Merge #1216

1216: Add UnixCredentials support on FreeBSD/DragonFly r=asomers a=myfreeweb

This allows working with `SCM_CREDS` messages, which are like `SCM_CREDENTIALS` on Linux, but slightly different (always overwritten by the kernel, contain a bit more info — euid and groups).

With this PR, it is possible to write portable code that would use the appropriate message for the platform, but one remaining quirk is that `PassCred` thing still has to be present and `cfg`'d to Linux.

Adding the `SCM_CREDS` constant to libc: rust-lang/libc#1740

Co-authored-by: Greg V <greg@unrelenting.technology>

Author: bors[bot]

CHANGELOG.md

@@ -25,6 +25,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   receive offload (GRO) ([#1209](https://github.com/nix-rust/nix/pull/1209))
 - Added support for `sendmmsg` and `recvmmsg` calls
   (#[1208](https://github.com/nix-rust/nix/pull/1208))
+- Added support for `SCM_CREDS` messages (`UnixCredentials`) on FreeBSD/DragonFly
+  (#[1216](https://github.com/nix-rust/nix/pull/1216))
 
 ### Changed
 - Changed `fallocate` return type from `c_int` to `()` (#[1201](https://github.com/nix-rust/nix/pull/1201))

Cargo.toml

@@ -16,7 +16,7 @@ exclude     = [
 ]
 
 [dependencies]
-libc = { version = "0.2.69", features = [ "extra_traits" ] }
+libc = { git = "https://github.com/rust-lang/libc/", features = [ "extra_traits" ] }
 bitflags = "1.1"
 cfg-if = "0.1.10"
 void = "1.0.2"

src/sys/socket/mod.rs

@@ -189,12 +189,22 @@ cfg_if! {
     if #[cfg(any(target_os = "android", target_os = "linux"))] {
         /// Unix credentials of the sending process.
         ///
-        /// This struct is used with the `SO_PEERCRED` ancillary message for UNIX sockets.
+        /// This struct is used with the `SO_PEERCRED` ancillary message
+        /// and the `SCM_CREDENTIALS` control message for UNIX sockets.
         #[repr(transparent)]
         #[derive(Clone, Copy, Debug, Eq, PartialEq)]
         pub struct UnixCredentials(libc::ucred);
 
         impl UnixCredentials {
+            /// Creates a new instance with the credentials of the current process
+            pub fn new() -> Self {
+                UnixCredentials(libc::ucred {
+                    pid: crate::unistd::getpid().as_raw(),
+                    uid: crate::unistd::getuid().as_raw(),
+                    gid: crate::unistd::getgid().as_raw(),
+                })
+            }
+
             /// Returns the process identifier
             pub fn pid(&self) -> libc::pid_t {
                 self.0.pid
@@ -222,6 +232,46 @@ cfg_if! {
                 self.0
             }
         }
+    } else if #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))] {
+        /// Unix credentials of the sending process.
+        ///
+        /// This struct is used with the `SCM_CREDS` ancillary message for UNIX sockets.
+        #[repr(transparent)]
+        #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+        pub struct UnixCredentials(libc::cmsgcred);
+
+        impl UnixCredentials {
+            /// Returns the process identifier
+            pub fn pid(&self) -> libc::pid_t {
+                self.0.cmcred_pid
+            }
+
+            /// Returns the real user identifier
+            pub fn uid(&self) -> libc::uid_t {
+                self.0.cmcred_uid
+            }
+
+            /// Returns the effective user identifier
+            pub fn euid(&self) -> libc::uid_t {
+                self.0.cmcred_euid
+            }
+
+            /// Returns the real group identifier
+            pub fn gid(&self) -> libc::gid_t {
+                self.0.cmcred_gid
+            }
+
+            /// Returns a list group identifiers (the first one being the effective GID)
+            pub fn groups(&self) -> &[libc::gid_t] {
+                unsafe { slice::from_raw_parts(self.0.cmcred_groups.as_ptr() as *const libc::gid_t, self.0.cmcred_ngroups as _) }
+            }
+        }
+
+        impl From<libc::cmsgcred> for UnixCredentials {
+            fn from(cred: libc::cmsgcred) -> Self {
+                UnixCredentials(cred)
+            }
+        }
     }
 }
 
