ztmux 0.1.0

// Copyright (c) 2021 Holland Schutte, Jayson Morberg
// Copyright (c) 2021 Dallas Lyons <dallasdlyons@gmail.com>
//
// Permission to use, copy, modify, and distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
// IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
// OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
use crate::libc::{getpwuid, getuid};
use crate::*;

bitflags::bitflags! {
    #[repr(transparent)]
    #[derive(Eq, PartialEq)]
    pub struct server_acl_user_flags: i32 {
        const SERVER_ACL_READONLY = 0x1;
    }
}

pub struct server_acl_user {
    pub uid: uid_t,

    pub flags: server_acl_user_flags,

    pub entry: rb_entry<server_acl_user>,
}

/// C `vendor/tmux/server-acl.c:42`: `static int server_acl_cmp(struct server_acl_entry *entry1, struct server_acl_entry *entry2)`
pub fn server_acl_cmp(user1: &server_acl_user, user2: &server_acl_user) -> cmp::Ordering {
    user1.uid.cmp(&user2.uid)
}

pub type server_acl_entries = rb_head<server_acl_user>;
static mut SERVER_ACL_ENTRIES: server_acl_entries = unsafe { zeroed() };

RB_GENERATE!(
    server_acl_entries,
    server_acl_user,
    entry,
    discr_entry,
    server_acl_cmp
);

/// C `vendor/tmux/server-acl.c:112`: `void server_acl_init(void)`
pub unsafe fn server_acl_init() {
    unsafe {
        rb_init(&raw mut SERVER_ACL_ENTRIES);

        if getuid() != 0 {
            server_acl_user_allow(0);
        }
        server_acl_user_allow(getuid());
    }
}

pub unsafe fn server_acl_user_find(uid: uid_t) -> *mut server_acl_user {
    unsafe {
        let mut find: server_acl_user = server_acl_user { uid, ..zeroed() };

        rb_find::<_, _>(&raw mut SERVER_ACL_ENTRIES, &raw mut find)
    }
}

/// C `vendor/tmux/server-acl.c:130`: `void server_acl_display(struct cmdq_item *item)`
pub unsafe fn server_acl_display(item: *mut cmdq_item) {
    unsafe {
        // server_acl_entries
        for loop_ in rb_foreach(&raw mut SERVER_ACL_ENTRIES).map(NonNull::as_ptr) {
            if (*loop_).uid == 0 {
                continue;
            }
            let pw = getpwuid((*loop_).uid);
            let name: *const u8 = if !pw.is_null() {
                (*pw).pw_name.cast()
            } else {
                c!("unknown")
            };
            if (*loop_).flags == server_acl_user_flags::SERVER_ACL_READONLY {
                cmdq_print!(item, "{} (R)", _s(name));
            } else {
                cmdq_print!(item, "{} (W)", _s(name));
            }
        }
    }
}

pub unsafe fn server_acl_user_allow(uid: uid_t) {
    unsafe {
        let mut user = server_acl_user_find(uid);
        if user.is_null() {
            user = xcalloc1();
            (*user).uid = uid;
            // server_acl_entries
            rb_insert(&raw mut SERVER_ACL_ENTRIES, user);
        }
    }
}

pub unsafe fn server_acl_user_deny(uid: uid_t) {
    unsafe {
        let user = server_acl_user_find(uid);
        if !user.is_null() {
            // server_acl_entries
            rb_remove(&raw mut SERVER_ACL_ENTRIES, user);
            free_(user);
        }
    }
}

pub unsafe fn server_acl_user_allow_write(mut uid: uid_t) {
    unsafe {
        let user = server_acl_user_find(uid);
        if user.is_null() {
            return;
        }
        (*user).flags &= !server_acl_user_flags::SERVER_ACL_READONLY;

        for c in tailq_foreach(&raw mut CLIENTS).map(NonNull::as_ptr) {
            uid = proc_get_peer_uid((*c).peer);
            if uid != -1i32 as uid_t && uid == (*user).uid {
                (*c).flags &= !client_flag::READONLY;
            }
        }
    }
}

pub unsafe fn server_acl_user_deny_write(mut uid: uid_t) {
    unsafe {
        let user = server_acl_user_find(uid);
        if user.is_null() {
            return;
        }
        (*user).flags |= server_acl_user_flags::SERVER_ACL_READONLY;

        for c in tailq_foreach(&raw mut CLIENTS).map(NonNull::as_ptr) {
            uid = proc_get_peer_uid((*c).peer);
            if uid != -1i32 as uid_t && uid == (*user).uid {
                (*c).flags &= !client_flag::READONLY;
            }
        }
    }
}

