Revision 7b70e9efb18c2cc3f219af399bd384c5801ba1d7 authored by Jeff King on 16 April 2024, 08:35:33 UTC, committed by Johannes Schindelin on 17 April 2024, 20:29:56 UTC
The upload-pack command tries to avoid trusting the repository in which it's run (e.g., by not running any hooks and not using any config that contains arbitrary commands). But if the server side of a fetch or a clone is a partial clone, then either upload-pack or its child pack-objects may run a lazy "git fetch" under the hood. And it is very easy to convince fetch to run arbitrary commands. The "server" side can be a local repository owned by someone else, who would be able to configure commands that are run during a clone with the current user's permissions. This issue has been designated CVE-2024-32004. The fix in this commit's parent helps in this scenario, as well as in related scenarios using SSH to clone, where the untrusted .git directory is owned by a different user id. But if you received one as a zip file, on a USB stick, etc, it may be owned by your user but still untrusted. This has been designated CVE-2024-32465. To mitigate the issue more completely, let's disable lazy fetching entirely during `upload-pack`. While fetching from a partial repository should be relatively rare, it is certainly not an unreasonable workflow. And thus we need to provide an escape hatch. This commit works by respecting a GIT_NO_LAZY_FETCH environment variable (to skip the lazy-fetch), and setting it in upload-pack, but only when the user has not already done so (which gives us the escape hatch). The name of the variable is specifically chosen to match what has already been added in 'master' via e6d5479e7a (git: extend --no-lazy-fetch to work across subprocesses, 2024-02-27). Since we're building this fix as a backport for older versions, we could cherry-pick that patch and its earlier steps. However, we don't really need the niceties (like a "--no-lazy-fetch" option) that it offers. By using the same name, everything should just work when the two are eventually merged, but here are a few notes: - the blocking of the fetch in e6d5479e7a is incomplete! It sets fetch_if_missing to 0 when we setup the repository variable, but that isn't enough. pack-objects in particular will call prefetch_to_pack() even if that variable is 0. This patch by contrast checks the environment variable at the lowest level before we call the lazy fetch, where we can be sure to catch all code paths. Possibly the setting of fetch_if_missing from e6d5479e7a can be reverted, but it may be useful to have. For example, some code may want to use that flag to change behavior before it gets to the point of trying to start the fetch. At any rate, that's all outside the scope of this patch. - there's documentation for GIT_NO_LAZY_FETCH in e6d5479e7a. We can live without that here, because for the most part the user shouldn't need to set it themselves. The exception is if they do want to override upload-pack's default, and that requires a separate documentation section (which is added here) - it would be nice to use the NO_LAZY_FETCH_ENVIRONMENT macro added by e6d5479e7a, but those definitions have moved from cache.h to environment.h between 2.39.3 and master. I just used the raw string literals, and we can replace them with the macro once this topic is merged to master. At least with respect to CVE-2024-32004, this does render this commit's parent commit somewhat redundant. However, it is worth retaining that commit as defense in depth, and because it may help other issues (e.g., symlink/hardlink TOCTOU races, where zip files are not really an interesting attack vector). The tests in t0411 still pass, but now we have _two_ mechanisms ensuring that the evil command is not run. Let's beef up the existing ones to check that they failed for the expected reason, that we refused to run upload-pack at all with an alternate user id. And add two new ones for the same-user case that both the restriction and its escape hatch. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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path.h
#ifndef PATH_H
#define PATH_H
struct repository;
struct strbuf;
/*
* The result to all functions which return statically allocated memory may be
* overwritten by another call to _any_ one of these functions. Consider using
* the safer variants which operate on strbufs or return allocated memory.
*/
/*
* Return a statically allocated path.
*/
const char *mkpath(const char *fmt, ...)
__attribute__((format (printf, 1, 2)));
/*
* Return a path.
*/
char *mkpathdup(const char *fmt, ...)
__attribute__((format (printf, 1, 2)));
/*
* Construct a path and place the result in the provided buffer `buf`.
*/
char *mksnpath(char *buf, size_t n, const char *fmt, ...)
__attribute__((format (printf, 3, 4)));
/*
* The `git_common_path` family of functions will construct a path into a
* repository's common git directory, which is shared by all worktrees.
*/
/*
* Constructs a path into the common git directory of repository `repo` and
* append it in the provided buffer `sb`.
