Merge branch 'ob/imap-send-ssl-verify' into maint

* ob/imap-send-ssl-verify:
  imap-send: support subjectAltName as well
  imap-send: the subject of SSL certificate must match the host
  imap-send: move #ifdef around

Author: gitster

imap-send.c

@@ -31,6 +31,7 @@ typedef void *SSL;
 #else
 #include <openssl/evp.h>
 #include <openssl/hmac.h>
+#include <openssl/x509v3.h>
 #endif
 
 struct store_conf {
@@ -266,19 +267,72 @@ static void socket_perror(const char *func, struct imap_socket *sock, int ret)
 	}
 }
 
+#ifdef NO_OPENSSL
 static int ssl_socket_connect(struct imap_socket *sock, int use_tls_only, int verify)
 {
-#ifdef NO_OPENSSL
 	fprintf(stderr, "SSL requested but SSL support not compiled in\n");
 	return -1;
+}
+
 #else
+
+static int host_matches(const char *host, const char *pattern)
+{
+	if (pattern[0] == '*' && pattern[1] == '.') {
+		pattern += 2;
+		if (!(host = strchr(host, '.')))
+			return 0;
+		host++;
+	}
+
+	return *host && *pattern && !strcasecmp(host, pattern);
+}
+
+static int verify_hostname(X509 *cert, const char *hostname)
+{
+	int len;
+	X509_NAME *subj;
+	char cname[1000];
+	int i, found;
+	STACK_OF(GENERAL_NAME) *subj_alt_names;
+
+	/* try the DNS subjectAltNames */
+	found = 0;
+	if ((subj_alt_names = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL))) {
+		int num_subj_alt_names = sk_GENERAL_NAME_num(subj_alt_names);
+		for (i = 0; !found && i < num_subj_alt_names; i++) {
+			GENERAL_NAME *subj_alt_name = sk_GENERAL_NAME_value(subj_alt_names, i);
+			if (subj_alt_name->type == GEN_DNS &&
+			    strlen((const char *)subj_alt_name->d.ia5->data) == (size_t)subj_alt_name->d.ia5->length &&
+			    host_matches(hostname, (const char *)(subj_alt_name->d.ia5->data)))
+				found = 1;
+		}
+		sk_GENERAL_NAME_pop_free(subj_alt_names, GENERAL_NAME_free);
+	}
+	if (found)
+		return 0;
+
+	/* try the common name */
+	if (!(subj = X509_get_subject_name(cert)))
+		return error("cannot get certificate subject");
+	if ((len = X509_NAME_get_text_by_NID(subj, NID_commonName, cname, sizeof(cname))) < 0)
+		return error("cannot get certificate common name");
+	if (strlen(cname) == (size_t)len && host_matches(hostname, cname))
+		return 0;
+	return error("certificate owner '%s' does not match hostname '%s'",
+		     cname, hostname);
+}
+
+static int ssl_socket_connect(struct imap_socket *sock, int use_tls_only, int verify)
+{
 #if (OPENSSL_VERSION_NUMBER >= 0x10000000L)
 	const SSL_METHOD *meth;
 #else
 	SSL_METHOD *meth;
 #endif
 	SSL_CTX *ctx;
 	int ret;
+	X509 *cert;
 
 	SSL_library_init();
 	SSL_load_error_strings();
@@ -322,9 +376,18 @@ static int ssl_socket_connect(struct imap_socket *sock, int use_tls_only, int ve
 		return -1;
 	}
 
+	if (verify) {
+		/* make sure the hostname matches that of the certificate */
+		cert = SSL_get_peer_certificate(sock->ssl);
+		if (!cert)
+			return error("unable to get peer certificate.");
+		if (verify_hostname(cert, server.host) < 0)
+			return -1;
+	}
+
 	return 0;
-#endif
 }
+#endif
 
 static int socket_read(struct imap_socket *sock, char *buf, int len)
 {