@@ -369,6 +419,10 @@ pub enum ControlMessageOwned {
     /// [`ControlMessage::ScmCredentials`][#enum.ControlMessage.html#variant.ScmCredentials]
     #[cfg(any(target_os = "android", target_os = "linux"))]
     ScmCredentials(UnixCredentials),
+    /// Received version of
+    /// [`ControlMessage::ScmCreds`][#enum.ControlMessage.html#variant.ScmCreds]
+    #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+    ScmCreds(UnixCredentials),
     /// A message of type `SCM_TIMESTAMP`, containing the time the
     /// packet was received by the kernel.
     ///
@@ -510,6 +564,11 @@ impl ControlMessageOwned {
                 let cred: libc::ucred = ptr::read_unaligned(p as *const _);
                 ControlMessageOwned::ScmCredentials(cred.into())
             }
+            #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+            (libc::SOL_SOCKET, libc::SCM_CREDS) => {
+                let cred: libc::cmsgcred = ptr::read_unaligned(p as *const _);
+                ControlMessageOwned::ScmCreds(cred.into())
+            }
             (libc::SOL_SOCKET, libc::SCM_TIMESTAMP) => {
                 let tv: libc::timeval = ptr::read_unaligned(p as *const _);
                 ControlMessageOwned::ScmTimestamp(TimeVal::from(tv))
@@ -603,6 +662,20 @@ pub enum ControlMessage<'a> {
     /// [`unix(7)`](http://man7.org/linux/man-pages/man7/unix.7.html) man page.
     #[cfg(any(target_os = "android", target_os = "linux"))]
     ScmCredentials(&'a UnixCredentials),
+    /// A message of type `SCM_CREDS`, containing the pid, uid, euid, gid and groups of
+    /// a process connected to the socket.
+    ///
+    /// This is similar to the socket options `LOCAL_CREDS` and `LOCAL_PEERCRED`, but
+    /// requires a process to explicitly send its credentials.
+    ///
+    /// Credentials are always overwritten by the kernel, so this variant does have
+    /// any data, unlike the receive-side
+    /// [`ControlMessageOwned::ScmCreds`][#enum.ControlMessageOwned.html#variant.ScmCreds].
+    ///
+    /// For further information, please refer to the
+    /// [`unix(4)`](https://www.freebsd.org/cgi/man.cgi?query=unix) man page.
+    #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+    ScmCreds,
 
     /// Set IV for `AF_ALG` crypto API.
     ///
@@ -682,6 +755,13 @@ impl<'a> ControlMessage<'a> {
             ControlMessage::ScmCredentials(creds) => {
                 &creds.0 as *const libc::ucred as *const u8
             }
+            #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+            ControlMessage::ScmCreds => {
+                // The kernel overwrites the data, we just zero it
+                // to make sure it's not uninitialized memory
+                unsafe { ptr::write_bytes(cmsg_data, 0, self.len()) };
+                return
+            }
             #[cfg(any(target_os = "android", target_os = "linux"))]
             ControlMessage::AlgSetIv(iv) => {
                 let af_alg_iv = libc::af_alg_iv {
@@ -738,6 +818,10 @@ impl<'a> ControlMessage<'a> {
             ControlMessage::ScmCredentials(creds) => {
                 mem::size_of_val(creds)
             }
+            #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+            ControlMessage::ScmCreds => {
+                mem::size_of::<libc::cmsgcred>()
+            }
             #[cfg(any(target_os = "android", target_os = "linux"))]
             ControlMessage::AlgSetIv(iv) => {
                 mem::size_of::<libc::af_alg_iv>() + iv.len()
@@ -763,6 +847,8 @@ impl<'a> ControlMessage<'a> {
             ControlMessage::ScmRights(_) => libc::SOL_SOCKET,
             #[cfg(any(target_os = "android", target_os = "linux"))]
             ControlMessage::ScmCredentials(_) => libc::SOL_SOCKET,
+            #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+            ControlMessage::ScmCreds => libc::SOL_SOCKET,
             #[cfg(any(target_os = "android", target_os = "linux"))]
             ControlMessage::AlgSetIv(_) | ControlMessage::AlgSetOp(_) |
                 ControlMessage::AlgSetAeadAssoclen(_) => libc::SOL_ALG,
@@ -777,6 +863,8 @@ impl<'a> ControlMessage<'a> {
             ControlMessage::ScmRights(_) => libc::SCM_RIGHTS,
             #[cfg(any(target_os = "android", target_os = "linux"))]
             ControlMessage::ScmCredentials(_) => libc::SCM_CREDENTIALS,
+            #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+            ControlMessage::ScmCreds => libc::SCM_CREDS,
             #[cfg(any(target_os = "android", target_os = "linux"))]
             ControlMessage::AlgSetIv(_) => {
                 libc::ALG_SET_IV