*/
void strbuf_git_common_path(struct strbuf *sb,
const struct repository *repo,
const char *fmt, ...)
__attribute__((format (printf, 3, 4)));
/*
* Return a statically allocated path into the main repository's
* (the_repository) common git directory.
*/
const char *git_common_path(const char *fmt, ...)
__attribute__((format (printf, 1, 2)));
/*
* The `git_path` family of functions will construct a path into a repository's
* git directory.
*
* These functions will perform adjustments to the resultant path to account
* for special paths which are either considered common among worktrees (e.g.
* paths into the object directory) or have been explicitly set via an
* environment variable or config (e.g. path to the index file).
*
* For an exhaustive list of the adjustments made look at `common_list` and
* `adjust_git_path` in path.c.
*/
/*
* Return a path into the git directory of repository `repo`.
*/
char *repo_git_path(const struct repository *repo,
const char *fmt, ...)
__attribute__((format (printf, 2, 3)));
/*
* Construct a path into the git directory of repository `repo` and append it
* to the provided buffer `sb`.
*/
void strbuf_repo_git_path(struct strbuf *sb,
const struct repository *repo,
const char *fmt, ...)
__attribute__((format (printf, 3, 4)));
/*
* Return a statically allocated path into the main repository's
* (the_repository) git directory.
*/
const char *git_path(const char *fmt, ...)
__attribute__((format (printf, 1, 2)));
/*
* Return a path into the main repository's (the_repository) git directory.
*/
char *git_pathdup(const char *fmt, ...)
__attribute__((format (printf, 1, 2)));
/*
* Construct a path into the main repository's (the_repository) git directory
* and place it in the provided buffer `buf`, the contents of the buffer will
* be overridden.
*/
char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
__attribute__((format (printf, 2, 3)));
/*
* Construct a path into the main repository's (the_repository) git directory
* and append it to the provided buffer `sb`.
*/
void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
__attribute__((format (printf, 2, 3)));
/*
* Return a path into the worktree of repository `repo`.
*
* If the repository doesn't have a worktree NULL is returned.
*/
char *repo_worktree_path(const struct repository *repo,
const char *fmt, ...)
__attribute__((format (printf, 2, 3)));
/*
* Construct a path into the worktree of repository `repo` and append it
* to the provided buffer `sb`.
*
* If the repository doesn't have a worktree nothing will be appended to `sb`.
*/
void strbuf_repo_worktree_path(struct strbuf *sb,
const struct repository *repo,
const char *fmt, ...)
__attribute__((format (printf, 3, 4)));
/*
* Return a path into a submodule's git directory located at `path`. `path`
* must only reference a submodule of the main repository (the_repository).
*/
char *git_pathdup_submodule(const char *path, const char *fmt, ...)
__attribute__((format (printf, 2, 3)));
/*
* Construct a path into a submodule's git directory located at `path` and
* append it to the provided buffer `sb`. `path` must only reference a
* submodule of the main repository (the_repository).
*/
int strbuf_git_path_submodule(struct strbuf *sb, const char *path,
const char *fmt, ...)
__attribute__((format (printf, 3, 4)));
void report_linked_checkout_garbage(void);
/*
* You can define a static memoized git path like:
*
* static GIT_PATH_FUNC(git_path_foo, "FOO")
*
* or use one of the global ones below.
*/
#define GIT_PATH_FUNC(func, filename) \
const char *func(void) \
{ \
static char *ret; \
if (!ret) \
ret = git_pathdup(filename); \
return ret; \
}
#define REPO_GIT_PATH_FUNC(var, filename) \
const char *git_path_##var(struct repository *r) \
{ \
if (!r->cached_paths.var) \
r->cached_paths.var = repo_git_path(r, filename); \
return r->cached_paths.var; \
}
const char *git_path_squash_msg(struct repository *r);
const char *git_path_merge_msg(struct repository *r);
const char *git_path_merge_rr(struct repository *r);
const char *git_path_merge_mode(struct repository *r);
const char *git_path_merge_head(struct repository *r);
const char *git_path_merge_autostash(struct repository *r);
const char *git_path_auto_merge(struct repository *r);
const char *git_path_fetch_head(struct repository *r);
const char *git_path_shallow(struct repository *r);
int ends_with_path_components(const char *path, const char *components);
#endif /* PATH_H */
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