http: another cut at fixing HTTP framing

For keep-alive connections it's neither sufficient to cut at the end of
header (since the rest of the response would leak into next request), nor
just fan out the current SSL frame (since the SSL framing is effectively
undefined and we don't know if we're done yet and with non-blocking reads
we're likely to just terminate too early).

So, let's just obey the Content-Length header. If it's missing (chunked
encoding or standards violation) then read until the EOF, but still
succeed if the header was complete. This way we're hopefully on the safe
side.

configure.ac

@@ -8,6 +8,7 @@ AM_INIT_AUTOMAKE([foreign subdir-objects])
 
 # Checks for programs.
 AC_PROG_CC
+AC_GNU_SOURCE
 
 AM_SILENT_RULES([yes])
 
@@ -33,7 +34,7 @@ AC_TYPE_UINT8_T
 # Checks for library functions.
 AC_FUNC_MALLOC
 AC_FUNC_REALLOC
-AC_CHECK_FUNCS([bzero gethostbyname inet_ntoa memmove memset select socket strerror strstr strtol])
+AC_CHECK_FUNCS([bzero gethostbyname inet_ntoa memmove memset memmem select socket strerror strstr strtol])
 
 #AC_CONFIG_FILES([Makefile])
 AC_OUTPUT(Makefile)

src/http.c

@@ -87,6 +87,8 @@ int http_receive(struct tunnel *tunnel, char **response)
 	char *buffer, *res;
 	int n = 0;
 	int bytes_read = 0;
+	int header_size = 0;
+	int content_size = 0;
 
 	buffer = malloc(BUFSZ);
 	if (buffer == NULL)
@@ -97,11 +99,25 @@ int http_receive(struct tunnel *tunnel, char **response)
 				  (uint8_t *) buffer + bytes_read,
 				  BUFSZ - 1 - bytes_read);
 		if (n > 0) {
+			char *eoh;
+
 			bytes_read += n;
 
-			if (bytes_read >= 4
-			    && !memcmp(&buffer[bytes_read - 4], "\r\n\r\n", 4))
-				break;
+			if (header_size) {
+				/* We saw the whole header, let's check if the body is done as well */
+				if (content_size && bytes_read >= header_size + content_size)
+					break;
+			} else {
+				/* Did we see the header end? Then get the body size. */
+				eoh = memmem (buffer, bytes_read, "\r\n\r\n", 4);
+				if (eoh) {
+					char *header = find_header (buffer, "Content-Length: ");
+
+					header_size = eoh - buffer + 4;
+					if (header)
+						content_size = atoi(header);
+				}
+			}
 
 			if (bytes_read == BUFSZ - 1) {
 				log_warn("Response too big\n");
@@ -111,7 +127,7 @@ int http_receive(struct tunnel *tunnel, char **response)
 		}
 	} while (n >= 0);
 
-	if (n < 0) {
+	if (!header_size) {
 		log_debug("Error reading from SSL connection (%s).\n",
 			  err_ssl_str(n));
 		free(buffer);