test/sys/test_socket.rs

@@ -752,50 +752,60 @@ pub fn test_sendmsg_empty_cmsgs() {
     }
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(
+    target_os = "android",
+    target_os = "linux",
+    target_os = "freebsd",
+    target_os = "dragonfly",
+))]
 #[test]
 fn test_scm_credentials() {
-    use libc;
     use nix::sys::uio::IoVec;
     use nix::unistd::{close, getpid, getuid, getgid};
     use nix::sys::socket::{socketpair, sendmsg, recvmsg, setsockopt,
                            AddressFamily, SockType, SockFlag,
-                           ControlMessage, ControlMessageOwned, MsgFlags};
+                           ControlMessage, ControlMessageOwned, MsgFlags,
+                           UnixCredentials};
+    #[cfg(any(target_os = "android", target_os = "linux"))]
     use nix::sys::socket::sockopt::PassCred;
 
     let (send, recv) = socketpair(AddressFamily::Unix, SockType::Stream, None, SockFlag::empty())
         .unwrap();
+    #[cfg(any(target_os = "android", target_os = "linux"))]
     setsockopt(recv, PassCred, &true).unwrap();
 
     {
         let iov = [IoVec::from_slice(b"hello")];
-        let cred = libc::ucred {
-            pid: getpid().as_raw(),
-            uid: getuid().as_raw(),
-            gid: getgid().as_raw(),
-        }.into();
+        #[cfg(any(target_os = "android", target_os = "linux"))]
+        let cred = UnixCredentials::new();
+        #[cfg(any(target_os = "android", target_os = "linux"))]
         let cmsg = ControlMessage::ScmCredentials(&cred);
+        #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+        let cmsg = ControlMessage::ScmCreds;
         assert_eq!(sendmsg(send, &iov, &[cmsg], MsgFlags::empty(), None).unwrap(), 5);
         close(send).unwrap();
     }
 
     {
         let mut buf = [0u8; 5];
         let iov = [IoVec::from_mut_slice(&mut buf[..])];
-        let mut cmsgspace = cmsg_space!(libc::ucred);
+        let mut cmsgspace = cmsg_space!(UnixCredentials);
         let msg = recvmsg(recv, &iov, Some(&mut cmsgspace), MsgFlags::empty()).unwrap();
         let mut received_cred = None;
 
         for cmsg in msg.cmsgs() {
-            if let ControlMessageOwned::ScmCredentials(cred) = cmsg {
-                assert!(received_cred.is_none());
-                assert_eq!(cred.pid(), getpid().as_raw());
-                assert_eq!(cred.uid(), getuid().as_raw());
-                assert_eq!(cred.gid(), getgid().as_raw());
-                received_cred = Some(cred);
-            } else {
-                panic!("unexpected cmsg");
-            }
+            let cred = match cmsg {
+                #[cfg(any(target_os = "android", target_os = "linux"))]
+                ControlMessageOwned::ScmCredentials(cred) => cred,
+                #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+                ControlMessageOwned::ScmCreds(cred) => cred,
+                other => panic!("unexpected cmsg {:?}", other),
+            };
+            assert!(received_cred.is_none());
+            assert_eq!(cred.pid(), getpid().as_raw());
+            assert_eq!(cred.uid(), getuid().as_raw());
+            assert_eq!(cred.gid(), getgid().as_raw());
+            received_cred = Some(cred);
         }
         received_cred.expect("no creds received");
         assert_eq!(msg.bytes, 5);