Various X509 fixes. Disable broken certificate workarounds

when X509_V_FLAG_X509_STRICT is set. Check for CRLSign in
CRL issuer certificates. Reject CRLs with unhandled (any)
critical extensions.

CHANGES

@@ -617,6 +617,14 @@
 
  Changes between 0.9.7c and 0.9.7d  [xx XXX XXXX]
 
+  *) X509 verify fixes. Disable broken certificate workarounds when 
+     X509_V_FLAGS_X509_STRICT is set. Check CRL issuer has cRLSign set if
+     keyUsage extension present. Don't accept CRLs with unhandled critical
+     extensions: since verify currently doesn't process CRL extensions this
+     rejects a CRL with *any* critical extensions. Add new verify error codes
+     for these cases.
+     [Steve Henson]
+
   *) When creating an OCSP nonce use an OCTET STRING inside the extnValue.
      A clarification of RFC2560 will require the use of OCTET STRINGs and 
      some implementations cannot handle the current raw format. Since OpenSSL

crypto/x509/x509_txt.c

@@ -147,6 +147,12 @@ const char *X509_verify_cert_error_string(long n)
 	case X509_V_ERR_UNHANDLED_CRITICAL_EXTENSION:
 		return("unhandled critical extension");
 
+	case X509_V_ERR_KEYUSAGE_NO_CRL_SIGN:
+		return("key usage does not include CRL signing");
+
+	case X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION:
+		return("unhandled critical CRL extension");
+
 	default:
 		BIO_snprintf(buf,sizeof buf,"error number %ld",n);
 		return(buf);

crypto/x509/x509_vfy.c

@@ -383,6 +383,7 @@ static int check_chain_purpose(X509_STORE_CTX *ctx)
 	/* Check all untrusted certificates */
 	for (i = 0; i < ctx->last_untrusted; i++)
 		{
+		int ret;
 		x = sk_X509_value(ctx->chain, i);
 		if (!(ctx->flags & X509_V_FLAG_IGNORE_CRITICAL)
 			&& (x->ex_flags & EXFLAG_CRITICAL))
@@ -393,7 +394,10 @@ static int check_chain_purpose(X509_STORE_CTX *ctx)
 			ok=cb(0,ctx);
 			if (!ok) goto end;
 			}
-		if (!X509_check_purpose(x, ctx->purpose, i))
+		ret = X509_check_purpose(x, ctx->purpose, i);
+		if ((ret == 0)
+			 || ((ctx->flags & X509_V_FLAG_X509_STRICT)
+				&& (ret != 1)))
 			{
 			if (i)
 				ctx->error = X509_V_ERR_INVALID_CA;
@@ -537,6 +541,14 @@ static int check_crl(X509_STORE_CTX *ctx, X509_CRL *crl)
 
 	if(issuer)
 		{
+		/* Check for cRLSign bit if keyUsage present */
+		if ((issuer->ex_flags & EXFLAG_KUSAGE) &&
+			!(issuer->ex_kusage & KU_CRL_SIGN))
+			{
+			ctx->error = X509_V_ERR_KEYUSAGE_NO_CRL_SIGN;
+			ok = ctx->verify_cb(0, ctx);
+			if(!ok) goto err;
+			}
 
