From: Alexander Chernyakhovsky <achernya@google.com>

Date: Thu, 25 Jul 2013 21:35:14 -0400
Subject: [PATCH 1/3] Implement subject-alt-name and wildcard certificates

src/crypto/x509.c

@@ -520,6 +520,54 @@ static int x509_parse_key_usage ( struct x509_certificate *cert,
 	return 0;
 }
 
+/**
+ * Parse X.509 certificate subject alternative name
+ *
+ * @v cert		X.509 certificate
+ * @v raw		ASN.1 cursor
+ * @ret rc		Return status code
+ */
+static int x509_parse_subject_alt_name ( struct x509_certificate *cert,
+					 const struct asn1_cursor *raw ) {
+	struct x509_subject_alt_name *subject_alt_name = &cert->extensions.subject_alt_name;
+	struct asn1_cursor cursor;
+	struct asn1_cursor string_cursor;
+	int rc;
+
+	/* Mark extension as present */
+	subject_alt_name->present = 1;
+
+	DBGC ( cert, "X509 %p parsing subjectAltName\n", cert );
+
+	/* Enter GeneralNames */
+	memcpy ( &cursor, raw, sizeof ( cursor ) );
+	asn1_enter ( &cursor, ASN1_SEQUENCE );
+	DBGC_HDA ( cert, 0, cursor.data, 128 );
+
+	INIT_LIST_HEAD ( &subject_alt_name->names );
+
+	/* Parse each name in turn */
+	while ( cursor.len ) {
+		memcpy ( &string_cursor, &cursor, sizeof ( string_cursor ) );
+		if ( ( rc = asn1_enter ( &string_cursor, ASN1_IMPLICIT_TAG ( 2 ) ) ) == 0 ) {
+			char* name = zalloc ( string_cursor.len + 1 );
+			memcpy ( name, string_cursor.data, string_cursor.len );
+			if ( strlen ( name ) != string_cursor.len ) {
+				DBGC ( cert, "X509 %p contains malicious subjectAltName\n",
+ 				       cert );
+				return rc;
+			}
+			//DBGC ( cert, "X509 %p subjectAltName %s\n", cert, name );
+			struct x509_san_link* link = zalloc ( sizeof ( struct x509_san_link ) );
+			link->name = name;
+			list_add ( &link->list, &subject_alt_name->names );
+		}
+		asn1_skip_any ( &cursor );
+	}
+
+	return 0;
+}
+
 /** "id-kp-codeSigning" object identifier */
 static uint8_t oid_code_signing[] = { ASN1_OID_CODESIGNING };
 
@@ -738,6 +786,10 @@ static uint8_t oid_ce_basic_constraints[] =
 static uint8_t oid_ce_key_usage[] =
 	{ ASN1_OID_KEYUSAGE };
 
+/** "id-ce-keyUsage" object identifier */
+static uint8_t oid_ce_subject_alt_name[] =
+	{ ASN1_OID_SUBJECTALTNAME };
+
 /** "id-ce-extKeyUsage" object identifier */
 static uint8_t oid_ce_ext_key_usage[] =
 	{ ASN1_OID_EXTKEYUSAGE };
@@ -758,6 +810,11 @@ static struct x509_extension x509_extensions[] = {
 		.oid = ASN1_OID_CURSOR ( oid_ce_key_usage ),
 		.parse = x509_parse_key_usage,
 	},
+	{
+		.name = "subjectAltName",
+		.oid = ASN1_OID_CURSOR ( oid_ce_subject_alt_name ),
+		.parse = x509_parse_subject_alt_name,
+	},
 	{
 		.name = "extKeyUsage",
 		.oid = ASN1_OID_CURSOR ( oid_ce_ext_key_usage ),

src/include/ipxe/asn1.h

@@ -170,6 +170,11 @@ struct asn1_builder_header {
 	ASN1_OID_INITIAL ( 2, 5 ), ASN1_OID_SINGLE ( 29 ),	\
 	ASN1_OID_SINGLE ( 15 )
 
