[PATCH] fixup! config: allow inaccessible configuration under $HOME
- From
Jonathan Nieder <jrnieder@gmail.com>
- Date
- Apr 12, 2013, 20:34 UTC
- Message-ID
- <20130412203442.GT27070@google.com>
- In-Reply-To
- <20130412193755.GA5329@sigill.intra.peff.net>
A cleanup from Jeff King.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> --- wrapper.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
Jeff King wrote:
Show 10 quoted lines
> I kind of wonder if we are doing anything with the check at this point. > I suppose ENOMEM and EIO are the only interesting things left at this > point. The resulting code would be much nicer if the patch were just: > > -access_or_die(...); > +access(...); > > but I guess those conditions are still worth checking for, especially if > we think an attacker could trigger ENOMEM intentionally. To be honest, I > am not sure how possible that is, but it is not that hard to do so.
Yeah, I was tempted to go the plain access() route. The case that convinced me not to is that I wouldn't want to think about whether there could have been a blip in $HOME producing EIO when wondering how some malformed object had been accepted. The ENOMEM case just seemed simpler to explain.
I would also be surprised if it is easy to control kernel ENOMEM carefully enough to exploit (a more likely DoS outcome is crashing programs or a kernel assertion failure, which are more harmless in their way). I've given up on predicting what is too hard or easy enough for security folks. I couldn't think of an obviously easier vulnerability that is already accepted to put my mind at ease.
[...]
> I know you are trying to be flexible with the flag,
I was mostly worried about damage to readability if we end up needing to go further down this direction. The opportunity to look at all call sites was also nice.
[...]
Show 5 quoted lines
> static int access_error_is_ok(int err, int flag)
> {
> return err == ENOENT || errno == ENOTDIR ||
> (flag & ACCESS_EACCES_OK && err == EACCES);
> }Nice. Here's a patch for squashing in.
diff --git a/wrapper.c b/wrapper.c index e860ad1..29a866b 100644 --- a/wrapper.c +++ b/wrapper.c @@ -408,11 +408,16 @@ void warn_on_inaccessible(const char *path) warning(_("unable to access '%s': %s"), path, strerror(errno)); } +static int access_error_is_ok(int err, unsigned flag) +{ + return errno == ENOENT || errno == ENOTDIR || + ((flag & ACCESS_EACCES_OK) && errno == EACCES); +} + int access_or_warn(const char *path, int mode, unsigned flag) { int ret = access(path, mode); - if (ret && errno != ENOENT && errno != ENOTDIR && - (!(flag & ACCESS_EACCES_OK) || errno != EACCES)) + if (ret && !access_error_is_ok(errno, flag)) warn_on_inaccessible(path); return ret; } @@ -420,8 +425,7 @@ int access_or_warn(const char *path, int mode, unsigned flag) int access_or_die(const char *path, int mode, unsigned flag) { int ret = access(path, mode); - if (ret && errno != ENOENT && errno != ENOTDIR && - (!(flag & ACCESS_EACCES_OK) || errno != EACCES)) + if (ret && !access_error_is_ok(errno, flag)) die_errno(_("unable to access '%s'"), path); return ret; }
-- 1.8.2.1