git-for-windows/git
1
0
Fork 0
mirror of https://github.com/git-for-windows/git.git synced 2026-06-13 08:57:56 -05:00
Code Issues Packages Projects Releases 335 Wiki Activity

promisor-remote: trust known remotes matching acceptFromServerUrl

Browse Source 
A previous commit introduced the `promisor.acceptFromServerUrl` config
variable along with the machinery to parse and validate the URL glob
patterns and optional remote name prefixes it contains. However, these
URL patterns are not yet tied into the client's acceptance logic.

When a promisor remote is already configured locally, its fields (like
authentication tokens) may occasionally need to be refreshed by the
server. If `promisor.acceptFromServer` is set to the secure default
("None"), these updates are rejected, potentially causing future
fetches to fail.

To enable such targeted updates for trusted URLs, let's use the URL
patterns from `promisor.acceptFromServerUrl` as an additional URL
based allowlist.

Concretely, let's check the advertised URLs against the URL glob
patterns by introducing a new small helper function called
url_matches_accept_list(), which iterates over the glob patterns and
returns the first matching allowed_url entry (or NULL).

The URL matching is done component by component: scheme and port are
compared exactly, the host and path are matched with wildmatch().
Before matching, the advertised URL is passed through url_normalize()
so that case variations in the scheme/host, percent-encoding tricks,
and ".." path segments cannot bypass the allowlist.

The username and password components of the URL are intentionally
ignored during matching to allow servers to rotate them, though using
the 'token' field of the capability is preferred over embedding
credentials in the URL.

Let's then use this helper in should_accept_remote() so that a known
remote whose URL matches the allowlist is accepted.

To prepare for this new logic, let's also:

 - Add an 'accept_urls' parameter to should_accept_remote().

 - Replace the BUG() guard in the ACCEPT_KNOWN_URL case with an
   explicit 'if (accept == ACCEPT_KNOWN_URL) return' and a new
   BUG() guard in the ACCEPT_NONE case.

 - Call accept_from_server_url() from filter_promisor_remote()
   and relax its early return so that the function is entered when
   `accept_urls` has entries even if `accept == ACCEPT_NONE`.

With this, many organizations may only need something like:

  git config set --global \
          promisor.acceptFromServerUrl "https://my-org.com/*"

to accept only their own remotes. And if they need to accept additional
remotes in some specific repos, they can also set:

  git config set promisor.acceptFromServer knownUrl

and configure the additional remote manually only in the repos where
they are needed.

Let's then properly document `promisor.acceptFromServerUrl` in
"promisor.adoc" as an additive security allowlist for known remotes,
including the URL normalization behavior and the component-wise
matching, and let's mention it in "gitprotocol-v2.adoc".

Also let's clarify in the documentation how
`promisor.acceptFromServerUrl` interacts with
`promisor.acceptFromServer`:

 - Precedence: when both options are set,
   `promisor.acceptFromServerUrl` is consulted first. If a matching
   pattern leads to acceptance, the remote is accepted regardless of
   `promisor.acceptFromServer`. Otherwise the decision is left to
   `promisor.acceptFromServer`.

 - URL-mismatch guard: even when the advertised URL matches the
   allowlist, an already-existing client-side remote whose configured
   URL differs from the advertised one is not accepted through
   `promisor.acceptFromServerUrl`. `promisor.acceptFromServer=all` and
   `=knownName` keep their pre-existing, looser semantics.

The precedence paragraph is intentionally scoped here to known remotes
only (field updates). A following commit that introduces auto-creation
of unknown remotes will extend it to cover that case as well.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Christian Couder
2026-05-27 16:08:18 +02:00
committed by Junio C Hamano
parent 78e0d9b0e4
commit 5dd8043581
4 changed files with 244 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

