git/builtin/symbolic-ref.c
Linus Torvalds 04ede97211 symbolic-ref: refuse to set syntactically invalid target
You can feed absolute garbage to symbolic-ref as a target like:

  git symbolic-ref HEAD refs/heads/foo..bar

While this doesn't technically break the repo entirely (our "is it a git
directory" detector looks only for "refs/" at the start), we would never
resolve such a ref, as the ".." is invalid within a refname.

Let's flag these as invalid at creation time to help the caller realize
that what they're asking for is bogus.

A few notes:

  - We use REFNAME_ALLOW_ONELEVEL here, which lets:

     git update-ref refs/heads/foo FETCH_HEAD

    continue to work. It's unclear whether anybody wants to do something
    so odd, but it does work now, so this is erring on the conservative
    side. There's a test to make sure we didn't accidentally break this,
    but don't take that test as an endorsement that it's a good idea, or
    something we might not change in the future.

  - The test in t4202-log.sh checks how we handle such an invalid ref on
    the reading side, so it has to be updated to touch the HEAD file
    directly.

  - We need to keep our HEAD-specific check for "does it start with
    refs/". The ALLOW_ONELEVEL flag means we won't be enforcing that for
    other refs, but HEAD is special here because of the checks in
    validate_headref().

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-08-01 12:17:13 -07:00

82 lines
2.2 KiB
C

#include "builtin.h"
#include "config.h"
#include "cache.h"
#include "refs.h"
#include "parse-options.h"
static const char * const git_symbolic_ref_usage[] = {
N_("git symbolic-ref [<options>] <name> [<ref>]"),
N_("git symbolic-ref -d [-q] <name>"),
NULL
};
static int check_symref(const char *HEAD, int quiet, int shorten, int print)
{
int flag;
const char *refname = resolve_ref_unsafe(HEAD, 0, NULL, &flag);
if (!refname)
die("No such ref: %s", HEAD);
else if (!(flag & REF_ISSYMREF)) {
if (!quiet)
die("ref %s is not a symbolic ref", HEAD);
else
return 1;
}
if (print) {
char *to_free = NULL;
if (shorten)
refname = to_free = shorten_unambiguous_ref(refname, 0);
puts(refname);
free(to_free);
}
return 0;
}
int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
{
int quiet = 0, delete = 0, shorten = 0, ret = 0;
const char *msg = NULL;
struct option options[] = {
OPT__QUIET(&quiet,
N_("suppress error message for non-symbolic (detached) refs")),
OPT_BOOL('d', "delete", &delete, N_("delete symbolic ref")),
OPT_BOOL(0, "short", &shorten, N_("shorten ref output")),
OPT_STRING('m', NULL, &msg, N_("reason"), N_("reason of the update")),
OPT_END(),
};
git_config(git_default_config, NULL);
argc = parse_options(argc, argv, prefix, options,
git_symbolic_ref_usage, 0);
if (msg && !*msg)
die("Refusing to perform update with empty message");
if (delete) {
if (argc != 1)
usage_with_options(git_symbolic_ref_usage, options);
ret = check_symref(argv[0], 1, 0, 0);
if (ret)
die("Cannot delete %s, not a symbolic ref", argv[0]);
if (!strcmp(argv[0], "HEAD"))
die("deleting '%s' is not allowed", argv[0]);
return delete_ref(NULL, argv[0], NULL, REF_NO_DEREF);
}
switch (argc) {
case 1:
ret = check_symref(argv[0], quiet, shorten, 1);
break;
case 2:
if (!strcmp(argv[0], "HEAD") &&
!starts_with(argv[1], "refs/"))
die("Refusing to point HEAD outside of refs/");
if (check_refname_format(argv[1], REFNAME_ALLOW_ONELEVEL) < 0)
die("Refusing to set '%s' to invalid ref '%s'", argv[0], argv[1]);
ret = !!create_symref(argv[0], argv[1], msg);
break;
default:
usage_with_options(git_symbolic_ref_usage, options);
}
return ret;
}