[crypto] Remove dynamically-allocated storage for certificate name

iPXE currently allocates a copy the certificate's common name as a
string.  This string is used by the TLS and CMS code to check
certificate names against an expected name, and also appears in
debugging messages.

Provide a function x509_check_name() to centralise certificate name
checking (in preparation for adding subjectAlternativeName support),
and a function x509_name() to provide a name to be used in debugging
messages, and remove the dynamically allocated string.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

6 files changed, 143 insertions, 108 deletions

diff --git a/src/crypto/cms.c b/src/crypto/cms.c
index c0c8d144..6191d1bb 100644
--- a/src/crypto/cms.c
+++ b/src/crypto/cms.c
@@ -130,7 +130,7 @@ static int cms_parse_certificates ( struct cms_signature *sig,
 		}
 		cert = x509_last ( sig->certificates );
 		DBGC ( sig, "CMS %p found certificate %s\n",
-		       sig, cert->subject.name );
+		       sig, x509_name ( cert ) );
 
 		/* Move to next certificate */
 		asn1_skip_any ( &cursor );
@@ -680,8 +680,7 @@ int cms_verify ( struct cms_signature *sig, userptr_t data, size_t len,
 	/* Verify using all signerInfos */
 	list_for_each_entry ( info, &sig->info, list ) {
 		cert = x509_first ( info->chain );
-		if ( name && ( ( cert->subject.name == NULL ) ||
-			       ( strcmp ( cert->subject.name, name ) != 0 ) ) )
+		if ( name && ( x509_check_name ( cert, name ) != 0 ) )
 			continue;
 		if ( ( rc = cms_verify_signer_info ( sig, info, data, len,
 						     time, root ) ) != 0 )
diff --git a/src/crypto/ocsp.c b/src/crypto/ocsp.c
index 27c0080c..1b39fd0d 100644
--- a/src/crypto/ocsp.c
+++ b/src/crypto/ocsp.c
@@ -177,11 +177,11 @@ static int ocsp_request ( struct ocsp_check *ocsp ) {
 		      asn1_wrap ( builder, ASN1_SEQUENCE ),
 		      asn1_wrap ( builder, ASN1_SEQUENCE ) ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" could not build request: %s\n",
-		       ocsp, ocsp->cert->subject.name, strerror ( rc ) );
+		       ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 		return rc;
 	}
 	DBGC2 ( ocsp, "OCSP %p \"%s\" request is:\n",
-		ocsp, ocsp->cert->subject.name );
+		ocsp, x509_name ( ocsp->cert ) );
 	DBGC2_HDA ( ocsp, 0, builder->data, builder->len );
 
 	/* Parse certificate ID for comparison with response */
@@ -192,7 +192,7 @@ static int ocsp_request ( struct ocsp_check *ocsp ) {
 		      asn1_enter ( cert_id, ASN1_SEQUENCE ),
 		      asn1_enter ( cert_id, ASN1_SEQUENCE ) ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" could not locate certID: %s\n",
-		       ocsp, ocsp->cert->subject.name, strerror ( rc ) );
+		       ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 		return rc;
 	}
 
@@ -218,7 +218,7 @@ static int ocsp_uri_string ( struct ocsp_check *ocsp ) {
 	base_uri_string = ocsp->cert->extensions.auth_info.ocsp.uri;
 	if ( ! base_uri_string ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" has no OCSP URI\n",
-		       ocsp, ocsp->cert->subject.name );
+		       ocsp, x509_name ( ocsp->cert ) );
 		rc = -ENOTTY;
 		goto err_no_uri;
 	}
@@ -250,7 +250,7 @@ static int ocsp_uri_string ( struct ocsp_check *ocsp ) {
 		goto err_ocsp_uri;
 	}
 	DBGC2 ( ocsp, "OCSP %p \"%s\" URI is %s\n",
-		ocsp, ocsp->cert->subject.name, ocsp->uri_string );
+		ocsp, x509_name ( ocsp->cert ), ocsp->uri_string );
 
 	/* Success */
 	rc = 0;
@@ -327,14 +327,14 @@ static int ocsp_parse_response_status ( struct ocsp_check *ocsp,
 	memcpy ( &cursor, raw, sizeof ( cursor ) );
 	if ( ( rc = asn1_enter ( &cursor, ASN1_ENUMERATED ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" could not locate responseStatus: "
-		       "%s\n", ocsp, ocsp->cert->subject.name, strerror ( rc ));
+		       "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 		return rc;
 	}
 
