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Subject: |
mktemp-related race condition in movemail |
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Date: |
Fri, 10 Jun 2011 10:46:47 -0700 |
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User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 |
There is a race condition in lib-src/movemail.c, and some
related bugs. I plan to commit the following patch.
This one has security implications, so I'm filing a bug
report to give others a bigger heads-up.
I found this one via GCC 4.6.0's static analysis.
* movemail.c: Fix race condition and related bugs.
(main) [!MAIL_USE_SYSTEM_LOCK]: Prefer mkstemp to mktemp, as this
fixes some race conditions. Report mkstemp/mktemp errno rather
than a possibly-garbage errno. Reinitialize the template each
time through the loop, as earlier mkstemp/mktemp calls could have
trashed it. Pass 0600 (not 0666) to mktemp, for consistency
with mkstemp; the permissions don't matter anyway.
=== modified file 'lib-src/movemail.c'
--- lib-src/movemail.c 2011-04-16 21:20:25 +0000
+++ lib-src/movemail.c 2011-06-10 17:30:52 +0000
@@ -168,8 +168,9 @@
#ifndef MAIL_USE_SYSTEM_LOCK
struct stat st;
int tem;
- char *lockname, *p;
+ char *lockname;
char *tempname;
+ size_t inname_dirlen;
int desc;
#endif /* not MAIL_USE_SYSTEM_LOCK */
@@ -298,26 +299,38 @@
to address@hidden so we can fix it. */
lockname = concat (inname, ".lock", "");
- tempname = (char *) xmalloc (strlen (inname) + strlen ("EXXXXXX") + 1);
- strcpy (tempname, inname);
- p = tempname + strlen (tempname);
- while (p != tempname && !IS_DIRECTORY_SEP (p[-1]))
- p--;
- *p = 0;
- strcpy (p, "EXXXXXX");
- mktemp (tempname);
- unlink (tempname);
+ for (inname_dirlen = strlen (inname);
+ inname_dirlen && !IS_DIRECTORY_SEP (inname[inname_dirlen - 1]);
+ inname_dirlen--)
+ continue;
+ tempname = (char *) xmalloc (inname_dirlen + sizeof "EXXXXXX");
while (1)
{
/* Create the lock file, but not under the lock file name. */
/* Give up if cannot do that. */
- desc = open (tempname, O_WRONLY | O_CREAT | O_EXCL, 0666);
+
+ memcpy (tempname, inname, inname_dirlen);
+ strcpy (tempname + inname_dirlen, "EXXXXXX");
+#ifdef HAVE_MKSTEMP
+ desc = mkstemp (tempname);
+#else
+ mktemp (tempname);
+ if (!*tempname)
+ desc = -1;
+ else
+ {
+ unlink (tempname);
+ desc = open (tempname, O_WRONLY | O_CREAT | O_EXCL, 0600);
+ }
+#endif
if (desc < 0)
{
+ int mkstemp_errno = errno;
char *message = (char *) xmalloc (strlen (tempname) + 50);
sprintf (message, "creating %s, which would become the lock file",
tempname);
+ errno = mkstemp_errno;
pfatal_with_name (message);
}
close (desc);
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--- Begin Message ---
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Subject: |
Re: bug#8836: Acknowledgement (mktemp-related race condition in movemail) |
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Date: |
Fri, 10 Jun 2011 10:50:58 -0700 |
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User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 |
I committed the fix in bzr 104555 on the trunk.
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