http: always consume body on auth failure

When we get an authentication failure, we must consume the entire body
of the response.  If we only read half of the body (on the assumption
that we can ignore the rest) then we will never complete the parsing of
the message.  This means that we will never set the complete flag, and
our replay must actually tear down the connection and try again.

This is particularly problematic for stateful authentication mechanisms
(SPNEGO, NTLM) that require that we keep the connection alive.

Note that the prior code is only a problem when the 401 that we are
parsing is too large to be read in a single chunked read from the http
parser.

But now we will continue to invoke the http parser until we've got a
complete message in the authentication failed scenario.  Note that we
need not do anything with the message, so when we get an authentication
failed, we'll stop adding data to our buffer, we'll simply loop in the
parser and let it advance its internal state.

src/transports/http.c

@@ -582,13 +582,6 @@ static int on_body_fill_buffer(http_parser *parser, const char *str, size_t len)
 	parser_context *ctx = (parser_context *) parser->data;
 	http_subtransport *t = ctx->t;
 
-	/* If our goal is to replay the request (either an auth failure or
-	 * a redirect) then don't bother buffering since we're ignoring the
-	 * content anyway.
-	 */
-	if (t->parse_error == PARSE_ERROR_REPLAY)
-		return 0;
-
 	/* If there's no buffer set, we're explicitly ignoring the body. */
 	if (ctx->buffer) {
 		if (ctx->buf_size < len) {
@@ -1018,10 +1011,12 @@ static int http_stream_read(
 	parser_context ctx;
 	size_t bytes_parsed;
 	git_buf request = GIT_BUF_INIT;
+	bool auth_replay;
 	int error = 0;
 
 replay:
 	*bytes_read = 0;
+	auth_replay = false;
 
 	assert(t->connected);
 
@@ -1078,15 +1073,18 @@ replay:
 		if ((error = gitno_recv(&t->parse_buffer)) < 0)
 			goto done;
 
-		/* This call to http_parser_execute will result in invocations of the
-		 * on_* family of callbacks. The most interesting of these is
-		 * on_body_fill_buffer, which is called when data is ready to be copied
-		 * into the target buffer. We need to marshal the buffer, buf_size, and
-		 * bytes_read parameters to this callback. */
+		/*
+		 * This call to http_parser_execute will result in invocations
+		 * of the on_* family of callbacks, including on_body_fill_buffer
+		 * which will write into the target buffer.  Set up the buffer
+		 * for it to write into _unless_ we got an auth failure; in
+		 * that case we only care about the headers and don't need to
+		 * bother copying the body.
+		 */
 		ctx.t = t;
 		ctx.s = s;
-		ctx.buffer = buffer;
-		ctx.buf_size = buf_size;
+		ctx.buffer = auth_replay ? NULL : buffer;
+		ctx.buf_size = auth_replay ? 0 : buf_size;
 		ctx.bytes_read = bytes_read;
 
 		/* Set the context, call the parser, then unset the context. */
@@ -1099,18 +1097,10 @@ replay:
 
 		t->parser.data = NULL;
 
-		/* If there was a handled authentication failure, then parse_error
-		 * will have signaled us that we should replay the request. */
-		if (PARSE_ERROR_REPLAY == t->parse_error) {
-			s->sent_request = 0;
-
-			if ((error = http_connect(t)) < 0)
-				goto done;
-
-			goto replay;
-		}
-
-		if (t->parse_error == PARSE_ERROR_EXT) {
+		/* On a 401, read the rest of the response then retry. */
+		if (t->parse_error == PARSE_ERROR_REPLAY) {
+			auth_replay = true;
+		} else if (t->parse_error == PARSE_ERROR_EXT) {
 			error = t->error;
 			goto done;
 		} else if (t->parse_error < 0) {
@@ -1127,6 +1117,15 @@ replay:
 		}
 	}
 
+	if (auth_replay) {
+		s->sent_request = 0;
+
+		if ((error = http_connect(t)) < 0)
+			return error;
+
+		goto replay;
+	}
+
 done:
 	git_buf_dispose(&request);
 	return error;