 	/* Extract response status */
 	if ( cursor.len != sizeof ( status ) ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" invalid status:\n",
-		       ocsp, ocsp->cert->subject.name );
+		       ocsp, x509_name ( ocsp->cert ) );
 		DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 		return -EINVAL;
 	}
@@ -343,7 +343,7 @@ static int ocsp_parse_response_status ( struct ocsp_check *ocsp,
 	/* Check response status */
 	if ( status != OCSP_STATUS_SUCCESSFUL ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" response status %d\n",
-		       ocsp, ocsp->cert->subject.name, status );
+		       ocsp, x509_name ( ocsp->cert ), status );
 		return EPROTO_STATUS ( status );
 	}
 
@@ -368,7 +368,7 @@ static int ocsp_parse_response_type ( struct ocsp_check *ocsp,
 	/* Check responseType is "basic" */
 	if ( asn1_compare ( &oid_basic_response_type_cursor, &cursor ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" response type not supported:\n",
-		       ocsp, ocsp->cert->subject.name );
+		       ocsp, x509_name ( ocsp->cert ) );
 		DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 		return -ENOTSUP_RESPONSE_TYPE;
 	}
@@ -443,17 +443,17 @@ static int ocsp_parse_responder_id ( struct ocsp_check *ocsp,
 	switch ( type ) {
 	case ASN1_EXPLICIT_TAG ( 1 ) :
 		DBGC2 ( ocsp, "OCSP %p \"%s\" responder identified by name\n",
-			ocsp, ocsp->cert->subject.name );
+			ocsp, x509_name ( ocsp->cert ) );
 		responder->compare = ocsp_compare_responder_name;
 		return 0;
 	case ASN1_EXPLICIT_TAG ( 2 ) :
 		DBGC2 ( ocsp, "OCSP %p \"%s\" responder identified by key "
-			"hash\n", ocsp, ocsp->cert->subject.name );
+			"hash\n", ocsp, x509_name ( ocsp->cert ) );
 		responder->compare = ocsp_compare_responder_key_hash;
 		return 0;
 	default:
 		DBGC ( ocsp, "OCSP %p \"%s\" unsupported responder ID type "
-		       "%d\n", ocsp, ocsp->cert->subject.name, type );
+		       "%d\n", ocsp, x509_name ( ocsp->cert ), type );
 		return -ENOTSUP_RESPONDER_ID;
 	}
 }
@@ -474,7 +474,7 @@ static int ocsp_parse_cert_id ( struct ocsp_check *ocsp,
 	asn1_shrink_any ( &cursor );
 	if ( asn1_compare ( &cursor, &ocsp->request.cert_id ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" certID mismatch:\n",
-		       ocsp, ocsp->cert->subject.name );
+		       ocsp, x509_name ( ocsp->cert ) );
 		DBGC_HDA ( ocsp, 0, ocsp->request.cert_id.data,
 			   ocsp->request.cert_id.len );
 		DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
@@ -512,7 +512,7 @@ static int ocsp_parse_responses ( struct ocsp_check *ocsp,
 	/* Check certStatus */
 	if ( asn1_type ( &cursor ) != ASN1_IMPLICIT_TAG ( 0 ) ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" non-good certStatus:\n",
-		       ocsp, ocsp->cert->subject.name );
+		       ocsp, x509_name ( ocsp->cert ) );
 		DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 		return -EACCES_CERT_STATUS;
 	}
@@ -522,11 +522,11 @@ static int ocsp_parse_responses ( struct ocsp_check *ocsp,
 	if ( ( rc = asn1_generalized_time ( &cursor,
 					    &response->this_update ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" could not parse thisUpdate: %s\n",
-		       ocsp, ocsp->cert->subject.name, strerror ( rc ) );
+		       ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 		return rc;
 	}
 	DBGC2 ( ocsp, "OCSP %p \"%s\" this update was at time %lld\n",
-		ocsp, ocsp->cert->subject.name, response->this_update );
+		ocsp, x509_name ( ocsp->cert ), response->this_update );
 	asn1_skip_any ( &cursor );
 