76
Documentation/config/promisor.adoc
View File

@@ -51,6 +51,82 @@ promisor.acceptFromServer::
to "fetch" and "clone" requests from the client. Name and URL
comparisons are case sensitive. See linkgit:gitprotocol-v2[5].
promisor.acceptFromServerUrl::
A glob pattern to specify which server-advertised URLs a
client is allowed to act on. When a URL matches, the client
will accept the advertised remote as a promisor remote and may
automatically accept field updates (such as authentication
tokens) from the server, even if `promisor.acceptFromServer`
is set to `none` (the default).
+
This option can appear multiple times in config files. An advertised
URL will be accepted if it matches _ANY_ glob pattern specified by
this option in _ANY_ config file read by Git.
+
When both `promisor.acceptFromServer` and `promisor.acceptFromServerUrl`
are set, `promisor.acceptFromServerUrl` is consulted first and takes
precedence: if a matching pattern leads to acceptance (by accepting
field updates for a known remote whose URL matches both the local
configuration and the allowlist), the advertised remote is accepted
regardless of the `promisor.acceptFromServer` setting. If no pattern
in `promisor.acceptFromServerUrl` triggers acceptance, the decision
is left to `promisor.acceptFromServer`.
+
Note however that, even when an advertised URL matches a pattern in
`promisor.acceptFromServerUrl`, an already-existing remote on the
client whose name matches the advertised name but whose configured URL
differs from the advertised one will _NOT_ be accepted through
`promisor.acceptFromServerUrl`. This prevents a server from silently
re-pointing an existing client-side remote at a different URL. (Such a
remote may still be accepted through `promisor.acceptFromServer=all`
or `=knownName`, which have their own, looser semantics; see the
documentation of that option.)
+
Be _VERY_ careful with these patterns: `*` matches any sequence of
characters within the 'host' and 'path' parts of a URL (but cannot
cross part boundaries). An overly broad pattern is a major security
risk, as a matching URL allows a server to update fields (such as
authentication tokens) on known remotes without further confirmation.
To minimize security risks, follow these guidelines:
+
--
1. Start with a secure protocol scheme, like `https://` or `ssh://`.
+
2. Only allow domain names or paths where you control and trust _ALL_
the content. Be especially careful with shared hosting platforms
like `github.com` or `gitlab.com`. A broad pattern like
`https://gitlab.com/*` is dangerous because it trusts every
repository on the entire platform. Always restrict such patterns to
your specific organization or namespace (e.g.,
`https://gitlab.com/your-org/*`).
+
3. Never use globs at the end of domain names. For example,
`https://cdn.your-org.com/*` might be safe, but
`https://cdn.your-org.com*/*` is a major security risk because
the latter matches `https://cdn.your-org.com.hacker.net/repo`.
+
4. Be careful using globs at the beginning of domain names. While the
code ensures a `*` in the host cannot cross into the path, a
pattern like `https://*.example.com/*` will still match any
subdomain. This is extremely dangerous on shared hosting platforms
(e.g., `https://*.github.io/*` trusts every user's site on the
entire platform).
--
+
Before matching, both the advertised URL and the pattern are
normalized: the scheme and host are lowercased, percent-encoded
characters are decoded where possible, and path segments like `..`
are resolved. The port must also match exactly (e.g.,
`https://example.com:8080/*` will not match a URL advertised on
port 9999). The username and password components of the URL are
ignored during matching. Note that embedding credentials in URLs is
discouraged. Passing authentication tokens via the `token` field of
the `promisor-remote` capability is strongly preferred.
+
For the security implications of accepting a promisor remote, see the
documentation of `promisor.acceptFromServer`. For details on the
protocol, see linkgit:gitprotocol-v2[5].
promisor.checkFields::
A comma or space separated list of additional remote related
field names. A client checks if the values of these fields

9
Documentation/gitprotocol-v2.adoc
View File

@@ -866,10 +866,11 @@ the server advertised, the client shouldn't advertise the
On the server side, the "promisor.advertise" and "promisor.sendFields"
configuration options can be used to control what it advertises. On
the client side, the "promisor.acceptFromServer" configuration option
can be used to control what it accepts, and the "promisor.storeFields"
option, to control what it stores. See the documentation of these
configuration options in linkgit:git-config[1] for more information.
the client side, the "promisor.acceptFromServer" and
"promisor.acceptFromServerUrl" configuration options can be used to
control what it accepts, and the "promisor.storeFields" option, to
control what it stores. See the documentation of these configuration
options in linkgit:git-config[1] for more information.
Note that in the future it would be nice if the "promisor-remote"
protocol capability could be used by the server, when responding to

