Re: segfault in http.c when https URL is mistyped

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On Wed, Sep 07, 2016 at 03:44:04PM +0200, Lars Wendler wrote:

> we at Gentoo got a bug report [1] about git-remote-https segfaulting
> when the URL has been mistyped. 
> This seems to only be triggered when git was compiled with curl
> support:
> 
>   git clone https::/some.example-site.net/test.git

Thanks, this was easy to reproduce. It's a regression in v2.8.0. The fix
is below.

-- >8 --
Subject: [PATCH] remote-curl: handle URLs without protocol

Generally remote-curl would never see a URL that did not
have "proto:" at the beginning, as that is what tells git to
run the "git-remote-proto" helper (and git-remote-http, etc,
are aliases for git-remote-curl).

However, the special syntax "proto::something" will run
git-remote-proto with only "something" as the URL. So a
malformed URL like:

  http::/example.com/repo.git

will feed the URL "/example.com/repo.git" to
git-remote-http. The resulting URL has no protocol, but the
code added by 372370f (http: use credential API to handle
proxy authentication, 2016-01-26) does not handle this case
and segfaults.

For the purposes of this code, we don't really care what the
exact protocol; only whether or not it is https. So let's
just assume that a missing protocol is not, and curl will
handle the real error (which is that the URL is nonsense).

Signed-off-by: Jeff King <peff@xxxxxxxx>
---
I looked around for other similar over-assumptions about the URL parsing
but didn't see any.

 http.c                     | 2 +-
 t/t5550-http-fetch-dumb.sh | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/http.c b/http.c
index cd40b01..edce47c 100644
--- a/http.c
+++ b/http.c
@@ -723,7 +723,7 @@ static CURL *get_curl_handle(void)
 	 * precedence here, as in CURL.
 	 */
 	if (!curl_http_proxy) {
-		if (!strcmp(http_auth.protocol, "https")) {
+		if (http_auth.protocol && !strcmp(http_auth.protocol, "https")) {
 			var_override(&curl_http_proxy, getenv("HTTPS_PROXY"));
 			var_override(&curl_http_proxy, getenv("https_proxy"));
 		} else {
diff --git a/t/t5550-http-fetch-dumb.sh b/t/t5550-http-fetch-dumb.sh
index 3484b6f..01bb633 100755
--- a/t/t5550-http-fetch-dumb.sh
+++ b/t/t5550-http-fetch-dumb.sh
@@ -299,5 +299,13 @@ test_expect_success 'git client does not send an empty Accept-Language' '
 	! grep "^Accept-Language:" stderr
 '
 
+test_expect_success 'remote-http complains cleanly about malformed urls' '
+	# do not actually issue "list" or other commands, as we do not
+	# want to rely on what curl would actually do with such a broken
+	# URL. This is just about making sure we do not segfault during
+	# initialization.
+	test_must_fail git remote-http http::/example.com/repo.git
+'
+
 stop_httpd
 test_done
-- 
2.10.0.rc2.154.gb4a4b8b




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