 	/* Parse nextUpdate, if present */
@@ -536,11 +536,11 @@ static int ocsp_parse_responses ( struct ocsp_check *ocsp,
 					     &response->next_update ) ) != 0 ) {
 			DBGC ( ocsp, "OCSP %p \"%s\" could not parse "
 			       "nextUpdate: %s\n", ocsp,
-			       ocsp->cert->subject.name, strerror ( rc ) );
+			       x509_name ( ocsp->cert ), strerror ( rc ) );
 			return rc;
 		}
 		DBGC2 ( ocsp, "OCSP %p \"%s\" next update is at time %lld\n",
-			ocsp, ocsp->cert->subject.name, response->next_update );
+			ocsp, x509_name ( ocsp->cert ), response->next_update );
 	} else {
 		/* If no nextUpdate is present, this indicates that
 		 * "newer revocation information is available all the
@@ -550,7 +550,7 @@ static int ocsp_parse_responses ( struct ocsp_check *ocsp,
 		 * time and it would still be valid.
 		 */
 		DBGC ( ocsp, "OCSP %p \"%s\" responder is a moron\n",
-		       ocsp, ocsp->cert->subject.name );
+		       ocsp, x509_name ( ocsp->cert ) );
 		response->next_update = time ( NULL );
 	}
 
@@ -630,7 +630,7 @@ static int ocsp_parse_certs ( struct ocsp_check *ocsp,
 					       &cert ) ) != 0 ) {
 			DBGC ( ocsp, "OCSP %p \"%s\" could not parse "
 			       "certificate: %s\n", ocsp,
-			       ocsp->cert->subject.name, strerror ( rc ) );
+			       x509_name ( ocsp->cert ), strerror ( rc ) );
 			DBGC_HDA ( ocsp, 0, cursor.data, cursor.len );
 			return rc;
 		}
@@ -638,9 +638,10 @@ static int ocsp_parse_certs ( struct ocsp_check *ocsp,
 		/* Use if this certificate matches the responder ID */
 		if ( response->responder.compare ( ocsp, cert ) == 0 ) {
 			response->signer = cert;
-			DBGC2 ( ocsp, "OCSP %p \"%s\" response is signed by "
-				"\"%s\"\n", ocsp, ocsp->cert->subject.name,
-				response->signer->subject.name );
+			DBGC2 ( ocsp, "OCSP %p \"%s\" response is signed by ",
+				ocsp, x509_name ( ocsp->cert ) );
+			DBGC2 ( ocsp, "\"%s\"\n",
+				x509_name ( response->signer ) );
 			return 0;
 		}
 
@@ -650,7 +651,7 @@ static int ocsp_parse_certs ( struct ocsp_check *ocsp,
 	}
 
 	DBGC ( ocsp, "OCSP %p \"%s\" missing responder certificate\n",
-	       ocsp, ocsp->cert->subject.name );
+	       ocsp, x509_name ( ocsp->cert ) );
 	return -EACCES_NO_RESPONDER;
 }
 
@@ -682,17 +683,17 @@ static int ocsp_parse_basic_response ( struct ocsp_check *ocsp,
 	if ( ( rc = asn1_signature_algorithm ( &cursor, algorithm ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" cannot parse signature "
 		       "algorithm: %s\n",
-		       ocsp, ocsp->cert->subject.name, strerror ( rc ) );
+		       ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 		return rc;
 	}
 	DBGC2 ( ocsp, "OCSP %p \"%s\" signature algorithm is %s\n",
-		ocsp, ocsp->cert->subject.name, (*algorithm)->name );
+		ocsp, x509_name ( ocsp->cert ), (*algorithm)->name );
 	asn1_skip_any ( &cursor );
 
 	/* Parse signature */
 	if ( ( rc = asn1_integral_bit_string ( &cursor, signature ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" cannot parse signature: %s\n",
-		       ocsp, ocsp->cert->subject.name, strerror ( rc ) );
+		       ocsp, x509_name ( ocsp->cert ), strerror ( rc ) );
 		return rc;
 	}
 	asn1_skip_any ( &cursor );
@@ -836,7 +837,7 @@ static int ocsp_check_signature ( struct ocsp_check *ocsp,
 	if ( ( rc = pubkey_init ( pubkey, pubkey_ctx, public_key->raw.data,
 				  public_key->raw.len ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" could not initialise public key: "
-		       "%s\n", ocsp, ocsp->cert->subject.name, strerror ( rc ));
+		       "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 		goto err_init;
 	}
 
@@ -845,12 +846,12 @@ static int ocsp_check_signature ( struct ocsp_check *ocsp,
 				    response->signature.data,
 				    response->signature.len ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" signature verification failed: "
-		       "%s\n", ocsp, ocsp->cert->subject.name, strerror ( rc ));
+		       "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 		goto err_verify;
 	}
 
