From 9f21141ed73a5abba0cd2ce944eacbb77df55cf4 Mon Sep 17 00:00:00 2001 From: Petr Stodulka Date: Oct 28 2015 16:50:58 +0000 Subject: fix arbitrary code execution via crafted URLs Resolves: #1269797 --- diff --git a/0001-transport-add-a-protocol-whitelist-environment-varia.patch b/0001-transport-add-a-protocol-whitelist-environment-varia.patch new file mode 100644 index 0000000..9db8867 --- /dev/null +++ b/0001-transport-add-a-protocol-whitelist-environment-varia.patch @@ -0,0 +1,207 @@ +From 0730270cd672467c12a3f3bf36336d169700269a Mon Sep 17 00:00:00 2001 +From: Petr Stodulka +Date: Wed, 28 Oct 2015 17:22:13 +0100 +Subject: [PATCH 1/5] 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. +--- + Documentation/git.txt | 31 +++++++++++++++++++++++++++++++ + connect.c | 5 +++++ + transport-helper.c | 2 ++ + transport.c | 21 ++++++++++++++++++++- + transport.h | 7 +++++++ + 5 files changed, 65 insertions(+), 1 deletion(-) + +diff --git a/Documentation/git.txt b/Documentation/git.txt +index f4cb5cb..71ba92b 100644 +--- a/Documentation/git.txt ++++ b/Documentation/git.txt +@@ -1069,6 +1069,37 @@ 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 c0144d8..27a706f 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, tortoiseplink = 0; + char *ssh_host = hostandport; + const char *port = NULL; ++ transport_check_allowed("ssh"); + get_host_and_port(&ssh_host, &port); + + if (!port) +@@ -781,6 +785,7 @@ 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/transport-helper.c b/transport-helper.c +index 5d99a6b..b486441 100644 +--- a/transport-helper.c ++++ b/transport-helper.c +@@ -1039,6 +1039,8 @@ 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 40692f8..ad1ae7f 100644 +--- a/transport.c ++++ b/transport.c +@@ -912,6 +912,20 @@ 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; +@@ -943,12 +957,14 @@ 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; +@@ -960,7 +976,10 @@ 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 18d2cf8..742027f 100644 +--- a/transport.h ++++ b/transport.h +@@ -133,6 +133,13 @@ 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 */ +-- +2.1.0 + diff --git a/0002-submodule-allow-only-certain-protocols-for-submodule.patch b/0002-submodule-allow-only-certain-protocols-for-submodule.patch new file mode 100644 index 0000000..dc9dcef --- /dev/null +++ b/0002-submodule-allow-only-certain-protocols-for-submodule.patch @@ -0,0 +1,108 @@ +From 772390a8977b0c667aefe0ba4989d4f36f3d1832 Mon Sep 17 00:00:00 2001 +From: Jeff King +Date: Wed, 16 Sep 2015 13:13:12 -0400 +Subject: [PATCH 2/5] submodule: allow only certain protocols for submodule + fetches + +Some protocols (like git-remote-ext) can execute arbitrary +code found in the URL. The URLs that submodules use may come +from arbitrary sources (e.g., .gitmodules files in a remote +repository). Let's restrict submodules to fetching from a +known-good subset of protocols. + +Note that we apply this restriction to all submodule +commands, whether the URL comes from .gitmodules or not. +This is more restrictive than we need to be; for example, in +the tests we run: + + git submodule add ext::... + +which should be trusted, as the URL comes directly from the +command line provided by the user. But doing it this way is +simpler, and makes it much less likely that we would miss a +case. And since such protocols should be an exception +(especially