From 1da53c6d4a72061567430f4ab6b51f1b7fe1079e Mon Sep 17 00:00:00 2001 From: Simon McVittie Date: Fri, 13 Sep 2013 18:50:40 +0100 Subject: [PATCH] _dbus_read_credentials_socket: document where we use each mechanism Bug: https://bugs.freedesktop.org/show_bug.cgi?id=60340 Reviewed-by: Colin Walters --- dbus/dbus-sysdeps-unix.c | 42 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c index 2b66786..0a2b311 100644 --- a/dbus/dbus-sysdeps-unix.c +++ b/dbus/dbus-sysdeps-unix.c @@ -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 } -- 2.7.4