From f4113cac0c88b4f36ee6f3abf3218034440a68e3 Mon Sep 17 00:00:00 2001 From: Blake Burkhart Date: Tue, 22 Sep 2015 18:06:04 -0400 Subject: [PATCH] http: limit redirection to protocol-whitelist Previously, libcurl would follow redirection to any protocol it was compiled for support with. This is desirable to allow redirection from HTTP to HTTPS. However, it would even successfully allow redirection from HTTP to SFTP, a protocol that git does not otherwise support at all. Furthermore git's new protocol-whitelisting could be bypassed by following a redirect within the remote helper, as it was only enforced at transport selection time. This patch limits redirects within libcurl to HTTP, HTTPS, FTP and FTPS. If there is a protocol-whitelist present, this list is limited to those also allowed by the whitelist. As redirection happens from within libcurl, it is impossible for an HTTP redirect to a protocol implemented within another remote helper. When the curl version git was compiled with is too old to support restrictions on protocol redirection, we warn the user if GIT_ALLOW_PROTOCOL restrictions were requested. This is a little inaccurate, as even without that variable in the environment, we would still restrict SFTP, etc, and we do not warn in that case. But anything else means we would literally warn every time git accesses an http remote. This commit includes a test, but it is not as robust as we would hope. It redirects an http request to ftp, and checks that curl complained about the protocol, which means that we are relying on curl's specific error message to know what happened. Ideally we would redirect to a working ftp server and confirm that we can clone without protocol restrictions, and not with them. But we do not have a portable way of providing an ftp server, nor any other protocol that curl supports (https is the closest, but we would have to deal with certificates). [jk: added test and version warning] Signed-off-by: Jeff King Signed-off-by: Junio C Hamano Upstream-Status: Backport https://kernel.googlesource.com/pub/scm/git/git/+/f4113cac0c88b4f36ee6f3abf3218034440a68e3%5E%21/ CVE: CVE-2015-7545 patch #1 Signed-off-by: Armin Kuster --- Documentation/git.txt | 5 ----- http.c | 17 +++++++++++++++++ t/lib-httpd/apache.conf | 1 + t/t5812-proto-disable-http.sh | 9 +++++++++ 4 files changed, 27 insertions(+), 5 deletions(-) Index: git-2.3.0/Documentation/git.txt =================================================================== --- git-2.3.0.orig/Documentation/git.txt +++ git-2.3.0/Documentation/git.txt @@ -1049,11 +1049,6 @@ GIT_ICASE_PATHSPECS:: - any external helpers are named by their protocol (e.g., use `hg` to allow the `git-remote-hg` helper) -+ -Note that this controls only git's internal protocol selection. -If libcurl is used (e.g., by the `http` transport), it may -redirect to other protocols. There is not currently any way to -restrict this. Discussion[[Discussion]] Index: git-2.3.0/http.c =================================================================== --- git-2.3.0.orig/http.c +++ git-2.3.0/http.c @@ -8,6 +8,7 @@ #include "credential.h" #include "version.h" #include "pkt-line.h" +#include "transport.h" int active_requests; int http_is_verbose; @@ -300,6 +301,7 @@ static void set_curl_keepalive(CURL *c) static CURL *get_curl_handle(void) { CURL *result = curl_easy_init(); + long allowed_protocols = 0; if (!result) die("curl_easy_init failed"); @@ -352,6 +354,21 @@ static CURL *get_curl_handle(void) #elif LIBCURL_VERSION_NUM >= 0x071101 curl_easy_setopt(result, CURLOPT_POST301, 1); #endif +#if LIBCURL_VERSION_NUM >= 0x071304 + if (is_transport_allowed("http")) + allowed_protocols |= CURLPROTO_HTTP; + if (is_transport_allowed("https")) + allowed_protocols |= CURLPROTO_HTTPS; + if (is_transport_allowed("ftp")) + allowed_protocols |= CURLPROTO_FTP; + if (is_transport_allowed("ftps")) + allowed_protocols |= CURLPROTO_FTPS; + curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS, allowed_protocols); +#else + if (transport_restrict_protocols()) + warning("protocol restrictions not applied to curl redirects because\n" + "your curl version is too old (>= 7.19.4)"); +#endif if (getenv("GIT_CURL_VERBOSE")) curl_easy_setopt(result, CURLOPT_VERBOSE, 1); Index: git-2.3.0/t/lib-httpd/apache.conf =================================================================== --- git-2.3.0.orig/t/lib-httpd/apache.conf +++ git-2.3.0/t/lib-httpd/apache.conf @@ -118,6 +118,7 @@ RewriteRule ^/smart-redir-perm/(.*)$ /sm RewriteRule ^/smart-redir-temp/(.*)$ /smart/$1 [R=302] RewriteRule ^/smart-redir-auth/(.*)$ /auth/smart/$1 [R=301] RewriteRule ^/smart-redir-limited/(.*)/info/refs$ /smart/$1/info/refs [R=301] +RewriteRule ^/ftp-redir/(.*)$ ftp://localhost:1000/$1 [R=302] LoadModule ssl_module modules/mod_ssl.so Index: git-2.3.0/t/t5812-proto-disable-http.sh =================================================================== --- git-2.3.0.orig/t/t5812-proto-disable-http.sh +++ git-2.3.0/t/t5812-proto-disable-http.sh @@ -16,5 +16,14 @@ test_expect_success 'create git-accessib test_proto "smart http" http "$HTTPD_URL/smart/repo.git" +test_expect_success 'curl redirects respect whitelist' ' + test_must_fail env GIT_ALLOW_PROTOCOL=http:https \ + git clone "$HTTPD_URL/ftp-redir/repo.git" 2>stderr && + { + test_i18ngrep "ftp.*disabled" stderr || + test_i18ngrep "your curl version is too old" + } +' + stop_httpd test_done