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Fix slh-dsa fuzzer on invalid param inputs

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oss-fuzz issue:
https://issues.oss-fuzz.com/issues/397734693

Fails because the fuzzer occasionaly provides inputs which drives the
fuzzer to create an octet-string for the context_string param which
violates the 255 byte constraint documented on that parameter.

Fix it by detecting that condition, expecting failure in the call to
EVP_sign_message_init, and bailing out when it occurs.

Fixes openssl/project#1109

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/26851)
This commit is contained in:
Neil Horman 2025-02-20 07:45:50 -05:00
parent 17d2fd0752
commit 3be71de4d9
1 changed files with 16 additions and 1 deletions
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17
fuzz/slh-dsa.c
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@ -319,6 +319,7 @@ static void slh_dsa_sign_verify(uint8_t **buf, size_t *len, void *key1,
OSSL_PARAM params[4];
int paramidx = 0;
int intval;
int expect_init_rc = 1;
*buf = consume_uint8t(*buf, len, &selector);
if (*buf == NULL)
@ -338,6 +339,11 @@ static void slh_dsa_sign_verify(uint8_t **buf, size_t *len, void *key1,
*/
msg = (unsigned char *)*buf;
msg_len = *len;
/* if msg_len > 255, sign_message_init will fail */
if (msg_len > 255)
expect_init_rc = 0;
*len = 0;
if (selector & 0x1)
@ -368,7 +374,15 @@ static void slh_dsa_sign_verify(uint8_t **buf, size_t *len, void *key1,
sig_alg = EVP_SIGNATURE_fetch(NULL, keytype, NULL);
OPENSSL_assert(sig_alg != NULL);
OPENSSL_assert(EVP_PKEY_sign_message_init(ctx, sig_alg, params));
OPENSSL_assert(EVP_PKEY_sign_message_init(ctx, sig_alg, params) == expect_init_rc);
/*
* the context_string parameter can be no more than 255 bytes, so if
* our random input buffer is greater than that, we expect failure above,
* which we check for. In that event, theres nothing more we can do here
* so bail out
*/
if (expect_init_rc == 0)
goto out;
OPENSSL_assert(EVP_PKEY_sign(ctx, NULL, &sig_len, msg, msg_len));
sig = OPENSSL_zalloc(sig_len);
@ -379,6 +393,7 @@ static void slh_dsa_sign_verify(uint8_t **buf, size_t *len, void *key1,
OPENSSL_assert(EVP_PKEY_verify_message_init(ctx, sig_alg, params));
OPENSSL_assert(EVP_PKEY_verify(ctx, sig, sig_len, msg, msg_len));
out:
OPENSSL_free(sig);
EVP_SIGNATURE_free(sig_alg);
EVP_PKEY_CTX_free(ctx);