wget: run s_client helper with -servername HOST

This is necessary for multi-hosted TLSed web sites.

function                                             old     new   delta
spawn_https_helper_openssl                           334     441    +107

Based on a patch by Jeremy Chadwick <jdc@koitsu.org>

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 44 insertions, 5 deletions

diff --git a/networking/wget.c b/networking/wget.c
index 37950ed..653d807 100644
--- a/networking/wget.c
+++ b/networking/wget.c
@@ -62,9 +62,10 @@
 //config:	  a helper program to talk over HTTPS.
 //config:
 //config:	  OpenSSL has a simple SSL client for debug purposes.
-//config:	  If you select "openssl" helper, wget will effectively call
-//config:	  "openssl s_client -quiet -connect IP:443 2>/dev/null"
-//config:	  and pipe its data through it.
+//config:	  If you select "openssl" helper, wget will effectively run:
+//config:	  "openssl s_client -quiet -connect hostname:443
+//config:	  -servername hostname 2>/dev/null" and pipe its data
+//config:	  through it. -servername is not used if hostname is numeric.
 //config:	  Note inconvenient API: host resolution is done twice,
 //config:	  and there is no guarantee openssl's idea of IPv6 address
 //config:	  format is the same as ours.
@@ -349,6 +350,30 @@ static void set_alarm(void)
 # define clear_alarm() ((void)0)
 #endif
 
+#if ENABLE_FEATURE_WGET_OPENSSL
+/*
+ * is_ip_address() attempts to verify whether or not a string
+ * contains an IPv4 or IPv6 address (vs. an FQDN).  The result
+ * of inet_pton() can be used to determine this.
+ *
+ * TODO add proper error checking when inet_pton() returns -1
+ * (some form of system error has occurred, and errno is set)
+ */
+static int is_ip_address(const char *string)
+{
+	struct sockaddr_in sa;
+
+	int result = inet_pton(AF_INET, string, &(sa.sin_addr));
+# if ENABLE_FEATURE_IPV6
+	if (result == 0) {
+		struct sockaddr_in6 sa6;
+		result = inet_pton(AF_INET6, string, &(sa6.sin6_addr));
+	}
+# endif
+	return (result == 1);
+}
+#endif
+
 static FILE *open_socket(len_and_sockaddr *lsa)
 {
 	int fd;
@@ -629,6 +654,7 @@ static FILE* prepare_ftp_session(FILE **dfpp, struct host_info *target, len_and_
 static int spawn_https_helper_openssl(const char *host, unsigned port)
 {
 	char *allocated = NULL;
+	char *servername;
 	int sp[2];
 	int pid;
 	IF_FEATURE_WGET_SSL_HELPER(volatile int child_failed = 0;)
@@ -639,12 +665,14 @@ static int spawn_https_helper_openssl(const char *host, unsigned port)
 
 	if (!strchr(host, ':'))
 		host = allocated = xasprintf("%s:%u", host, port);
+	servername = xstrdup(host);
+	strrchr(servername, ':')[0] = '\0';
 
 	fflush_all();
 	pid = xvfork();
 	if (pid == 0) {
 		/* Child */
-		char *argv[6];
+		char *argv[8];
 
 		close(sp[0]);
 		xmove_fd(sp[1], 0);
@@ -656,12 +684,22 @@ static int spawn_https_helper_openssl(const char *host, unsigned port)
 		 */
 		xmove_fd(2, 3);
 		xopen("/dev/null", O_RDWR);
+		memset(&argv, 0, sizeof(argv));
 		argv[0] = (char*)"openssl";
 		argv[1] = (char*)"s_client";
 		argv[2] = (char*)"-quiet";
 		argv[3] = (char*)"-connect";
 		argv[4] = (char*)host;
-		argv[5] = NULL;
+		/*
+		 * Per RFC 6066 Section 3, the only permitted values in the
+		 * TLS server_name (SNI) field are FQDNs (DNS hostnames).
+		 * IPv4 and IPv6 addresses, port numbers are not allowed.
+		 */
+		if (!is_ip_address(servername)) {
+			argv[5] = (char*)"-servername";
+			argv[6] = (char*)servername;
+		}
+
 		BB_EXECVP(argv[0], argv);
 		xmove_fd(3, 2);
 # if ENABLE_FEATURE_WGET_SSL_HELPER
@@ -674,6 +712,7 @@ static int spawn_https_helper_openssl(const char *host, unsigned port)
 	}
 
 	/* Parent */
+	free(servername);
 	free(allocated);
 	close(sp[1]);
 # if ENABLE_FEATURE_WGET_SSL_HELPER