Another memory overrun in http-push.c

From: Eygene Ryabinkin <rea-git@codelabs.ru>
Date: Mar 1, 2007, 16:09 UTC
Message-ID: <20070301160911.GU57456@codelabs.ru>

Me again ;))

Spotted another memory overrun in the http-push.c. In principle, it is the read-only overrun, but it provokes the coredump on my system. The problem is that strlcpy(dst, src, size) returns the length of the 'src' and demands it to be NULL-terminated (see 'man strlcpy' and http://www.gratisoft.us/todd/papers/strlcpy.html). It is not the case for the xml_cdata and possibly other places. So I've just replaced strlcpy with memcpy + zero termination all over the http-push.c. The patch is below.

--- http-push.c.orig Thu Mar 1 18:48:19 2007 +++ http-push.c Thu Mar 1 18:55:24 2007

@@ -1271,7 +1271,9 @@
 	struct xml_ctx *ctx = (struct xml_ctx *)userData;
 	free(ctx->cdata);
 	ctx->cdata = xmalloc(len + 1);
-	strlcpy(ctx->cdata, s, len + 1);
+	/* NB: 's' is not null-terminated, can not use strlcpy here */
+	memcpy(ctx->cdata, s, len);
+	ctx->cdata[len] = '\0';
 }
 
 static struct remote_lock *lock_remote(const char *path, long timeout)
@@ -1473,7 +1475,8 @@
 		return;
 	path += 8;
 	obj_hex = xmalloc(strlen(path));
-	strlcpy(obj_hex, path, 3);
+	/* NB: path is not null-terminated, can not use strlcpy here */
+	memcpy(obj_hex, path, 2);
 	strcpy(obj_hex + 2, path + 3);
 	one_remote_object(obj_hex);
 	free(obj_hex);
@@ -2170,7 +2173,8 @@
 	/* If it's a symref, set the refname; otherwise try for a sha1 */
 	if (!strncmp((char *)buffer.buffer, "ref: ", 5)) {
 		*symref = xmalloc(buffer.posn - 5);
-		strlcpy(*symref, (char *)buffer.buffer + 5, buffer.posn - 5);
+		memcpy(*symref, (char *)buffer.buffer + 5, buffer.posn - 6);
+		(*symref)[buffer.posn - 6] = '\0';
 	} else {
 		get_sha1_hex(buffer.buffer, sha1);
 	}

memcpy(obj_hex, path, 2) is not followed by zero-termination since
it will be done by the strcpy that is following.

This cured my git-http-push and let it do all PROPFINDS on the rather
large repository (175 Mb). Now I have only one SEGV that is happening
inside the libcurl both in http-push.c and http-fetch.c. Already
talking to CURL people and trying to write the clear testcase for
the problem.

-- 
Eygene