 	DBGC2 ( ocsp, "OCSP %p \"%s\" signature is correct\n",
-		ocsp, ocsp->cert->subject.name );
+		ocsp, x509_name ( ocsp->cert ) );
 
  err_verify:
 	pubkey_final ( pubkey, pubkey_ctx );
@@ -892,10 +893,10 @@ int ocsp_validate ( struct ocsp_check *ocsp, time_t time ) {
 		x509_invalidate ( signer );
 		if ( ( rc = x509_validate ( signer, ocsp->issuer, time,
 					    &ocsp_root ) ) != 0 ) {
-			DBGC ( ocsp, "OCSP %p \"%s\" could not validate "
-			       "signer \"%s\": %s\n", ocsp,
-			       ocsp->cert->subject.name, signer->subject.name,
-			       strerror ( rc ) );
+			DBGC ( ocsp, "OCSP %p \"%s\" could not validate ",
+			       ocsp, x509_name ( ocsp->cert ) );
+			DBGC ( ocsp, "signer \"%s\": %s\n",
+			       x509_name ( signer ), strerror ( rc ) );
 			return rc;
 		}
 
@@ -904,9 +905,10 @@ int ocsp_validate ( struct ocsp_check *ocsp, time_t time ) {
 		 */
 		if ( ! ( signer->extensions.ext_usage.bits &
 			 X509_OCSP_SIGNING ) ) {
-			DBGC ( ocsp, "OCSP %p \"%s\" signer \"%s\" is "
-			       "not an OCSP-signing certificate\n", ocsp,
-			       ocsp->cert->subject.name, signer->subject.name );
+			DBGC ( ocsp, "OCSP %p \"%s\" ",
+			       ocsp, x509_name ( ocsp->cert ) );
+			DBGC ( ocsp, "signer \"%s\" is not an OCSP-signing "
+			       "certificate\n", x509_name ( signer ) );
 			return -EACCES_NON_OCSP_SIGNING;
 		}
 	}
@@ -920,16 +922,16 @@ int ocsp_validate ( struct ocsp_check *ocsp, time_t time ) {
 	 */
 	if ( response->this_update > ( time + X509_ERROR_MARGIN_TIME ) ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" response is not yet valid (at "
-		       "time %lld)\n", ocsp, ocsp->cert->subject.name, time );
+		       "time %lld)\n", ocsp, x509_name ( ocsp->cert ), time );
 		return -EACCES_STALE;
 	}
 	if ( response->next_update < ( time - X509_ERROR_MARGIN_TIME ) ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" response is stale (at time "
-		       "%lld)\n", ocsp, ocsp->cert->subject.name, time );
+		       "%lld)\n", ocsp, x509_name ( ocsp->cert ), time );
 		return -EACCES_STALE;
 	}
 	DBGC2 ( ocsp, "OCSP %p \"%s\" response is valid (at time %lld)\n",
-		ocsp, ocsp->cert->subject.name, time );
+		ocsp, x509_name ( ocsp->cert ), time );
 
 	/* Mark certificate as passing OCSP verification */
 	ocsp->cert->extensions.auth_info.ocsp.good = 1;
@@ -938,11 +940,12 @@ int ocsp_validate ( struct ocsp_check *ocsp, time_t time ) {
 	if ( ( rc = x509_validate ( ocsp->cert, ocsp->issuer, time,
 				    &ocsp_root ) ) != 0 ) {
 		DBGC ( ocsp, "OCSP %p \"%s\" could not validate certificate: "
-		       "%s\n", ocsp, ocsp->cert->subject.name, strerror ( rc ));
+		       "%s\n", ocsp, x509_name ( ocsp->cert ), strerror ( rc ));
 		return rc;
 	}
-	DBGC ( ocsp, "OCSP %p \"%s\" successfully validated using \"%s\"\n",
-	       ocsp, ocsp->cert->subject.name, signer->subject.name );
+	DBGC ( ocsp, "OCSP %p \"%s\" successfully validated ",
+	       ocsp, x509_name ( ocsp->cert ) );
+	DBGC ( ocsp, "using \"%s\"\n", x509_name ( signer ) );
 
 	return 0;
 }
diff --git a/src/crypto/x509.c b/src/crypto/x509.c
index d54124c5..eb7d5029 100644
--- a/src/crypto/x509.c
+++ b/src/crypto/x509.c
@@ -103,11 +103,34 @@ FILE_LICENCE ( GPL2_OR_LATER );
 	__einfo_error ( EINFO_EACCES_OCSP_REQUIRED )
 #define EINFO_EACCES_OCSP_REQUIRED \
 	__einfo_uniqify ( EINFO_EACCES, 0x09, "OCSP check required" )
+#define EACCES_WRONG_NAME \
+	__einfo_error ( EINFO_EACCES_WRONG_NAME )
+#define EINFO_EACCES_WRONG_NAME \
+	__einfo_uniqify ( EINFO_EACCES, 0x0a, "Incorrect certificate name" )
 
