summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorJeff King <peff@peff.net>2015-09-16 17:12:52 (GMT)
committerJunio C Hamano <gitster@pobox.com>2015-09-23 18:35:48 (GMT)
commita5adaced2e13c135d5d9cc65be9eb95aa3bacedf (patch)
treee4ad0544170f80c65ee073d08d2974780be5d5df
parentecad27cf98c391d5cfdc26ce0e442e02347baad0 (diff)
downloadgit-a5adaced2e13c135d5d9cc65be9eb95aa3bacedf.zip
git-a5adaced2e13c135d5d9cc65be9eb95aa3bacedf.tar.gz
git-a5adaced2e13c135d5d9cc65be9eb95aa3bacedf.tar.bz2
transport: add a protocol-whitelist environment variable
If we are cloning an untrusted remote repository into a sandbox, we may also want to fetch remote submodules in order to get the complete view as intended by the other side. However, that opens us up to attacks where a malicious user gets us to clone something they would not otherwise have access to (this is not necessarily a problem by itself, but we may then act on the cloned contents in a way that exposes them to the attacker). Ideally such a setup would sandbox git entirely away from high-value items, but this is not always practical or easy to set up (e.g., OS network controls may block multiple protocols, and we would want to enable some but not others). We can help this case by providing a way to restrict particular protocols. We use a whitelist in the environment. This is more annoying to set up than a blacklist, but defaults to safety if the set of protocols git supports grows). If no whitelist is specified, we continue to default to allowing all protocols (this is an "unsafe" default, but since the minority of users will want this sandboxing effect, it is the only sensible one). A note on the tests: ideally these would all be in a single test file, but the git-daemon and httpd test infrastructure is an all-or-nothing proposition rather than a test-by-test prerequisite. By putting them all together, we would be unable to test the file-local code on machines without apache. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--Documentation/git.txt32
-rw-r--r--connect.c5
-rw-r--r--t/lib-proto-disable.sh96
-rwxr-xr-xt/t5810-proto-disable-local.sh14
-rwxr-xr-xt/t5811-proto-disable-git.sh20
-rwxr-xr-xt/t5812-proto-disable-http.sh20
-rwxr-xr-xt/t5813-proto-disable-ssh.sh20
-rwxr-xr-xt/t5814-proto-disable-ext.sh18
-rw-r--r--transport-helper.c2
-rw-r--r--transport.c21
-rw-r--r--transport.h7
11 files changed, 254 insertions, 1 deletions
diff --git a/Documentation/git.txt b/Documentation/git.txt
index a62ed6f..b6a12b3 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -1045,6 +1045,38 @@ GIT_ICASE_PATHSPECS::
an operation has touched every ref (e.g., because you are
cloning a repository to make a backup).
+`GIT_ALLOW_PROTOCOL`::
+ If set, provide a colon-separated list of protocols which are
+ allowed to be used with fetch/push/clone. This is useful to
+ restrict recursive submodule initialization from an untrusted
+ repository. Any protocol not mentioned will be disallowed (i.e.,
+ this is a whitelist, not a blacklist). If the variable is not
+ set at all, all protocols are enabled. The protocol names
+ currently used by git are:
+
+ - `file`: any local file-based path (including `file://` URLs,
+ or local paths)
+
+ - `git`: the anonymous git protocol over a direct TCP
+ connection (or proxy, if configured)
+
+ - `ssh`: git over ssh (including `host:path` syntax,
+ `git+ssh://`, etc).
+
+ - `rsync`: git over rsync
+
+ - `http`: git over http, both "smart http" and "dumb http".
+ Note that this does _not_ include `https`; if you want both,
+ you should specify both as `http:https`.
+
+ - 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]]
------------------------
diff --git a/connect.c b/connect.c
index 14c924b..bd4b50e 100644
--- a/connect.c
+++ b/connect.c
@@ -9,6 +9,7 @@
#include "url.h"
#include "string-list.h"
#include "sha1-array.h"
+#include "transport.h"
static char *server_capabilities;
static const char *parse_feature_value(const char *, const char *, int *);
@@ -694,6 +695,8 @@ struct child_process *git_connect(int fd[2], const char *url,
else
target_host = xstrdup(hostandport);
+ transport_check_allowed("git");
+
/* These underlying connection commands die() if they
* cannot connect.
*/
@@ -727,6 +730,7 @@ struct child_process *git_connect(int fd[2], const char *url,
int putty;
char *ssh_host = hostandport;
const char *port = NULL;
+ transport_check_allowed("ssh");
get_host_and_port(&ssh_host, &port);
if (!port)
@@ -768,6 +772,7 @@ struct child_process *git_connect(int fd[2], const char *url,
/* remove repo-local variables from the environment */
conn->env = local_repo_env;
conn->use_shell = 1;
+ transport_check_allowed("file");
}
argv_array_push(&conn->args, cmd.buf);
diff --git a/t/lib-proto-disable.sh b/t/lib-proto-disable.sh
new file mode 100644
index 0000000..b0917d9
--- /dev/null
+++ b/t/lib-proto-disable.sh
@@ -0,0 +1,96 @@
+# Test routines for checking protocol disabling.