because nobody who clones from them will be able +to update the submodules!), it's not likely to inconvenience +anyone in practice. + +Reported-by: Blake Burkhart +Signed-off-by: Jeff King +Signed-off-by: Junio C Hamano +--- + git-submodule.sh | 9 +++++++++ + t/t5815-submodule-protos.sh | 43 +++++++++++++++++++++++++++++++++++++++++++ + 2 files changed, 52 insertions(+) + create mode 100755 t/t5815-submodule-protos.sh + +diff --git a/git-submodule.sh b/git-submodule.sh +index 36797c3..78c2740 100755 +--- a/git-submodule.sh ++++ b/git-submodule.sh +@@ -22,6 +22,15 @@ require_work_tree + wt_prefix=$(git rev-parse --show-prefix) + cd_to_toplevel + ++# Restrict ourselves to a vanilla subset of protocols; the URLs ++# we get are under control of a remote repository, and we do not ++# want them kicking off arbitrary git-remote-* programs. ++# ++# If the user has already specified a set of allowed protocols, ++# we assume they know what they're doing and use that instead. ++: ${GIT_ALLOW_PROTOCOL=file:git:http:https:ssh} ++export GIT_ALLOW_PROTOCOL ++ + command= + branch= + force= +diff --git a/t/t5815-submodule-protos.sh b/t/t5815-submodule-protos.sh +new file mode 100755 +index 0000000..06f55a1 +--- /dev/null ++++ b/t/t5815-submodule-protos.sh +@@ -0,0 +1,43 @@ ++#!/bin/sh ++ ++test_description='test protocol whitelisting with submodules' ++. ./test-lib.sh ++. "$TEST_DIRECTORY"/lib-proto-disable.sh ++ ++setup_ext_wrapper ++setup_ssh_wrapper ++ ++test_expect_success 'setup repository with submodules' ' ++ mkdir remote && ++ git init remote/repo.git && ++ (cd remote/repo.git && test_commit one) && ++ # submodule-add should probably trust what we feed it on the cmdline, ++ # but its implementation is overly conservative. ++ GIT_ALLOW_PROTOCOL=ssh git submodule add remote:repo.git ssh-module && ++ GIT_ALLOW_PROTOCOL=ext git submodule add "ext::fake-remote %S repo.git" ext-module && ++ git commit -m "add submodules" ++' ++ ++test_expect_success 'clone with recurse-submodules fails' ' ++ test_must_fail git clone --recurse-submodules . dst ++' ++ ++test_expect_success 'setup individual updates' ' ++ rm -rf dst && ++ git clone . dst && ++ git -C dst submodule init ++' ++ ++test_expect_success 'update of ssh allowed' ' ++ git -C dst submodule update ssh-module ++' ++ ++test_expect_success 'update of ext not allowed' ' ++ test_must_fail git -C dst submodule update ext-module ++' ++ ++test_expect_success 'user can override whitelist' ' ++ GIT_ALLOW_PROTOCOL=ext git -C dst submodule update ext-module ++' ++ ++test_done +-- +2.1.0 + diff --git a/0003-transport-refactor-protocol-whitelist-code.patch b/0003-transport-refactor-protocol-whitelist-code.patch new file mode 100644 index 0000000..71fbbad --- /dev/null +++ b/0003-transport-refactor-protocol-whitelist-code.patch @@ -0,0 +1,107 @@ +From 92773f7741ead61f9bdbdaf28272cca405da4fd7 Mon Sep 17 00:00:00 2001 +From: Jeff King +Date: Tue, 22 Sep 2015 18:03:49 -0400 +Subject: [PATCH 3/5] transport: refactor protocol whitelist code + +The current callers only want to die when their transport is +prohibited. But future callers want to query the mechanism +without dying. + +Let's break out a few query functions, and also save the +results in a static list so we don't have to re-parse for +each query. + +Based-on-a-patch-by: Blake Burkhart +Signed-off-by: Jeff King +Signed-off-by: Junio C Hamano +--- + transport.c | 38 ++++++++++++++++++++++++++++++-------- + transport.h | 15 +++++++++++++-- + 2 files changed, 43 insertions(+), 10 deletions(-) + +diff --git a/transport.c b/transport.c +index ad1ae7f..164a716 100644 +--- a/transport.c ++++ b/transport.c +@@ -912,18 +912,40 @@ static int external_specification_len(const char *url) + return strchr(url, ':') - url; + } + +-void transport_check_allowed(const char *type) ++static const struct string_list *protocol_whitelist(void) + { +- struct string_list allowed = STRING_LIST_INIT_DUP; +- const char *v = getenv("GIT_ALLOW_PROTOCOL"); ++ static int enabled = -1; ++ static struct string_list allowed = STRING_LIST_INIT_DUP; ++ ++ if (enabled < 0) { ++ const char *v = getenv("GIT_ALLOW_PROTOCOL"); ++ if (v) { ++ string_list_split(&allowed, v, ':', -1); ++ string_list_sort(&allowed); ++ enabled = 1; ++ } else { ++ enabled = 0; ++ } ++ } + +- if (!v) +- return; ++ return enabled ? &allowed : NULL; ++} ++ ++int is_transport_allowed(const char *type) ++{ ++ const struct string_list *allowed = protocol_whitelist(); ++ return !allowed || string_list_has_string(allowed, type); ++} + +- string_list_split(&allowed, v, ':', -1); +- if (!unsorted_string_list_has_string(&allowed, type)) ++void transport_check_allowed(const char *type) ++{ ++ if (!is_transport_allowed(type)) + die("transport '%s' not allowed", type); +- string_list_clear(&allowed, 0); ++} ++ ++int transport_restrict_protocols(void) ++{ ++ return !!protocol_whitelist(); + } + + struct transport *transport_get(struct remote *remote, const char *url) +diff --git a/transport.h b/transport.h +index 742027f..9770777 100644 +--- a/transport.h ++++ b/transport.h +@@ -134,12 +134,23 @@ struct transport { + struct transport *transport_get(struct remote *, const char *); + + /* ++ * Check whether a transport is allowed by the environment. Type should ++ * generally be the URL scheme, as described in Documentation/git.txt ++ */ ++int is_transport_allowed(const char *type); ++ ++/* + * 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 ++ * and die otherwise. + */ + void transport_check_allowed(const char *type); + ++/* ++ * Returns true if the user has attempted to turn on protocol ++ * restrictions at all. ++ */ ++int transport_restrict_protocols(void); ++ + /* Transport options which apply to git:// and scp-style URLs */ + + /* The program to use on the remote side to send a pack */ +-- +2.1.0 + diff --git a/0004-http-limit-redirection-to-protocol-whitelist.patch b/0004-http-limit-redirection-to-protocol-whitelist.patch new file mode 100644 index 0000000..95ff91f --- /dev/null +++ b/0004-http-limit-redirection-to-protocol-whitelist.patch @@ -0,0 +1,106 @@ +From b82f2606edf3640e40ca4d4e0091fd15104c765c Mon Sep 17 00:00:00 2001 +From: Petr Stodulka +Date: Wed, 28 Oct 2015 17:27:58 +0100 +Subject: [PATCH 4/5] 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). +--- + Documentation/git.txt | 6 +----- + http.c | 17 +++++++++++++++++ + 2 files changed, 18 insertions(+), 5 deletions(-) + +diff --git a/Documentation/git.txt b/Documentation/git.txt +index 71ba92b..d65e6bf 100644 +--- a/Documentation/git.txt ++++ b/Documentation/git.txt +@@ -1095,11 +1095,7 @@ 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]] + ------------------------ +diff --git a/http.c b/http.c +index e9c6fdd..8a71f9e 100644 +--- a/http.c ++++ b/http.c +@@ -9,6 +9,7 @@ + #include "version.h" + #include "pkt-line.h" + #include "gettext.h" ++#include "transport.h" + + int active_requests; + int http_is_verbose; +@@ -340,6 +341,7 @@ 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"); +@@ -399,6 +401,21 @@ 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); +-- +2.1.0 + diff --git a/0005-http-limit-redirection-depth.patch b/0005-http-limit-redirection-depth.patch new file mode 100644 index 0000000..e900dd6 --- /dev/null +++ b/0005-http-limit-redirection-depth.patch @@ -0,0 +1,31 @@ +From 653f7dc379a20d79728e6e77a07a718d9475e4c0 Mon Sep 17 00:00:00 2001 +From: Petr Stodulka +Date: Wed, 28 Oct 2015 17:30:24 +0100 +Subject: [PATCH 5/5] http: limit redirection depth + +By default, libcurl will follow circular http redirects +forever. Let's put a cap on this so that somebody who can +trigger an automated fetch of an arbitrary repository (e.g., +for CI) cannot convince git to loop infinitely. + +The value chosen is 20, which is the same default that +Firefox uses. +--- + http.c | 1 + + 1 file changed, 1 insertion(+) + +diff --git a/http.c b/http.c +index 8a71f9e..45348fb 100644 +--- a/http.c ++++ b/http.c +@@ -396,6 +396,7 @@ static CURL *get_curl_handle(void) + } + + curl_easy_setopt(result, CURLOPT_FOLLOWLOCATION, 1); ++ curl_easy_setopt(result, CURLOPT_MAXREDIRS, 20); + #if LIBCURL_VERSION_NUM >= 0x071301 + curl_easy_setopt(result, CURLOPT_POSTREDIR, CURL_REDIR_POST_ALL); + #elif LIBCURL_VERSION_NUM >= 0x071101 +-- +2.1.0 + diff --git a/git.spec b/git.spec index 09ce465..0c72f52 100644 --- a/git.spec +++ b/git.spec @@ -44,7 +44,7 @@ Name: git Version: 2.4.3 -Release: 6%{?dist} +Release: 7%{?dist} Summary: Fast Version Control System License: GPLv2 Group: Development/Tools @@ -67,6 +67,13 @@ Patch3: git-1.7-el5-emacs-support.patch Patch4: git-infinite-loop.patch Patch5: git-2.4.3-stash-revert.patch +# set of patches for security bug (solved since 2.6.1) +Patch6: 0001-transport-add-a-protocol-whitelist-environment-varia.patch +Patch7: 0002-submodule-allow-only-certain-protocols-for-submodule.patch +Patch8: 0003-transport-refactor-protocol-whitelist-code.patch +Patch9: 0004-http-limit-redirection-to-protocol-whitelist.patch +Patch10: 0005-http-limit-redirection-depth.patch + BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n) %if ! %{use_prebuilt_docs} && ! 0%{?_without_docs} @@ -295,6 +302,11 @@ Requires: emacs-git = %{version}-%{release} %endif %patch4 -p1 %patch5 -p1 +%patch6 -p1 +%patch7 -p1 +%patch8 -p1 +%patch9 -p1 +%patch10 -p1 %if %{use_prebuilt_docs} mkdir -p prebuilt_docs/{html,man} @@ -613,14 +625,18 @@ rm -rf %{buildroot} # No files for you! %changelog -* Mon Jun 22 2015 Petr Stodulka - 2.4.3-6 +* Wed Oct 28 2015 Petr Stodulka - 2.4.3-7 +- fix arbitrary code execution via crafted URLs + Resolves: #1269797 + +* Mon Jun 22 2015 Petr Stodulka - 2.4.3-6 - fix #1242034 - "git stash save -k" followed by "git stash apply" fails used upstream solution from git-2.4.6 (revert relevant commit) -* Mon Jun 22 2015 Petr Stodulka - 2.4.3-5 +* Mon Jun 22 2015 Petr Stodulka - 2.4.3-5 - apply git-infinite-loop.patch -* Mon Jun 22 2015 Petr Stodulka - 2.4.3-4 +* Mon Jun 22 2015 Petr Stodulka - 2.4.3-4 - git-svn - added requires for perl-Digest-MD5 (#1218176) - solve troubles with infinite loop due to broken symlink (probably shouldn't be problem here, but it's reproducible manually)