neocgit

a more 'modern' version of cgit
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commit fe36f84d843cd755c6dab629a0758264de5bcc00
parent 2a1ead3efb940b7359bcc706c19bd8ddb0de7a11
Author: Jason A. Donenfeld <Jason@zx2c4.com>
Date:   Sat, 25 May 2013 19:47:15 +0200

ui-summary: Disallow directory traversal

Using the url= query string, it was possible request arbitrary files
from the filesystem if the readme for a given page was set to a
filesystem file. The following request would return my /etc/passwd file:

http://git.zx2c4.com/?url=/somerepo/about/../../../../etc/passwd
http://data.zx2c4.com/cgit-directory-traversal.png

This fix uses realpath(3) to canonicalize all paths, and then compares
the base components.

This fix introduces a subtle timing attack, whereby a client can check
whether or not strstr is called using timing measurements in order
to determine if a given file exists on the filesystem.

This fix also does not account for filesystem race conditions (TOCTOU)
in resolving symlinks.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Diffstat:
Mui-summary.c | 16++++++++++++++++
1 file changed, 16 insertions(+), 0 deletions(-)

diff --git a/ui-summary.c b/ui-summary.c @@ -99,6 +99,7 @@ void cgit_print_summary() void cgit_parse_readme(const char *readme, const char *path, char **filename, char **ref, struct cgit_repo *repo) { const char *slash, *colon; + char *resolved_base, *resolved_full; *filename = NULL; *ref = NULL; @@ -133,7 +134,19 @@ void cgit_parse_readme(const char *readme, const char *path, char **filename, ch } *filename = xmalloc(slash - readme + 1 + strlen(path) + 1); strncpy(*filename, readme, slash - readme + 1); + if (!(*ref)) + resolved_base = realpath(*filename, NULL); strcpy(*filename + (slash - readme + 1), path); + if (!(*ref)) + resolved_full = realpath(*filename, NULL); + if (!(*ref) && (!resolved_base || !resolved_full || strstr(resolved_full, resolved_base) != resolved_full)) { + free(*filename); + *filename = NULL; + } + if (!(*ref)) { + free(resolved_base); + free(resolved_full); + } } else *filename = xstrdup(readme); } @@ -143,6 +156,9 @@ void cgit_print_repo_readme(char *path) char *filename, *ref; cgit_parse_readme(ctx.repo->readme, path, &filename, &ref, ctx.repo); + if (!filename) + return; + /* Print the calculated readme, either from the git repo or from the * filesystem, while applying the about-filter. */