/// C `vendor/tmux/server-acl.c:222`: `int server_acl_join(struct client *c)`
pub unsafe fn server_acl_join(c: *mut client) -> c_int {
    unsafe {
        let uid = proc_get_peer_uid((*c).peer);
        if uid == -1i32 as uid_t {
            return 0;
        }

        let user = server_acl_user_find(uid);
        if user.is_null() {
            return 0;
        }
        if (*user)
            .flags
            .contains(server_acl_user_flags::SERVER_ACL_READONLY)
        {
            (*c).flags |= client_flag::READONLY;
        }
        1
    }
}

pub unsafe fn server_acl_get_uid(user: *mut server_acl_user) -> uid_t {
    unsafe { (*user).uid }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::sync::Mutex;

    // SERVER_ACL_ENTRIES is a single process-global RB tree (server-acl.c:56).
    // Cargo runs tests on parallel threads that all share it, so every test
    // holds this mutex for its whole body and drains the tree on entry/exit so
    // siblings never observe each other's entries. We also use unique high UIDs
    // that cannot collide with the real getuid()/0 entries.
    static ACL_LOCK: Mutex<()> = Mutex::new(());

    // Remove and free every entry currently in the tree so the global state is
    // clean. Mirrors server_acl_user_deny (server-acl.c:178) for each uid.
    unsafe fn drain_all() {
        unsafe {
            loop {
                let min = rb_min::<server_acl_user, discr_entry>(&raw mut SERVER_ACL_ENTRIES);
                if min.is_null() {
                    break;
                }
                rb_remove(&raw mut SERVER_ACL_ENTRIES, min);
                free_(min);
            }
        }
    }

    struct Guard<'a>(#[allow(dead_code)] std::sync::MutexGuard<'a, ()>);
    impl Drop for Guard<'_> {
        fn drop(&mut self) {
            unsafe { drain_all() };
        }
    }
    fn setup() -> Guard<'static> {
        let g = ACL_LOCK.lock().unwrap_or_else(|e| e.into_inner());
        unsafe {
            rb_init(&raw mut SERVER_ACL_ENTRIES);
            drain_all();
        }
        Guard(g)
    }

    // server_acl_cmp (server-acl.c:41) orders purely by uid. The Rust port has
    // no group flag, so it is a straight uid comparison.
    #[test]
    fn test_server_acl_cmp_orders_by_uid() {
        let a = server_acl_user {
            uid: 5,
            flags: server_acl_user_flags::empty(),
            entry: unsafe { zeroed() },
        };
        let b = server_acl_user {
            uid: 10,
            flags: server_acl_user_flags::empty(),
            entry: unsafe { zeroed() },
        };
        assert_eq!(server_acl_cmp(&a, &b), cmp::Ordering::Less);
        assert_eq!(server_acl_cmp(&b, &a), cmp::Ordering::Greater);
        assert_eq!(server_acl_cmp(&a, &a), cmp::Ordering::Equal);
        // Flags must not affect ordering: only uid matters.
        let c = server_acl_user {
            uid: 5,
            flags: server_acl_user_flags::SERVER_ACL_READONLY,
            entry: unsafe { zeroed() },
        };
        assert_eq!(server_acl_cmp(&a, &c), cmp::Ordering::Equal);
    }

    // server_acl_user_allow (server-acl.c:163) inserts a fresh xcalloc'd entry
    // whose uid it sets; server_acl_user_find (server-acl.c:60/122) then locates
    // it. A freshly-allowed entry has flags 0 (write access).
    #[test]
    fn test_allow_then_find() {
        let _g = setup();
        unsafe {
            let uid: uid_t = 900_001;
            assert!(server_acl_user_find(uid).is_null());

            server_acl_user_allow(uid);
            let user = server_acl_user_find(uid);
            assert!(!user.is_null());
            assert_eq!(server_acl_get_uid(user), uid);
            // xcalloc zeroes flags -> not read-only (write access).
            assert!(
                !(*user)
                    .flags
                    .contains(server_acl_user_flags::SERVER_ACL_READONLY)
            );
        }
    }

