Modify verify code to handle self signed certificates.

CHANGES

@@ -4,6 +4,19 @@
 
  Changes between 0.9.4 and 0.9.5  [xx XXX 1999]
 
+  *) First update to verify code. Change the verify utility
+     so it warns if it is passed a self signed certificate:
+     for consistency with the normal behaviour. X509_verify
+     has been modified to it will now verify a self signed
+     certificate if *exactly* the same certificate appears
+     in the store: it was previously impossible to trust a
+     single self signed certificate. This means that:
+     openssl verify ss.pem
+     now gives a warning about a self signed certificate but
+     openssl verify -CAfile ss.pem ss.pem
+     is OK.
+     [Steve Henson]
+
   *) For servers, store verify_result in SSL_SESSION data structure
      (and add it to external session representation).
      This is needed when client certificate verifications fails,
@@ -18,7 +31,7 @@
   *) Fix a bug in the new PKCS#7 code: it didn't consider the
      case in PKCS7_dataInit() where the signed PKCS7 structure
      didn't contain any existing data because it was being created.
-     [Po-Cheng Chen" <pocheng@nst.com.tw>, slightly modified by Steve Henson]
+     [Po-Cheng Chen <pocheng@nst.com.tw>, slightly modified by Steve Henson]
 
   *) Add a salt to the key derivation routines in enc.c. This
      forms the first 8 bytes of the encrypted file. Also add a

apps/verify.c

@@ -206,21 +206,18 @@ static int MS_CALLBACK cb(int ok, X509_STORE_CTX *ctx)
 
 	if (!ok)
 		{
-		/* since we are just checking the certificates, it is
-		 * ok if they are self signed. */
-		if (ctx->error == X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT)
-			ok=1;
-		else
-			{
-			X509_NAME_oneline(
+		X509_NAME_oneline(
 				X509_get_subject_name(ctx->current_cert),buf,256);
-			printf("%s\n",buf);
-			printf("error %d at %d depth lookup:%s\n",ctx->error,
-				ctx->error_depth,
-				X509_verify_cert_error_string(ctx->error));
-			if (ctx->error == X509_V_ERR_CERT_HAS_EXPIRED)
-				ok=1;
-			}
+		printf("%s\n",buf);
+		printf("error %d at %d depth lookup:%s\n",ctx->error,
+			ctx->error_depth,
+			X509_verify_cert_error_string(ctx->error));
+		if (ctx->error == X509_V_ERR_CERT_HAS_EXPIRED) ok=1;
+		/* since we are just checking the certificates, it is
+		 * ok if they are self signed. But we should still warn
+		 * the user.
+ 		 */
+		if (ctx->error == X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT) ok=1;
 		}
 	if (!v_verbose)
 		ERR_clear_error();

crypto/x509/x509_vfy.c

@@ -125,7 +125,7 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
 		ctx->last_untrusted=1;
 		}
 
-	/* We use a temporary so we can chop and hack at it */
+	/* We use a temporary STACK so we can chop and hack at it */
 	if (ctx->untrusted != NULL
 	    && (sktmp=sk_X509_dup(ctx->untrusted)) == NULL)
 		{
@@ -182,17 +182,37 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
 
 	i=sk_X509_num(ctx->chain);
 	x=sk_X509_value(ctx->chain,i-1);
-	if (X509_NAME_cmp(X509_get_subject_name(x),X509_get_issuer_name(x))
+	xn = X509_get_subject_name(x);
+	if (X509_NAME_cmp(xn,X509_get_issuer_name(x))
 		== 0)
 		{
 		/* we have a self signed certificate */
 		if (sk_X509_num(ctx->chain) == 1)
 			{
-			ctx->error=X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT;
-			ctx->current_cert=x;
-			ctx->error_depth=i-1;
-			ok=cb(0,ctx);
-			if (!ok) goto end;
+			/* We have a single self signed certificate: see if
+			 * we can find it in the store. We must have an exact
+			 * match to avoid possible impersonation.
+			 */
+			ok=X509_STORE_get_by_subject(ctx,X509_LU_X509,xn,&obj);
+			if ((ok != X509_LU_X509) || X509_cmp(x, obj.data.x509)) 
+				{
+				ctx->error=X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT;
+				ctx->current_cert=x;
+				ctx->error_depth=i-1;
+				if(ok == X509_LU_X509) X509_OBJECT_free_contents(&obj);
+				ok=cb(0,ctx);
+				if (!ok) goto end;
+				}
+			else 
+				{
+				/* We have a match: replace certificate with store version
+				 * so we get any trust settings.
+				 */
+				X509_free(x);
+				x = obj.data.x509;
+				sk_X509_set(ctx->chain, i - 1, x);
+				ctx->last_untrusted=0;
+				}
 			}
 		else
 			{