+/** ASN1. OID for id-ce-subjectAltname (2.5.29.17) */
+#define ASN1_OID_SUBJECTALTNAME					\
+	ASN1_OID_INITIAL ( 2, 5 ), ASN1_OID_SINGLE ( 29 ),	\
+	ASN1_OID_SINGLE ( 17 )
+
 /** ASN.1 OID for id-ce-basicConstraints (2.5.29.19) */
 #define ASN1_OID_BASICCONSTRAINTS				\
 	ASN1_OID_INITIAL ( 2, 5 ), ASN1_OID_SINGLE ( 29 ),	\

src/include/ipxe/x509.h

@@ -86,6 +86,21 @@ struct x509_basic_constraints {
 	unsigned int path_len;
 };
 
+/** A link in an X.509 certificate chain */
+struct x509_san_link {
+	/** List of links */
+	struct list_head list;
+	/** name */
+	char* name;
+};
+
+struct x509_subject_alt_name {
+	/** Subject Alternative Name extension is present */
+	int present;
+	/** General Name **/
+	struct list_head names;
+};
+
 /** Unlimited path length
  *
  * We use -2U, since this quantity represents one *fewer* than the
@@ -150,6 +165,8 @@ struct x509_extensions {
 	struct x509_basic_constraints basic;
 	/** Key usage */
 	struct x509_key_usage usage;
+	/** Subject Alternative Name */
+	struct x509_subject_alt_name subject_alt_name;
 	/** Extended key usage */
 	struct x509_extended_key_usage ext_usage;
 	/** Authority information access */

src/net/tls.c

@@ -2427,6 +2427,37 @@ static struct interface_descriptor tls_cipherstream_desc =
  ******************************************************************************
  */
 
+static int dns_wildcard_matcher( const char* dns, const char* wildcard ) {
+	if ( strchr ( wildcard, '*' ) == NULL ) {
+		/* No wildcard, just strcmp */
+		return strcmp ( dns, wildcard );
+	}
+	if ( strrchr(wildcard, '*') != wildcard ) {
+		/* This is multiple-wildcard. We can't handle that, so bail. */
+		return -1;
+	}
+	const char* first_dot = strchr (dns, '*') ;
+	return strcmp ( first_dot, wildcard + 1 );
+}
+
+static int tls_validator_name( struct tls_session *tls, struct x509_certificate *cert ) {
+	/* Verify server name */
+	if ( ( cert->subject.name == NULL ) && ( !cert->extensions.subject_alt_name.present ) ) {
+		return -1;
+	}
+	struct x509_san_link* link;
+	list_for_each_entry ( link, &cert->extensions.subject_alt_name.names, list ) {
+		/* If the name matches, return 0, otherwise, continue */
+		if ( dns_wildcard_matcher ( tls->name, link->name ) == 0) {
+			return 0;
+		}
+	}
+	if ( !cert->extensions.subject_alt_name.present ) {
+		return dns_wildcard_matcher ( tls->name, cert->subject.name );
+	}
+	return -1;
+}
+
 /**
  * Handle certificate validation completion
  *
@@ -2444,7 +2475,7 @@ static void tls_validator_done ( struct tls_session *tls, int rc ) {
 	/* Check for validation failure */
 	if ( rc != 0 ) {
 		DBGC ( tls, "TLS %p certificate validation failed: %s\n",
-		       tls, strerror ( rc ) );
+			     tls, strerror ( rc ) );
 		goto err;
 	}
 	DBGC ( tls, "TLS %p certificate validation succeeded\n", tls );
@@ -2454,8 +2485,7 @@ static void tls_validator_done ( struct tls_session *tls, int rc ) {
 	assert ( cert != NULL );
 
 	/* Verify server name */
-	if ( ( cert->subject.name == NULL ) ||
-	     ( strcmp ( cert->subject.name, tls->name ) != 0 ) ) {
+	if ( tls_validator_name( tls, cert ) ) {
 		DBGC ( tls, "TLS %p server name incorrect (expected %s, got "
 		       "%s)\n", tls, tls->name, cert->subject.name );
 		rc = -EACCES_WRONG_NAME;