 /** Certificate cache */
 static LIST_HEAD ( x509_cache );
 
 /**
+ * Get X.509 certificate name (for debugging)
+ *
+ * @v cert		X.509 certificate
+ * @ret name		Name (for debugging)
+ */
+const char * x509_name ( struct x509_certificate *cert ) {
+	struct asn1_cursor *common_name = &cert->subject.common_name;
+	static char buf[64];
+	size_t len;
+
+	len = common_name->len;
+	if ( len > ( sizeof ( buf ) - 1 /* NUL */ ) )
+		len = ( sizeof ( buf ) - 1 /* NUL */ );
+	memcpy ( buf, common_name->data, len );
+	buf[len] = '\0';
+	return buf;
+}
+
+/**
  * Free X.509 certificate
  *
  * @v refcnt		Reference count
@@ -117,7 +140,6 @@ static void x509_free ( struct refcnt *refcnt ) {
 		container_of ( refcnt, struct x509_certificate, refcnt );
 
 	DBGC2 ( cert, "X509 %p freed\n", cert );
-	free ( cert->subject.name );
 	free ( cert->extensions.auth_info.ocsp.uri );
 	free ( cert );
 }
@@ -292,11 +314,10 @@ static int x509_parse_validity ( struct x509_certificate *cert,
  * Parse X.509 certificate common name
  *
  * @v cert		X.509 certificate
- * @v name		Common name to fill in
  * @v raw		ASN.1 cursor
  * @ret rc		Return status code
  */
-static int x509_parse_common_name ( struct x509_certificate *cert, char **name,
+static int x509_parse_common_name ( struct x509_certificate *cert,
 				    const struct asn1_cursor *raw ) {
 	struct asn1_cursor cursor;
 	struct asn1_cursor oid_cursor;
@@ -325,19 +346,9 @@ static int x509_parse_common_name ( struct x509_certificate *cert, char **name,
 			return rc;
 		}
 
-		/* Allocate and copy name */
-		*name = zalloc ( name_cursor.len + 1 /* NUL */ );
-		if ( ! *name )
-			return -ENOMEM;
-		memcpy ( *name, name_cursor.data, name_cursor.len );
-
-		/* Check that name contains no NULs */
-		if ( strlen ( *name ) != name_cursor.len ) {
-			DBGC ( cert, "X509 %p contains malicious commonName:\n",
-			       cert );
-			DBGC_HDA ( cert, 0, raw->data, raw->len );
-			return rc;
-		}
+		/* Record common name */
+		memcpy ( &cert->subject.common_name, &name_cursor,
+			 sizeof ( cert->subject.common_name ) );
 
 		return 0;
 	}
@@ -357,7 +368,6 @@ static int x509_parse_common_name ( struct x509_certificate *cert, char **name,
 static int x509_parse_subject ( struct x509_certificate *cert,
 				const struct asn1_cursor *raw ) {
 	struct x509_subject *subject = &cert->subject;
-	char **name = &subject->name;
 	int rc;
 
 	/* Record raw subject */
@@ -367,9 +377,10 @@ static int x509_parse_subject ( struct x509_certificate *cert,
 	DBGC2_HDA ( cert, 0, subject->raw.data, subject->raw.len );
 
 	/* Parse common name */
-	if ( ( rc = x509_parse_common_name ( cert, name, raw ) ) != 0 )
+	if ( ( rc = x509_parse_common_name ( cert, raw ) ) != 0 )
 		return rc;
-	DBGC2 ( cert, "X509 %p common name is \"%s\":\n", cert, *name );
+	DBGC2 ( cert, "X509 %p common name is \"%s\":\n", cert,
+		x509_name ( cert ) );
 
 	return 0;
 }
@@ -1045,7 +1056,7 @@ int x509_certificate ( const void *data, size_t len,
 		if ( asn1_compare ( &cursor, &(*cert)->raw ) == 0 ) {
 
 			DBGC2 ( *cert, "X509 %p \"%s\" cache hit\n",
-				*cert, (*cert)->subject.name );
+				*cert, x509_name ( *cert ) );
 