+
+# test cloning a particular protocol
+# $1 - description of the protocol
+# $2 - machine-readable name of the protocol
+# $3 - the URL to try cloning
+test_proto () {
+ desc=$1
+ proto=$2
+ url=$3
+
+ test_expect_success "clone $1 (enabled)" '
+ rm -rf tmp.git &&
+ (
+ GIT_ALLOW_PROTOCOL=$proto &&
+ export GIT_ALLOW_PROTOCOL &&
+ git clone --bare "$url" tmp.git
+ )
+ '
+
+ test_expect_success "fetch $1 (enabled)" '
+ (
+ cd tmp.git &&
+ GIT_ALLOW_PROTOCOL=$proto &&
+ export GIT_ALLOW_PROTOCOL &&
+ git fetch
+ )
+ '
+
+ test_expect_success "push $1 (enabled)" '
+ (
+ cd tmp.git &&
+ GIT_ALLOW_PROTOCOL=$proto &&
+ export GIT_ALLOW_PROTOCOL &&
+ git push origin HEAD:pushed
+ )
+ '
+
+ test_expect_success "push $1 (disabled)" '
+ (
+ cd tmp.git &&
+ GIT_ALLOW_PROTOCOL=none &&
+ export GIT_ALLOW_PROTOCOL &&
+ test_must_fail git push origin HEAD:pushed
+ )
+ '
+
+ test_expect_success "fetch $1 (disabled)" '
+ (
+ cd tmp.git &&
+ GIT_ALLOW_PROTOCOL=none &&
+ export GIT_ALLOW_PROTOCOL &&
+ test_must_fail git fetch
+ )
+ '
+
+ test_expect_success "clone $1 (disabled)" '
+ rm -rf tmp.git &&
+ (
+ GIT_ALLOW_PROTOCOL=none &&
+ export GIT_ALLOW_PROTOCOL &&
+ test_must_fail git clone --bare "$url" tmp.git
+ )
+ '
+}
+
+# set up an ssh wrapper that will access $host/$repo in the
+# trash directory, and enable it for subsequent tests.
+setup_ssh_wrapper () {
+ test_expect_success 'setup ssh wrapper' '
+ write_script ssh-wrapper <<-\EOF &&
+ echo >&2 "ssh: $*"
+ host=$1; shift
+ cd "$TRASH_DIRECTORY/$host" &&
+ eval "$*"
+ EOF
+ GIT_SSH="$PWD/ssh-wrapper" &&
+ export GIT_SSH &&
+ export TRASH_DIRECTORY
+ '
+}
+
+# set up a wrapper that can be used with remote-ext to
+# access repositories in the "remote" directory of trash-dir,
+# like "ext::fake-remote %S repo.git"
+setup_ext_wrapper () {
+ test_expect_success 'setup ext wrapper' '
+ write_script fake-remote <<-\EOF &&
+ echo >&2 "fake-remote: $*"
+ cd "$TRASH_DIRECTORY/remote" &&
+ eval "$*"
+ EOF
+ PATH=$TRASH_DIRECTORY:$PATH &&
+ export TRASH_DIRECTORY
+ '
+}
diff --git a/t/t5810-proto-disable-local.sh b/t/t5810-proto-disable-local.sh
new file mode 100755
index 0000000..563592d
--- /dev/null
+++ b/t/t5810-proto-disable-local.sh
@@ -0,0 +1,14 @@
+#!/bin/sh
+
+test_description='test disabling of local paths in clone/fetch'
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-proto-disable.sh"
+
+test_expect_success 'setup repository to clone' '
+ test_commit one
+'
+
+test_proto "file://" file "file://$PWD"
+test_proto "path" file .
