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CVE-2023-2283:pki_crypto: Fix possible authentication bypass

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The return value is changed by the call to pki_key_check_hash_compatible
causing the possibility of returning SSH_OK if memory allocation error
happens later in the function.

The assignment of SSH_ERROR if the verification fails is no longer needed,
because the value of the variable is already SSH_ERROR.

Signed-off-by: Norbert Pocs <npocs@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Norbert Pocs
2023-04-24 11:51:36 +02:00
committed by Andreas Schneider
parent 4e8db9d44b
commit 0bda152ad2
1 changed files with 15 additions and 11 deletions
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26
src/pki_crypto.c
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@@ -2229,8 +2229,12 @@ int pki_verify_data_signature(ssh_signature signature,
unsigned char *raw_sig_data = NULL; unsigned char *raw_sig_data = NULL;
unsigned int raw_sig_len; unsigned int raw_sig_len;
/* Function return code
* Do not change this variable throughout the function until the signature
* is successfully verified!
*/
int rc = SSH_ERROR; int rc = SSH_ERROR;
int evp_rc; int ok;
if (pubkey == NULL || ssh_key_is_private(pubkey) || input == NULL || if (pubkey == NULL || ssh_key_is_private(pubkey) || input == NULL ||
signature == NULL || signature->raw_sig == NULL) signature == NULL || signature->raw_sig == NULL)
@@ -2241,8 +2245,8 @@ int pki_verify_data_signature(ssh_signature signature,
} }
/* Check if public key and hash type are compatible */ /* Check if public key and hash type are compatible */
rc = pki_key_check_hash_compatible(pubkey, signature->hash_type); ok = pki_key_check_hash_compatible(pubkey, signature->hash_type);
if (rc != SSH_OK) { if (ok != SSH_OK) {
return SSH_ERROR; return SSH_ERROR;
} }
@@ -2277,25 +2281,25 @@ int pki_verify_data_signature(ssh_signature signature,
} }
/* Verify the signature */ /* Verify the signature */
evp_rc = EVP_DigestVerifyInit(ctx, NULL, md, NULL, pkey); ok = EVP_DigestVerifyInit(ctx, NULL, md, NULL, pkey);
if (evp_rc != 1){ if (ok != 1){
SSH_LOG(SSH_LOG_TRACE, SSH_LOG(SSH_LOG_TRACE,
"EVP_DigestVerifyInit() failed: %s", "EVP_DigestVerifyInit() failed: %s",
ERR_error_string(ERR_get_error(), NULL)); ERR_error_string(ERR_get_error(), NULL));
goto out; goto out;
} }
evp_rc = EVP_DigestVerify(ctx, raw_sig_data, raw_sig_len, input, input_len); ok = EVP_DigestVerify(ctx, raw_sig_data, raw_sig_len, input, input_len);
if (evp_rc == 1) { if (ok != 1) {
SSH_LOG(SSH_LOG_TRACE, "Signature valid");
rc = SSH_OK;
} else {
SSH_LOG(SSH_LOG_TRACE, SSH_LOG(SSH_LOG_TRACE,
"Signature invalid: %s", "Signature invalid: %s",
ERR_error_string(ERR_get_error(), NULL)); ERR_error_string(ERR_get_error(), NULL));
rc = SSH_ERROR; goto out;
} }
SSH_LOG(SSH_LOG_TRACE, "Signature valid");
rc = SSH_OK;
out: out:
if (ctx != NULL) { if (ctx != NULL) {
EVP_MD_CTX_free(ctx); EVP_MD_CTX_free(ctx);