 		/* Attempt to get issuer certificate public key */
 		ikey = X509_get_pubkey(issuer);
@@ -611,17 +623,46 @@ static int cert_crl(X509_STORE_CTX *ctx, X509_CRL *crl, X509 *x)
 	{
 	int idx, ok;
 	X509_REVOKED rtmp;
+	STACK_OF(X509_EXTENSION) *exts;
+	X509_EXTENSION *ext;
 	/* Look for serial number of certificate in CRL */
 	rtmp.serialNumber = X509_get_serialNumber(x);
 	idx = sk_X509_REVOKED_find(crl->crl->revoked, &rtmp);
-	/* Not found: OK */
+	/* If found assume revoked: want something cleverer than
-	if(idx == -1) return 1;
-	/* Otherwise revoked: want something cleverer than
 	 * this to handle entry extensions in V2 CRLs.
 	 */
+	if(idx >= 0)
+		{
 		ctx->error = X509_V_ERR_CERT_REVOKED;
 		ok = ctx->verify_cb(0, ctx);
-	return ok;
+		if (!ok) return 0;
+		}
+
+	if (ctx->flags & X509_V_FLAG_IGNORE_CRITICAL)
+		return 1;
+
+	/* See if we have any critical CRL extensions: since we
+	 * currently don't handle any CRL extensions the CRL must be
+	 * rejected. 
+	 * This code accesses the X509_CRL structure directly: applications
+	 * shouldn't do this.
+	 */
+
+	exts = crl->crl->extensions;
+
+	for (idx = 0; idx < sk_X509_EXTENSION_num(exts); idx++)
+		{
+		ext = sk_X509_EXTENSION_value(exts, idx);
+		if (ext->critical > 0)
+			{
+			ctx->error =
+				X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION;
+			ok = ctx->verify_cb(0, ctx);
+			if(!ok) return 0;
+			break;
+			}
+		}
+	return 1;
 	}
 
 static int internal_verify(X509_STORE_CTX *ctx)

crypto/x509/x509_vfy.h

@@ -305,17 +305,26 @@ struct x509_store_ctx_st      /* X509_STORE_CTX */
 
 #define		X509_V_ERR_UNABLE_TO_GET_CRL_ISSUER		33
 #define		X509_V_ERR_UNHANDLED_CRITICAL_EXTENSION		34
+#define		X509_V_ERR_KEYUSAGE_NO_CRL_SIGN			35
+#define		X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION	36
 
 /* The application is not happy */
 #define		X509_V_ERR_APPLICATION_VERIFICATION		50
 
 /* Certificate verify flags */
 
-#define	X509_V_FLAG_CB_ISSUER_CHECK		0x1	/* Send issuer+subject checks to verify_cb */
+/* Send issuer+subject checks to verify_cb */
-#define	X509_V_FLAG_USE_CHECK_TIME		0x2	/* Use check time instead of current time */
+#define	X509_V_FLAG_CB_ISSUER_CHECK		0x1
-#define	X509_V_FLAG_CRL_CHECK			0x4	/* Lookup CRLs */
+/* Use check time instead of current time */
-#define	X509_V_FLAG_CRL_CHECK_ALL		0x8	/* Lookup CRLs for whole chain */
+#define	X509_V_FLAG_USE_CHECK_TIME		0x2
-#define	X509_V_FLAG_IGNORE_CRITICAL		0x10	/* Ignore unhandled critical extensions */
+/* Lookup CRLs */
+#define	X509_V_FLAG_CRL_CHECK			0x4
+/* Lookup CRLs for whole chain */
+#define	X509_V_FLAG_CRL_CHECK_ALL		0x8
+/* Ignore unhandled critical extensions */
+#define	X509_V_FLAG_IGNORE_CRITICAL		0x10
+/* Disable workarounds for broken certificates */
+#define	X509_V_FLAG_X509_STRICT			0x20
 
 int X509_OBJECT_idx_by_subject(STACK_OF(X509_OBJECT) *h, int type,
 	     X509_NAME *name);

crypto/x509v3/v3_purp.c

@@ -3,7 +3,7 @@
  * project 2001.
  */
 /* ====================================================================
- * Copyright (c) 1999-2001 The OpenSSL Project.  All rights reserved.
+ * Copyright (c) 1999-2004 The OpenSSL Project.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -415,6 +415,7 @@ static void x509v3_cache_extensions(X509 *x)
  * 1 is a CA
  * 2 basicConstraints absent so "maybe" a CA
  * 3 basicConstraints absent but self signed V1.
+ * 4 basicConstraints absent but keyUsage present and keyCertSign asserted.
  */
 
 #define V1_ROOT (EXFLAG_V1|EXFLAG_SS)
@@ -436,7 +437,7 @@ static int ca_check(const X509 *x)
 	} else {
 		if((x->ex_flags & V1_ROOT) == V1_ROOT) return 3;
 		/* If key usage present it must have certSign so tolerate it */
-		else if (x->ex_flags & EXFLAG_KUSAGE) return 3;
+		else if (x->ex_flags & EXFLAG_KUSAGE) return 4;
 		else return 2;
 	}
 }