cgitsb/ui-summary.c
Jason A. Donenfeld fe36f84d84 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>
2013-05-25 20:33:28 +02:00

182 lines
4.4 KiB
C

/* ui-summary.c: functions for generating repo summary page
*
* Copyright (C) 2006 Lars Hjemli
* Copyright (C) 2010 Jason A. Donenfeld <Jason@zx2c4.com>
*
* Licensed under GNU General Public License v2
* (see COPYING for full license text)
*/
#include "cgit.h"
#include "ui-summary.h"
#include "html.h"
#include "ui-log.h"
#include "ui-refs.h"
#include "ui-blob.h"
static void print_url(char *base, char *suffix)
{
int columns = 3;
struct strbuf basebuf = STRBUF_INIT;
if (ctx.repo->enable_log_filecount)
columns++;
if (ctx.repo->enable_log_linecount)
columns++;
if (!base || !*base)
return;
if (suffix && *suffix) {
strbuf_addf(&basebuf, "%s/%s", base, suffix);
base = basebuf.buf;
}
htmlf("<tr><td colspan='%d'><a href='", columns);
html_url_path(base);
html("'>");
html_txt(base);
html("</a></td></tr>\n");
strbuf_release(&basebuf);
}
static void print_urls(char *txt, char *suffix)
{
char *h = txt, *t, c;
int urls = 0;
int columns = 3;
if (ctx.repo->enable_log_filecount)
columns++;
if (ctx.repo->enable_log_linecount)
columns++;
while (h && *h) {
while (h && *h == ' ')
h++;
if (!*h)
break;
t = h;
while (t && *t && *t != ' ')
t++;
c = *t;
*t = 0;
if (urls++ == 0) {
htmlf("<tr class='nohover'><td colspan='%d'>&nbsp;</td></tr>", columns);
htmlf("<tr><th class='left' colspan='%d'>Clone</th></tr>\n", columns);
}
print_url(h, suffix);
*t = c;
h = t;
}
}
void cgit_print_summary()
{
int columns = 3;
if (ctx.repo->enable_log_filecount)
columns++;
if (ctx.repo->enable_log_linecount)
columns++;
html("<table summary='repository info' class='list nowrap'>");
cgit_print_branches(ctx.cfg.summary_branches);
htmlf("<tr class='nohover'><td colspan='%d'>&nbsp;</td></tr>", columns);
cgit_print_tags(ctx.cfg.summary_tags);
if (ctx.cfg.summary_log > 0) {
htmlf("<tr class='nohover'><td colspan='%d'>&nbsp;</td></tr>", columns);
cgit_print_log(ctx.qry.head, 0, ctx.cfg.summary_log, NULL,
NULL, NULL, 0, 0, 0);
}
if (ctx.repo->clone_url)
print_urls(expand_macros(ctx.repo->clone_url), NULL);
else if (ctx.cfg.clone_prefix)
print_urls(ctx.cfg.clone_prefix, ctx.repo->url);
html("</table>");
}
/* The caller must free filename and ref after calling this. */
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;
if (!readme || !(*readme))
return;
/* Check if the readme is tracked in the git repo. */
colon = strchr(readme, ':');
if (colon && strlen(colon) > 1) {
/* If it starts with a colon, we want to use
* the default branch */
if (colon == readme && repo->defbranch)
*ref = xstrdup(repo->defbranch);
else
*ref = xstrndup(readme, colon - readme);
readme = colon + 1;
}
/* Prepend repo path to relative readme path unless tracked. */
if (!(*ref) && *readme != '/')
readme = fmtalloc("%s/%s", repo->path, readme);
/* If a subpath is specified for the about page, make it relative
* to the directory containing the configured readme. */
if (path) {
slash = strrchr(readme, '/');
if (!slash) {
if (!colon)
return;
slash = colon;
}
*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);
}
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.
*/
html("<div id='summary'>");
if (ctx.repo->about_filter) {
ctx.repo->about_filter->argv[1] = filename;
cgit_open_filter(ctx.repo->about_filter);
}
if (ref)
cgit_print_file(filename, ref);
else
html_include(filename);
if (ctx.repo->about_filter) {
cgit_close_filter(ctx.repo->about_filter);
ctx.repo->about_filter->argv[1] = NULL;
}
html("</div>");
free(filename);
free(ref);
}