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_dbus_read_credentials_socket: document where we use each mechanism

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Bug: https://bugs.freedesktop.org/show_bug.cgi?id=60340
Reviewed-by: Colin Walters <walters@verbum.org>
This commit is contained in:
Simon McVittie 2013-09-13 18:50:40 +01:00
parent 4d869cf5c2
commit 1da53c6d4a
1 changed files with 41 additions and 1 deletions
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42
dbus/dbus-sysdeps-unix.c
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@ -1720,6 +1720,14 @@ _dbus_read_credentials_socket (int client_fd,
{
#ifdef SO_PEERCRED
/* Supported by at least Linux and OpenBSD, with minor differences.
*
* This mechanism passes the process ID through and does not require
* the peer's cooperation, so we prefer it over all others. Notably,
* Linux also supports SCM_CREDENTIALS, which is similar to FreeBSD
* SCM_CREDS; it's implemented in GIO, but we don't use it in dbus at all,
* because this is much less fragile.
*/
#ifdef __OpenBSD__
struct sockpeercred cr;
#else
@ -1739,12 +1747,41 @@ _dbus_read_credentials_socket (int client_fd,
cr_len, (int) sizeof (cr), _dbus_strerror (errno));
}
#elif defined(HAVE_CMSGCRED)
/* We only check for HAVE_CMSGCRED, but we're really assuming that the
* presence of that struct implies SCM_CREDS. Supported by at least
* FreeBSD and DragonflyBSD.
*
* This mechanism requires the peer to help us (it has to send us a
* SCM_CREDS message) but it does pass the process ID through,
* which makes it better than getpeereid().
*/
struct cmsgcred *cred;
cred = (struct cmsgcred *) CMSG_DATA (&cmsg.hdr);
pid_read = cred->cmcred_pid;
uid_read = cred->cmcred_euid;
/* ----------------------------------------------------------------
* When adding new mechanisms, please add them above this point
* if they support passing the process ID through, or below if not.
* ---------------------------------------------------------------- */
#elif defined(HAVE_GETPEEREID)
/* getpeereid() originates from D.J. Bernstein and is fairly
* widely-supported. According to a web search, it might be present in
* any/all of:
*
* - AIX?
* - Blackberry?
* - Cygwin
* - FreeBSD 4.6+ (but we prefer SCM_CREDS: it carries the pid)
* - Mac OS X
* - Minix 3.1.8+
* - MirBSD?
* - NetBSD 5.0+ (but LOCAL_PEEREID would be better: it carries the pid)
* - OpenBSD 3.0+ (but we prefer SO_PEERCRED: it carries the pid)
* - QNX?
*/
uid_t euid;
gid_t egid;
if (getpeereid (client_fd, &euid, &egid) == 0)
@ -1756,6 +1793,9 @@ _dbus_read_credentials_socket (int client_fd,
_dbus_verbose ("Failed to getpeereid() credentials: %s\n", _dbus_strerror (errno));
}
#elif defined(HAVE_GETPEERUCRED)
/* Supported in at least Solaris >= 10. It should probably be higher
* up this list, because it carries the pid and we use this code path
* for audit data. */
ucred_t * ucred = NULL;
if (getpeerucred (client_fd, &ucred) == 0)
{
@ -1799,7 +1839,7 @@ _dbus_read_credentials_socket (int client_fd,
}
if (ucred != NULL)
ucred_free (ucred);
#else /* !SO_PEERCRED && !HAVE_CMSGCRED && !HAVE_GETPEEREID && !HAVE_GETPEERUCRED */
#else /* no supported mechanism */
_dbus_verbose ("Socket credentials not supported on this OS\n");
#endif
}