Attachment 74677 Details for Bug 60340 – Unix credentials-passing: add comments explaining how we reach each case

[patch] Unix credentials-passing: add comments explaining how we reach each case

0001-Unix-credentials-passing-add-comments-explaining-how.patch (text/plain), 4.37 KB, created by Simon McVittie on 2013-02-12 13:37:53 UTC

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Creator: Simon McVittie

Created: 2013-02-12 13:37:53 UTC

Size: 4.37 KB

patch

obsolete

>From d2318c75f62aa96818cfe6294205a54ee7fd31b3 Mon Sep 17 00:00:00 2001
>From: Simon McVittie <simon.mcvittie@collabora.co.uk>
>Date: Tue, 12 Feb 2013 13:28:43 +0000
>Subject: [PATCH] Unix credentials-passing: add comments explaining how we
> reach each case
>
>---
> dbus/dbus-sysdeps-unix.c |   61 ++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 61 insertions(+)
>
>diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
>index a031059..0b518dc 100644
>--- a/dbus/dbus-sysdeps-unix.c
>+++ b/dbus/dbus-sysdeps-unix.c
>@@ -1764,6 +1764,14 @@ _dbus_read_credentials_socket  (int              client_fd,
> 
>   {
> #ifdef SO_PEERCRED
>+    /* Supported by at least Linux and OpenBSD.
>+     *
>+     * This mechanism passes the process ID and does not require the peer's
>+     * cooperation, so we prefer it over all others.
>+     *
>+     * Notably, on Linux we never use SCM_CREDENTIALS, because this way is
>+     * less fragile.
>+     */
> #ifdef __OpenBSD__
>     struct sockpeercred cr;
> #else
>@@ -1783,18 +1791,57 @@ _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.
>+     *
>+     * This mechanism requires the peer's cooperation (it has to
>+     * specifically send us a SCM_CREDS message) but it does pass
>+     * the process ID through.
>+     */
>     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 a #elif above this point
>+     * if the mechanism supports passing the process ID, or below
>+     * this point if it does not.
>+     * ------------------------------------------------------------- */
>+
> #elif defined(LOCAL_CREDS)
>+    /* On OSs where _dbus_set_local_creds() is needed, setting that option
>+     * requests that the kernel gives us a struct cmsgcred with type SCM_CREDS.
>+     *
>+     * Supported by NetBSD, QNX. Also supported by FreeBSD, but on FreeBSD
>+     * we prefer the version above, because it tells us the process ID.
>+     *
>+     * If I'm reading FreeBSD man pages correctly, (SOL_SOCKET, SCM_CREDS)
>+     * ancillary messages can have either struct cmsgcred or struct sockcred
>+     * as "payload", depending whether it was sent explicitly via SCM_CREDS or
>+     * received implicitly via LOCAL_CREDS...
>+     */
>     pid_read = DBUS_PID_UNSET;
>     uid_read = cmsg.cred.sc_uid;
>     /* Since we have already got the credentials from this socket, we can
>      * disable its LOCAL_CREDS flag if it was ever set. */
>     _dbus_set_local_creds (client_fd, FALSE);
> #elif defined(HAVE_GETPEEREID)
>+    /* getpeereid() originates from D.J. Bernstein and is fairly
>+     * widely-supported:
>+     *
>+     * - AIX?
>+     * - Blackberry?
>+     * - FreeBSD >= 4.6 (but we prefer cmsgcred)
>+     * - Mac OS X
>+     * - Minix >= 3.1.8
>+     * - MirBSD?
>+     * - OpenBSD >= 3.0
>+     * - QNX? (but we prefer LOCAL_CREDS for some reason)
>+     * - others?
>+     */
>     uid_t euid;
>     gid_t egid;
>     if (getpeereid (client_fd, &euid, &egid) == 0)
>@@ -1806,6 +1853,7 @@ _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. */
>     ucred_t * ucred = NULL;
>     if (getpeerucred (client_fd, &ucred) == 0)
>       {
>@@ -1850,6 +1898,19 @@ _dbus_read_credentials_socket  (int              client_fd,
>     if (ucred != NULL)
>       ucred_free (ucred);
> #else /* !SO_PEERCRED && !HAVE_CMSGCRED && !HAVE_GETPEEREID && !HAVE_GETPEERUCRED */
>+
>+#warning Socket credentials not supported on this Unix OS
>+
>+/* Please add other operating systems known to support at least one of
>+ * the mechanisms above to this list, keeping alphabetical order.
>+ * Everything else is best-effort.
>+ */
>+#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || \
>+    defined(__linux__) || \
>+    defined(__OpenBSD__)
>+# error We really ought to support credentials on this OS!
>+#endif
>+
>     _dbus_verbose ("Socket credentials not supported on this OS\n");
> #endif
>   }
>-- 
>1.7.10.4
>

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Attachments on bug 60340: 74261 | 74677 | 74679 | 74680 | 74698 | 75145 | 85786 | 85787 | 85788 | 85789 | 85790 | 85791

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