[crypto] Add x509_auto_append()

CMS includes an unordered certificate set, from which certificates
must be extracted in order by matching up issuers with subjects.  We
will use the same functionality as part of the automatic download of
cross-signing certificates.  Generalise cms_find_subject() to
x509_find_subject(), and create x509_auto_append().

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

src/crypto/cms.c

@@ -175,31 +175,6 @@ cms_find_issuer_serial ( struct cms_signature *sig,
 	return NULL;
 }
 
-/**
- * Identify CMS signature certificate by subject
- *
- * @v sig		CMS signature
- * @v subject		Subject
- * @ret cert		X.509 certificate, or NULL if not found
- */
-static struct x509_certificate *
-cms_find_subject ( struct cms_signature *sig,
-		   const struct asn1_cursor *subject ) {
-	struct x509_link *link;
-	struct x509_certificate *cert;
-
-	/* Scan through certificate list */
-	list_for_each_entry ( link, &sig->certificates->links, list ) {
-
-		/* Check subject */
-		cert = link->cert;
-		if ( asn1_compare ( subject, &cert->subject.raw ) == 0 )
-			return cert;
-	}
-
-	return NULL;
-}
-
 /**
  * Parse CMS signature signer identifier
  *
@@ -215,7 +190,6 @@ static int cms_parse_signer_identifier ( struct cms_signature *sig,
 	struct asn1_cursor serial;
 	struct asn1_cursor issuer;
 	struct x509_certificate *cert;
-	struct x509_certificate *previous;
 	int rc;
 
 	/* Enter issuerAndSerialNumber */
@@ -253,22 +227,20 @@ static int cms_parse_signer_identifier ( struct cms_signature *sig,
 		return -ENOENT;
 	}
 
-	/* Create certificate chain */
-	do {
-		/* Add certificate to chain */
-		if ( ( rc = x509_append ( info->chain, cert ) ) != 0 ) {
-			DBGC ( sig, "CMS %p/%p could not append certificate: "
-			       "%s\n", sig, info, strerror ( rc ) );
-			return rc;
-		}
-		DBGC ( sig, "CMS %p/%p added certificate %s\n",
-		       sig, info, cert->subject.name );
+	/* Append certificate to chain */
+	if ( ( rc = x509_append ( info->chain, cert ) ) != 0 ) {
+		DBGC ( sig, "CMS %p/%p could not append certificate: %s\n",
+		       sig, info, strerror ( rc ) );
+		return rc;
+	}
 
-		/* Locate next certificate in chain, if any */
-		previous = cert;
-		cert = cms_find_subject ( sig, &cert->issuer.raw );
-
-	} while ( ( cert != NULL ) && ( cert != previous ) );
+	/* Append remaining certificates to chain */
+	if ( ( rc = x509_auto_append ( info->chain,
+				       sig->certificates ) ) != 0 ) {
+		DBGC ( sig, "CMS %p/%p could not append certificates: %s\n",
+		       sig, info, strerror ( rc ) );
+		return rc;
+	}
 
 	return 0;
 }

src/crypto/x509.c

@@ -1678,6 +1678,72 @@ int x509_append_raw ( struct x509_chain *chain, const void *data,
 	return rc;
 }
 
+/**
+ * Identify X.509 certificate by subject
+ *
+ * @v certs		X.509 certificate list
+ * @v subject		Subject
+ * @ret cert		X.509 certificate, or NULL if not found
+ */
+static struct x509_certificate *
+x509_find_subject ( struct x509_chain *certs,
+		    const struct asn1_cursor *subject ) {
+	struct x509_link *link;
+	struct x509_certificate *cert;
+
+	/* Scan through certificate list */
+	list_for_each_entry ( link, &certs->links, list ) {
+
+		/* Check subject */
+		cert = link->cert;
+		if ( asn1_compare ( subject, &cert->subject.raw ) == 0 )
+			return cert;
+	}
+
+	return NULL;
+}
+
+/**
+ * Append X.509 certificates to X.509 certificate chain
+ *
+ * @v chain		X.509 certificate chain
+ * @v certs		X.509 certificate list
+ * @ret rc		Return status code
+ *
+ * Certificates will be automatically appended to the chain based upon
+ * the subject and issuer names.
+ */
+int x509_auto_append ( struct x509_chain *chain, struct x509_chain *certs ) {
+	struct x509_certificate *cert;
+	struct x509_certificate *previous;
+	int rc;
+
+	/* Get current certificate */
+	cert = x509_last ( chain );
+	if ( ! cert ) {
+		DBGC ( chain, "X509 chain %p has no certificates\n", chain );
+		return -EINVAL;
+	}
+
+	/* Append certificates, in order */
+	while ( 1 ) {
+
+		/* Find issuing certificate */
+		previous = cert;
+		cert = x509_find_subject ( certs, &cert->issuer.raw );
+		if ( ! cert )
+			break;
+		if ( cert == previous )
+			break;
+
+		/* Append certificate to chain */
+		if ( ( rc = x509_append ( chain, cert ) ) != 0 )
+			return rc;
+	}
+
+	return 0;
+}
+
 /**
  * Validate X.509 certificate chain
  *

src/include/ipxe/x509.h

@@ -335,6 +335,8 @@ extern int x509_append ( struct x509_chain *chain,
 			 struct x509_certificate *cert );
 extern int x509_append_raw ( struct x509_chain *chain, const void *data,
 			     size_t len );
+extern int x509_auto_append ( struct x509_chain *chain,
+			      struct x509_chain *certs );
 extern int x509_validate_chain ( struct x509_chain *chain, time_t time,
 				 struct x509_root *root );