 			/* Mark as most recently used */
 			list_del ( &(*cert)->list );
@@ -1109,14 +1120,14 @@ static int x509_check_signature ( struct x509_certificate *cert,
 	digest_init ( digest, digest_ctx );
 	digest_update ( digest, digest_ctx, cert->tbs.data, cert->tbs.len );
 	digest_final ( digest, digest_ctx, digest_out );
-	DBGC2 ( cert, "X509 %p \"%s\" digest:\n", cert, cert->subject.name );
+	DBGC2 ( cert, "X509 %p \"%s\" digest:\n", cert, x509_name ( cert ) );
 	DBGC2_HDA ( cert, 0, digest_out, sizeof ( digest_out ) );
 
 	/* Check that signature public key algorithm matches signer */
 	if ( public_key->algorithm->pubkey != pubkey ) {
 		DBGC ( cert, "X509 %p \"%s\" signature algorithm %s does not "
 		       "match signer's algorithm %s\n",
-		       cert, cert->subject.name, algorithm->name,
+		       cert, x509_name ( cert ), algorithm->name,
 		       public_key->algorithm->name );
 		rc = -EINVAL_ALGORITHM_MISMATCH;
 		goto err_mismatch;
@@ -1126,14 +1137,14 @@ static int x509_check_signature ( struct x509_certificate *cert,
 	if ( ( rc = pubkey_init ( pubkey, pubkey_ctx, public_key->raw.data,
 				  public_key->raw.len ) ) != 0 ) {
 		DBGC ( cert, "X509 %p \"%s\" cannot initialise public key: "
-		       "%s\n", cert, cert->subject.name, strerror ( rc ) );
+		       "%s\n", cert, x509_name ( cert ), strerror ( rc ) );
 		goto err_pubkey_init;
 	}
 	if ( ( rc = pubkey_verify ( pubkey, pubkey_ctx, digest, digest_out,
 				    signature->value.data,
 				    signature->value.len ) ) != 0 ) {
 		DBGC ( cert, "X509 %p \"%s\" signature verification failed: "
-		       "%s\n", cert, cert->subject.name, strerror ( rc ) );
+		       "%s\n", cert, x509_name ( cert ), strerror ( rc ) );
 		goto err_pubkey_verify;
 	}
 
@@ -1172,9 +1183,10 @@ int x509_check_issuer ( struct x509_certificate *cert,
 	 * for some enjoyable ranting on this subject.
 	 */
 	if ( asn1_compare ( &cert->issuer.raw, &issuer->subject.raw ) != 0 ) {
-		DBGC ( cert, "X509 %p \"%s\" issuer does not match X509 %p "
-		       "\"%s\" subject\n", cert, cert->subject.name,
-		       issuer, issuer->subject.name );
+		DBGC ( cert, "X509 %p \"%s\" issuer does not match ",
+		       cert, x509_name ( cert ) );
+		DBGC ( cert, "X509 %p \"%s\" subject\n",
+		       issuer, x509_name ( issuer ) );
 		DBGC_HDA ( cert, 0, cert->issuer.raw.data,
 			   cert->issuer.raw.len );
 		DBGC_HDA ( issuer, 0, issuer->subject.raw.data,
@@ -1184,16 +1196,18 @@ int x509_check_issuer ( struct x509_certificate *cert,
 
 	/* Check that issuer is allowed to sign certificates */
 	if ( ! issuer->extensions.basic.ca ) {
-		DBGC ( issuer, "X509 %p \"%s\" cannot sign X509 %p \"%s\": "
-		       "not a CA certificate\n", issuer, issuer->subject.name,
-		       cert, cert->subject.name );
+		DBGC ( issuer, "X509 %p \"%s\" cannot sign ",
+		       issuer, x509_name ( issuer ) );
+		DBGC ( issuer, "X509 %p \"%s\": not a CA certificate\n",
+		       cert, x509_name ( cert ) );
 		return -EACCES_NOT_CA;
 	}
 	if ( issuer->extensions.usage.present &&
 	     ( ! ( issuer->extensions.usage.bits & X509_KEY_CERT_SIGN ) ) ) {
-		DBGC ( issuer, "X509 %p \"%s\" cannot sign X509 %p \"%s\": "
-		       "no keyCertSign usage\n", issuer, issuer->subject.name,
-		       cert, cert->subject.name );
+		DBGC ( issuer, "X509 %p \"%s\" cannot sign ",
+		       issuer, x509_name ( issuer ) );
+		DBGC ( issuer, "X509 %p \"%s\": no keyCertSign usage\n",
+		       cert, x509_name ( cert ) );
 		return -EACCES_KEY_USAGE;
 	}
 