    // Allowing the same uid twice must not create a second entry
    // (server-acl.c:167 guards on the existing find).
    #[test]
    fn test_allow_is_idempotent() {
        let _g = setup();
        unsafe {
            let uid: uid_t = 900_002;
            server_acl_user_allow(uid);
            let first = server_acl_user_find(uid);
            server_acl_user_allow(uid);
            let second = server_acl_user_find(uid);
            assert!(!first.is_null());
            // Same allocation, i.e. only one entry exists.
            assert_eq!(first, second);
        }
    }

    // server_acl_user_deny (server-acl.c:178) removes the entry; find then
    // returns NULL. Denying an unknown uid is a no-op.
    #[test]
    fn test_deny_removes_and_unknown_is_noop() {
        let _g = setup();
        unsafe {
            let uid: uid_t = 900_003;
            server_acl_user_allow(uid);
            assert!(!server_acl_user_find(uid).is_null());

            server_acl_user_deny(uid);
            assert!(server_acl_user_find(uid).is_null());

            // Denying again / an unknown uid must not crash or resurrect it.
            server_acl_user_deny(uid);
            server_acl_user_deny(900_999);
            assert!(server_acl_user_find(uid).is_null());
        }
    }

    // Unknown uid -> NULL (server-acl.c:67 RB_FIND miss).
    #[test]
    fn test_find_unknown_returns_null() {
        let _g = setup();
        unsafe {
            assert!(server_acl_user_find(900_004).is_null());
        }
    }

    // server_acl_user_deny_write (server-acl.c:205) sets SERVER_ACL_READONLY;
    // server_acl_user_allow_write (server-acl.c:192) clears it. CLIENTS is empty
    // in unit tests so the client-flag loop is a no-op and only the entry flag
    // is observed here.
    #[test]
    fn test_write_flag_toggling() {
        let _g = setup();
        unsafe {
            let uid: uid_t = 900_005;
            server_acl_user_allow(uid);
            let user = server_acl_user_find(uid);
            assert!(!user.is_null());

            // Fresh entry has write access.
            assert!(
                !(*user)
                    .flags
                    .contains(server_acl_user_flags::SERVER_ACL_READONLY)
            );

            server_acl_user_deny_write(uid);
            assert!(
                (*server_acl_user_find(uid))
                    .flags
                    .contains(server_acl_user_flags::SERVER_ACL_READONLY)
            );

            server_acl_user_allow_write(uid);
            assert!(
                !(*server_acl_user_find(uid))
                    .flags
                    .contains(server_acl_user_flags::SERVER_ACL_READONLY)
            );

            // Toggling again is stable.
            server_acl_user_deny_write(uid);
            server_acl_user_deny_write(uid);
            assert!(
                (*server_acl_user_find(uid))
                    .flags
                    .contains(server_acl_user_flags::SERVER_ACL_READONLY)
            );
        }
    }

    // allow_write / deny_write on an unknown uid return early (server-acl.c:197,
    // 210) without inserting anything.
    #[test]
    fn test_write_flag_unknown_uid_is_noop() {
        let _g = setup();
        unsafe {
            let uid: uid_t = 900_006;
            server_acl_user_allow_write(uid);
            assert!(server_acl_user_find(uid).is_null());
            server_acl_user_deny_write(uid);
            assert!(server_acl_user_find(uid).is_null());
        }
    }

    // server_acl_init (server-acl.c:112) always allows uid 0 and getuid(): if
    // getuid()==0 the single allow(getuid()) covers it; otherwise both 0 and
    // getuid() are added explicitly. So after init both must be present.
    #[test]
    fn test_init_allows_root_and_current_uid() {
        let _g = setup();
        unsafe {
            server_acl_init();
            assert!(!server_acl_user_find(0).is_null());
            let me = crate::libc::getuid();
            assert!(!server_acl_user_find(me).is_null());
        }
    }
}