [0x00]* + 0x01 + salt * Once unmasked, db is a concatenation of : [0x00]* + 0x01 + salt
@ -229,8 +227,8 @@ int padding_pss_verify(struct image_sign_info *info,
const uint8_t *h = NULL; const uint8_t *h = NULL;
uint8_t *hprime = NULL; uint8_t *hprime = NULL;
int h_len = hash_len; int h_len = hash_len;
uint8_t *salt = NULL; uint8_t *db_nopad = NULL, *salt = NULL;
int salt_len = msg_len - hash_len - 2; int db_padlen, salt_len;
uint8_t pad_zero[8] = { 0 }; uint8_t pad_zero[8] = { 0 };
int ret, i, leftmost_bits = 1; int ret, i, leftmost_bits = 1;
uint8_t leftmost_mask; uint8_t leftmost_mask;
@ -277,15 +275,20 @@ int padding_pss_verify(struct image_sign_info *info,
db[0] &= 0xff >> leftmost_bits; db[0] &= 0xff >> leftmost_bits;
/* step 10 */ /* step 10 */
if (db[0] != 0x01) { db_padlen = 0;
while (db[db_padlen] == 0x00 && db_padlen < (db_len - 1))
db_padlen++;
db_nopad = &db[db_padlen];
if (db_nopad[0] != 0x01) {
printf("%s: invalid pss padding ", __func__); printf("%s: invalid pss padding ", __func__);
printf("(leftmost byte of db isn't 0x01)\n"); printf("(leftmost byte of db after 0-padding isn't 0x01)\n");
ret = EINVAL; ret = EINVAL;
goto out; goto out;
} }
/* step 11 */ /* step 11 */
salt = &db[1]; salt_len = db_len - db_padlen - 1;
salt = &db_nopad[1];
/* step 12 & 13 */ /* step 12 & 13 */
compute_hash_prime(checksum, pad_zero, 8, compute_hash_prime(checksum, pad_zero, 8,