+
+test_done
diff --git a/t/t5811-proto-disable-git.sh b/t/t5811-proto-disable-git.sh
new file mode 100755
index 0000000..8ac6b2a
--- /dev/null
+++ b/t/t5811-proto-disable-git.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+
+test_description='test disabling of git-over-tcp in clone/fetch'
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-proto-disable.sh"
+. "$TEST_DIRECTORY/lib-git-daemon.sh"
+start_git_daemon
+
+test_expect_success 'create git-accessible repo' '
+ bare="$GIT_DAEMON_DOCUMENT_ROOT_PATH/repo.git" &&
+ test_commit one &&
+ git --bare init "$bare" &&
+ git push "$bare" HEAD &&
+ >"$bare/git-daemon-export-ok" &&
+ git -C "$bare" config daemon.receivepack true
+'
+
+test_proto "git://" git "$GIT_DAEMON_URL/repo.git"
+
+test_done
diff --git a/t/t5812-proto-disable-http.sh b/t/t5812-proto-disable-http.sh
new file mode 100755
index 0000000..dd5001c
--- /dev/null
+++ b/t/t5812-proto-disable-http.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+
+test_description='test disabling of git-over-http in clone/fetch'
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-proto-disable.sh"
+. "$TEST_DIRECTORY/lib-httpd.sh"
+start_httpd
+
+test_expect_success 'create git-accessible repo' '
+ bare="$HTTPD_DOCUMENT_ROOT_PATH/repo.git" &&
+ test_commit one &&
+ git --bare init "$bare" &&
+ git push "$bare" HEAD &&
+ git -C "$bare" config http.receivepack true
+'
+
+test_proto "smart http" http "$HTTPD_URL/smart/repo.git"
+
+stop_httpd
+test_done
diff --git a/t/t5813-proto-disable-ssh.sh b/t/t5813-proto-disable-ssh.sh
new file mode 100755
index 0000000..ad877d7
--- /dev/null
+++ b/t/t5813-proto-disable-ssh.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+
+test_description='test disabling of git-over-ssh in clone/fetch'
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-proto-disable.sh"
+
+setup_ssh_wrapper
+
+test_expect_success 'setup repository to clone' '
+ test_commit one &&
+ mkdir remote &&
+ git init --bare remote/repo.git &&
+ git push remote/repo.git HEAD
+'
+
+test_proto "host:path" ssh "remote:repo.git"
+test_proto "ssh://" ssh "ssh://remote/$PWD/remote/repo.git"
+test_proto "git+ssh://" ssh "git+ssh://remote/$PWD/remote/repo.git"
+
+test_done
diff --git a/t/t5814-proto-disable-ext.sh b/t/t5814-proto-disable-ext.sh
new file mode 100755
index 0000000..9d6f7df
--- /dev/null
+++ b/t/t5814-proto-disable-ext.sh
@@ -0,0 +1,18 @@
+#!/bin/sh
+
+test_description='test disabling of remote-helper paths in clone/fetch'
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-proto-disable.sh"
+
+setup_ext_wrapper
+
+test_expect_success 'setup repository to clone' '
+ test_commit one &&
+ mkdir remote &&
+ git init --bare remote/repo.git &&
+ git push remote/repo.git HEAD
+'
+
+test_proto "remote-helper" ext "ext::fake-remote %S repo.git"
+
+test_done
diff --git a/transport-helper.c b/transport-helper.c
index 7dc4a44..0b5362c 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -1038,6 +1038,8 @@ int transport_helper_init(struct transport *transport, const char *name)
struct helper_data *data = xcalloc(1, sizeof(*data));
data->name = name;
+ transport_check_allowed(name);
+
if (getenv("GIT_TRANSPORT_HELPER_DEBUG"))
debug = 1;
diff --git a/transport.c b/transport.c
index 88bde1d..94fe865 100644
--- a/transport.c
+++ b/transport.c
@@ -909,6 +909,20 @@ static int external_specification_len(const char *url)
return strchr(url, ':') - url;
}
+void transport_check_allowed(const char *type)
+{
+ struct string_list allowed = STRING_LIST_INIT_DUP;
+ const char *v = getenv("GIT_ALLOW_PROTOCOL");
+
+ if (!v)
+ return;
+
+ string_list_split(&allowed, v, ':', -1);
+ if (!unsorted_string_list_has_string(&allowed, type))
+ die("transport '%s' not allowed", type);
+ string_list_clear(&allowed, 0);
+}
+
struct transport *transport_get(struct remote *remote, const char *url)
{
const char *helper;
@@ -940,12 +954,14 @@ struct transport *transport_get(struct remote *remote, const char *url)
if (helper) {
transport_helper_init(ret, helper);
} else if (starts_with(url, "rsync:")) {
+ transport_check_allowed("rsync");
ret->get_refs_list = get_refs_via_rsync;
ret->fetch = fetch_objs_via_rsync;
ret->push = rsync_transport_push;
ret->smart_options = NULL;
} else if (url_is_local_not_ssh(url) && is_file(url) && is_bundle(url, 1)) {
struct bundle_transport_data *data = xcalloc(1, sizeof(*data));
+ transport_check_allowed("file");
ret->data = data;
ret->get_refs_list = get_refs_from_bundle;
ret->fetch = fetch_refs_from_bundle;
@@ -957,7 +973,10 @@ struct transport *transport_get(struct remote *remote, const char *url)
|| starts_with(url, "ssh://")
|| starts_with(url, "git+ssh://")
|| starts_with(url, "ssh+git://")) {
- /* These are builtin smart transports. */
+ /*
+ * These are builtin smart transports; "allowed" transports
+ * will be checked individually in git_connect.
+ */
struct git_transport_data *data = xcalloc(1, sizeof(*data));
ret->data = data;
ret->set_option = NULL;
diff --git a/transport.h b/transport.h
index 3e0091e..f7df6ec 100644
--- a/transport.h
+++ b/transport.h
@@ -132,6 +132,13 @@ struct transport {
/* Returns a transport suitable for the url */
struct transport *transport_get(struct remote *, const char *);
+/*
+ * Check whether a transport is allowed by the environment,
+ * and die otherwise. type should generally be the URL scheme,
+ * as described in Documentation/git.txt
+ */
+void transport_check_allowed(const char *type);
+
/* Transport options which apply to git:// and scp-style URLs */
/* The program to use on the remote side to send a pack */