Fix Null pointer deref in X509_issuer_and_serial_hash()

The OpenSSL public API function X509_issuer_and_serial_hash() attempts to create a unique hash value based on the issuer and serial number data contained within an X509 certificate. However it fails to correctly handle any errors that may occur while parsing the issuer field (which might occur if the issuer field is maliciously constructed). This may subsequently result in a NULL pointer deref and a crash leading to a potential denial of service attack. The function X509_issuer_and_serial_hash() is never directly called by OpenSSL itself so applications are only vulnerable if they use this function directly and they use it on certificates that may have been obtained from untrusted sources. CVE-2021-23841 Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Paul Dale <pauli@openssl.org> (cherry picked from commit 8130d65)
openssl · Feb 16, 2021 · 122a19a · 122a19a · billz1990 · Mar 12, 2021
1 parent c8c6e74
commit 122a19a
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/crypto/x509/x509_cmp.c b/crypto/x509/x509_cmp.c
@@ -39,6 +39,8 @@ unsigned long X509_issuer_and_serial_hash(X509 *a)
     if (ctx == NULL)
         goto err;
     f = X509_NAME_oneline(a->cert_info.issuer, NULL, 0);
+    if (f == NULL)
+        goto err;
     if (!EVP_DigestInit_ex(ctx, EVP_md5(), NULL))
         goto err;
     if (!EVP_DigestUpdate(ctx, (unsigned char *)f, strlen(f)))