@@ -1243,14 +1257,14 @@ int x509_check_root ( struct x509_certificate *cert, struct x509_root *root ) {
 		if ( memcmp ( fingerprint, root_fingerprint,
 			      sizeof ( fingerprint ) ) == 0 ) {
 			DBGC ( cert, "X509 %p \"%s\" is a root certificate\n",
-			       cert, cert->subject.name );
+			       cert, x509_name ( cert ) );
 			return 0;
 		}
 		root_fingerprint += sizeof ( fingerprint );
 	}
 
 	DBGC2 ( cert, "X509 %p \"%s\" is not a root certificate\n",
-		cert, cert->subject.name );
+		cert, x509_name ( cert ) );
 	return -ENOENT;
 }
 
@@ -1267,17 +1281,17 @@ int x509_check_time ( struct x509_certificate *cert, time_t time ) {
 	/* Check validity period */
 	if ( validity->not_before.time > ( time + X509_ERROR_MARGIN_TIME ) ) {
 		DBGC ( cert, "X509 %p \"%s\" is not yet valid (at time %lld)\n",
-		       cert, cert->subject.name, time );
+		       cert, x509_name ( cert ), time );
 		return -EACCES_EXPIRED;
 	}
 	if ( validity->not_after.time < ( time - X509_ERROR_MARGIN_TIME ) ) {
 		DBGC ( cert, "X509 %p \"%s\" has expired (at time %lld)\n",
-		       cert, cert->subject.name, time );
+		       cert, x509_name ( cert ), time );
 		return -EACCES_EXPIRED;
 	}
 
 	DBGC2 ( cert, "X509 %p \"%s\" is valid (at time %lld)\n",
-		cert, cert->subject.name, time );
+		cert, x509_name ( cert ), time );
 	return 0;
 }
 
@@ -1324,15 +1338,15 @@ int x509_validate ( struct x509_certificate *cert,
 	/* Fail unless we have an issuer */
 	if ( ! issuer ) {
 		DBGC2 ( cert, "X509 %p \"%s\" has no issuer\n",
-			cert, cert->subject.name );
+			cert, x509_name ( cert ) );
 		return -EACCES_UNTRUSTED;
 	}
 
 	/* Fail unless issuer has already been validated */
 	if ( ! issuer->valid ) {
-		DBGC ( cert, "X509 %p \"%s\" issuer %p \"%s\" has not yet "
-		       "been validated\n", cert, cert->subject.name,
-		       issuer, issuer->subject.name );
+		DBGC ( cert, "X509 %p \"%s\" ", cert, x509_name ( cert ) );
+		DBGC ( cert, "issuer %p \"%s\" has not yet been validated\n",
+		       issuer, x509_name ( issuer ) );
 		return -EACCES_OUT_OF_ORDER;
 	}
 
@@ -1342,9 +1356,9 @@ int x509_validate ( struct x509_certificate *cert,
 
 	/* Fail if path length constraint is violated */
 	if ( issuer->path_remaining == 0 ) {
-		DBGC ( cert, "X509 %p \"%s\" issuer %p \"%s\" path length "
-		       "exceeded\n", cert, cert->subject.name,
-		       issuer, issuer->subject.name );
+		DBGC ( cert, "X509 %p \"%s\" ", cert, x509_name ( cert ) );
+		DBGC ( cert, "issuer %p \"%s\" path length exceeded\n",
+		       issuer, x509_name ( issuer ) );
 		return -EACCES_PATH_LEN;
 	}
 
@@ -1352,7 +1366,7 @@ int x509_validate ( struct x509_certificate *cert,
 	if ( cert->extensions.auth_info.ocsp.uri &&
 	     ( ! cert->extensions.auth_info.ocsp.good ) ) {
 		DBGC ( cert, "X509 %p \"%s\" requires an OCSP check\n",
-		       cert, cert->subject.name );
+		       cert, x509_name ( cert ) );
 		return -EACCES_OCSP_REQUIRED;
 	}
 
@@ -1365,9 +1379,31 @@ int x509_validate ( struct x509_certificate *cert,
 	/* Mark certificate as valid */
 	cert->valid = 1;
 
