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gpg,common: Make sure that all fd given are valid.

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* common/sysutils.c (gnupg_fd_valid): New function.
* common/sysutils.h (gnupg_fd_valid): New declaration.
* common/logging.c (log_set_file): Use the new function.
* g10/cpr.c (set_status_fd): Likewise.
* g10/gpg.c (main): Likewise.
* g10/keylist.c (read_sessionkey_from_fd): Likewise.
* g10/passphrase.c (set_attrib_fd): Likewise.
* tests/openpgp/Makefile.am (XTESTS): Add the new test.
* tests/openpgp/issue2941.scm: New file.
--

Consider a situation where the user passes "--status-fd 3" but file
descriptor 3 is not open.

During the course of executing the rest of the commands, it's possible
that gpg itself will open some files, and file descriptor 3 will get
allocated.

In this situation, the status information will be appended directly to
whatever file happens to have landed on fd 3 (the trustdb? the
keyring?).

This is a potential data destruction issue for all writable file
descriptor options:

   --status-fd
   --attribute-fd
   --logger-fd

It's also a potential issue for readable file descriptor options, but
the risk is merely weird behavior, and not data corruption:

   --override-session-key-fd
   --passphrase-fd
   --command-fd

Fixes this by checking whether the fd is valid early on before using
it.

GnuPG-bug-id: 2941
Signed-off-by: Justus Winter <justus@g10code.com>
This commit is contained in:
Justus Winter 2017-02-08 13:49:41 +01:00
parent 56aa85f88f
commit 6823ed4658
No known key found for this signature in database
GPG key ID: DD1A52F9DA8C9020
9 changed files with 65 additions and 1 deletions
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5
g10/gpg.c
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@ -3079,6 +3079,8 @@ main (int argc, char **argv)
case oCommandFD:
opt.command_fd = translate_sys2libc_fd_int (pargs.r.ret_int, 0);
if (! gnupg_fd_valid (opt.command_fd))
log_fatal ("command-fd is invalid: %s\n", strerror (errno));
break;
case oCommandFile:
opt.command_fd = open_info_file (pargs.r.ret_str, 0, 1);
@ -5293,6 +5295,9 @@ read_sessionkey_from_fd (int fd)
int i, len;
char *line;
if (! gnupg_fd_valid (fd))
log_fatal ("override-session-key-fd is invalid: %s\n", strerror (errno));
for (line = NULL, i = len = 100; ; i++ )
{
if (i >= len-1 )