102
promisor-remote.c
View File

@@ -14,6 +14,7 @@
#include "url.h"
#include "urlmatch.h"
#include "version.h"
#include "wildmatch.h"
struct promisor_remote_config {
struct promisor_remote *promisors;
@@ -742,8 +743,79 @@ static void load_accept_from_server_url(struct repository *repo,
}
}
static bool match_pattern_url(const char *pat, size_t pat_len,
const char *url, size_t url_len)
{
char *p_str = xstrndup(pat, pat_len);
char *u_str = xstrndup(url, url_len);
bool res = !wildmatch(p_str, u_str, 0);
free(p_str);
free(u_str);
return res;
}
static bool match_one_url(const struct url_info *pi, const struct url_info *ui)
{
const char *pat = pi->url;
const char *url = ui->url;
/*
* Schemes must match exactly. They are case-folded by
* url_normalize(), so strncmp() suffices.
*/
if (pi->scheme_len != ui->scheme_len || strncmp(pat, url, pi->scheme_len))
return false;
/*
* Ports must match exactly. url_normalize() strips default
* ports (like 443 for https), so length and content
* comparisons are sufficient.
*/
if (pi->port_len != ui->port_len ||
strncmp(pat + pi->port_off, url + ui->port_off, pi->port_len))
return false;
/*
* Match host and path separately to prevent a '*' in the host
* portion of the pattern from matching across the '/'
* boundary into the path.
*/
return match_pattern_url(pat + pi->host_off, pi->host_len,
url + ui->host_off, ui->host_len) &&
match_pattern_url(pat + pi->path_off, pi->path_len,
url + ui->path_off, ui->path_len);
}
static struct allowed_url *url_matches_accept_list(
struct string_list *accept_urls, const char *url)
{
struct string_list_item *item;
struct url_info url_info;
url_info.url = url_normalize(url, &url_info);
if (!url_info.url)
return NULL;
for_each_string_list_item(item, accept_urls) {
struct allowed_url *allowed = item->util;
if (match_one_url(&allowed->pattern_info, &url_info)) {
free(url_info.url);
return allowed;
}
}
free(url_info.url);
return NULL;
}
static int should_accept_remote(enum accept_promisor accept,
struct promisor_info *advertised,
struct string_list *accept_urls,
struct string_list *config_info)
{
struct promisor_info *p;
@@ -756,23 +828,27 @@ static int should_accept_remote(enum accept_promisor accept,
"this remote should have been rejected earlier",
remote_name);
if (accept == ACCEPT_ALL)
return all_fields_match(advertised, config_info, NULL);
/* Get config info for that promisor remote */
item = string_list_lookup(config_info, remote_name);
if (!item)
if (!item) {
/* We don't know about that remote */
if (accept == ACCEPT_ALL)
return all_fields_match(advertised, config_info, NULL);
return 0;
}
p = item->util;
if (accept == ACCEPT_KNOWN_NAME)
/* Known remote in the allowlist? */
if (!strcmp(p->url, remote_url) && url_matches_accept_list(accept_urls, remote_url))
return all_fields_match(advertised, config_info, p);
if (accept != ACCEPT_KNOWN_URL)
BUG("Unhandled 'enum accept_promisor' value '%d'", accept);
if (accept == ACCEPT_ALL)
return all_fields_match(advertised, config_info, NULL);
if (accept == ACCEPT_KNOWN_NAME)
return all_fields_match(advertised, config_info, p);
if (strcmp(p->url, remote_url)) {
warning(_("known remote named '%s' but with URL '%s' instead of '%s', "
@@ -781,7 +857,13 @@ static int should_accept_remote(enum accept_promisor accept,
return 0;
}
return all_fields_match(advertised, config_info, p);
if (accept == ACCEPT_KNOWN_URL)
return all_fields_match(advertised, config_info, p);
if (accept != ACCEPT_NONE)
BUG("Unhandled 'enum accept_promisor' value '%d'", accept);
return 0;
}
static int skip_field_name_prefix(const char *elem, const char *field_name, const char **value)
@@ -991,7 +1073,7 @@ static void filter_promisor_remote(struct repository *repo,
/* Load and validate the acceptFromServerUrl config */
load_accept_from_server_url(repo, &accept_urls);
if (accept == ACCEPT_NONE)
if (accept == ACCEPT_NONE && !accept_urls.nr)
return;
/* Parse remote info received */
@@ -1011,7 +1093,7 @@ static void filter_promisor_remote(struct repository *repo,
string_list_sort(&config_info);
}
if (should_accept_remote(accept, advertised, &config_info)) {
if (should_accept_remote(accept, advertised, &accept_urls, &config_info)) {
if (!store_info)
store_info = store_info_new(repo);
if (promisor_store_advertised_fields(advertised, store_info))

