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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>
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parent
2a1ead3efb
commit
fe36f84d84
16
ui-summary.c
16
ui-summary.c
@ -99,6 +99,7 @@ void cgit_print_summary()
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void cgit_parse_readme(const char *readme, const char *path, char **filename, char **ref, struct cgit_repo *repo)
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{
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const char *slash, *colon;
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char *resolved_base, *resolved_full;
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*filename = NULL;
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*ref = NULL;
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@ -133,7 +134,19 @@ void cgit_parse_readme(const char *readme, const char *path, char **filename, ch
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}
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*filename = xmalloc(slash - readme + 1 + strlen(path) + 1);
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strncpy(*filename, readme, slash - readme + 1);
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if (!(*ref))
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resolved_base = realpath(*filename, NULL);
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strcpy(*filename + (slash - readme + 1), path);
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if (!(*ref))
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resolved_full = realpath(*filename, NULL);
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if (!(*ref) && (!resolved_base || !resolved_full || strstr(resolved_full, resolved_base) != resolved_full)) {
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free(*filename);
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*filename = NULL;
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}
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if (!(*ref)) {
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free(resolved_base);
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free(resolved_full);
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}
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} else
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*filename = xstrdup(readme);
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}
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@ -143,6 +156,9 @@ void cgit_print_repo_readme(char *path)
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char *filename, *ref;
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cgit_parse_readme(ctx.repo->readme, path, &filename, &ref, ctx.repo);
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if (!filename)
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return;
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/* Print the calculated readme, either from the git repo or from the
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* filesystem, while applying the about-filter.
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*/
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