-	DBGC ( cert, "X509 %p \"%s\" successfully validated using issuer %p "
-	       "\"%s\"\n", cert, cert->subject.name,
-	       issuer, issuer->subject.name );
+	DBGC ( cert, "X509 %p \"%s\" successfully validated using ",
+	       cert, x509_name ( cert ) );
+	DBGC ( cert, "issuer %p \"%s\"\n", issuer, x509_name ( issuer ) );
+	return 0;
+}
+
+/**
+ * Check X.509 certificate name
+ *
+ * @v cert		X.509 certificate
+ * @v name		Name
+ * @ret rc		Return status code
+ */
+int x509_check_name ( struct x509_certificate *cert, const char *name ) {
+	struct asn1_cursor *common_name = &cert->subject.common_name;
+	size_t len = strlen ( name );
+
+	/* Check commonName */
+	if ( ! ( ( len == common_name->len ) &&
+		 ( memcmp ( name, common_name->data, len ) == 0 ) ) ) {
+		DBGC ( cert, "X509 %p \"%s\" does not match name \"%s\"\n",
+		       cert, x509_name ( cert ), name );
+		return -EACCES_WRONG_NAME;
+	}
+
 	return 0;
 }
 
@@ -1435,7 +1471,7 @@ int x509_append ( struct x509_chain *chain, struct x509_certificate *cert ) {
 	link->cert = x509_get ( cert );
 	list_add_tail ( &link->list, &chain->links );
 	DBGC ( chain, "X509 chain %p added X509 %p \"%s\"\n",
-	       chain, cert, cert->subject.name );
+	       chain, cert, x509_name ( cert ) );
 
 	return 0;
 }
diff --git a/src/include/ipxe/x509.h b/src/include/ipxe/x509.h
index a47942a7..3e4bcd20 100644
--- a/src/include/ipxe/x509.h
+++ b/src/include/ipxe/x509.h
@@ -65,7 +65,7 @@ struct x509_subject {
 	/** Raw subject */
 	struct asn1_cursor raw;
 	/** Common name */
-	char *name;
+	struct asn1_cursor common_name;
 	/** Public key information */
 	struct x509_public_key public_key;
 };
@@ -330,11 +330,14 @@ struct x509_root {
 	const void *fingerprints;
 };
 
+extern const char * x509_name ( struct x509_certificate *cert );
+
 extern int x509_certificate ( const void *data, size_t len,
 			      struct x509_certificate **cert );
 extern int x509_validate ( struct x509_certificate *cert,
 			   struct x509_certificate *issuer,
 			   time_t time, struct x509_root *root );
+extern int x509_check_name ( struct x509_certificate *cert, const char *name );
 
 extern struct x509_chain * x509_alloc_chain ( void );
 extern int x509_append ( struct x509_chain *chain,
diff --git a/src/net/tls.c b/src/net/tls.c
index 5e18f726..742a7c0b 100644
--- a/src/net/tls.c
+++ b/src/net/tls.c
@@ -49,10 +49,6 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <ipxe/tls.h>
 
 /* Disambiguate the various error causes */
-#define EACCES_WRONG_NAME __einfo_error ( EINFO_EACCES_WRONG_NAME )
-#define EINFO_EACCES_WRONG_NAME						\
-	__einfo_uniqify ( EINFO_EACCES, 0x02,				\
-			  "Incorrect server name" )
 #define EINVAL_CHANGE_CIPHER __einfo_error ( EINFO_EINVAL_CHANGE_CIPHER )
 #define EINFO_EINVAL_CHANGE_CIPHER					\
 	__einfo_uniqify ( EINFO_EINVAL, 0x01,				\
@@ -1479,7 +1475,7 @@ static int tls_parse_chain ( struct tls_session *tls,
 		}
 		cert = x509_last ( tls->chain );
 		DBGC ( tls, "TLS %p found certificate %s\n",
-		       tls, cert->subject.name );
+		       tls, x509_name ( cert ) );
 
 		/* Move to next certificate in list */
 		data = next;
@@ -2454,11 +2450,9 @@ 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 ) ) {
-		DBGC ( tls, "TLS %p server name incorrect (expected %s, got "
-		       "%s)\n", tls, tls->name, cert->subject.name );
-		rc = -EACCES_WRONG_NAME;
+	if ( ( rc = x509_check_name ( cert, tls->name ) ) != 0 ) {
+		DBGC ( tls, "TLS %p server certificate does not match %s: %s\n",
+		       tls, tls->name, strerror ( rc ) );
 		goto err;
 	}
 
diff --git a/src/net/validator.c b/src/net/validator.c
index 1de3bb9d..7913ed64 100644
--- a/src/net/validator.c
+++ b/src/net/validator.c
@@ -179,7 +179,7 @@ static int validator_append ( struct validator *validator,
 		}
 		cert = x509_last ( certs );
 		DBGC ( validator, "VALIDATOR %p found certificate %s\n",
-		       validator, cert->subject.name );
+		       validator, x509_name ( cert ) );
 
 		/* Move to next certificate */
 		asn1_skip_any ( &cursor );