71
t/t5710-promisor-remote-capability.sh
View File

@@ -387,6 +387,77 @@ test_expect_success "clone with 'KnownUrl' and empty url, so not advertised" '
check_missing_objects server 1 "$oid"
'
test_expect_success "clone with 'None' but URL allowlisted" '
git -C server config promisor.advertise true &&
test_when_finished "rm -rf client" &&
GIT_NO_LAZY_FETCH=0 git clone -c remote.lop.promisor=true \
-c remote.lop.fetch="+refs/heads/*:refs/remotes/lop/*" \
-c remote.lop.url="$TRASH_DIRECTORY_URL/lop" \
-c promisor.acceptfromserver=None \
-c promisor.acceptFromServerUrl="$ENCODED_TRASH_DIRECTORY_URL/*" \
--no-local --filter="blob:limit=5k" server client &&
# Check that the largest object is still missing on the server
check_missing_objects server 1 "$oid"
'
test_expect_success "clone with 'None' but URL not in allowlist" '
git -C server config promisor.advertise true &&
test_when_finished "rm -rf client" &&
GIT_NO_LAZY_FETCH=0 git clone -c remote.lop.promisor=true \
-c remote.lop.fetch="+refs/heads/*:refs/remotes/lop/*" \
-c remote.lop.url="$TRASH_DIRECTORY_URL/lop" \
-c promisor.acceptfromserver=None \
-c promisor.acceptFromServerUrl="https://example.com/*" \
--no-local --filter="blob:limit=5k" server client &&
# Check that the largest object is not missing on the server
check_missing_objects server 0 "" &&
# Reinitialize server so that the largest object is missing again
initialize_server 1 "$oid"
'
test_expect_success "clone with 'None' but URL allowlisted in one pattern out of two" '
git -C server config promisor.advertise true &&
test_when_finished "rm -rf client" &&
GIT_NO_LAZY_FETCH=0 git clone -c remote.lop.promisor=true \
-c remote.lop.fetch="+refs/heads/*:refs/remotes/lop/*" \
-c remote.lop.url="$TRASH_DIRECTORY_URL/lop" \
-c promisor.acceptfromserver=None \
-c promisor.acceptFromServerUrl="https://example.com/*" \
-c promisor.acceptFromServerUrl="$ENCODED_TRASH_DIRECTORY_URL/*" \
--no-local --filter="blob:limit=5k" server client &&
# Check that the largest object is still missing on the server
check_missing_objects server 1 "$oid"
'
test_expect_success "clone with 'None', URL allowlisted, but client has different URL" '
git -C server config promisor.advertise true &&
test_when_finished "rm -rf client" &&
# The client configures "lop" with a different URL (serverTwo) than
# what the server advertises (lop). Even though the advertised URL
# matches the allowlist, the remote is rejected because the
# configured URL does not match the advertised one.
GIT_NO_LAZY_FETCH=0 git clone -c remote.lop.promisor=true \
-c remote.lop.fetch="+refs/heads/*:refs/remotes/lop/*" \
-c remote.lop.url="$TRASH_DIRECTORY_URL/serverTwo" \
-c promisor.acceptfromserver=None \
-c promisor.acceptFromServerUrl="$ENCODED_TRASH_DIRECTORY_URL/*" \
--no-local --filter="blob:limit=5k" server client &&
# Check that the largest object is not missing on the server
check_missing_objects server 0 "" &&
# Reinitialize server so that the largest object is missing again
initialize_server 1 "$oid"
'
test_expect_success "clone with invalid promisor.acceptFromServerUrl" '
git -C server config promisor.advertise true &&
test_when_finished "rm -rf client" &&