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//
// Syd: rock-solid application kernel
// src/kernel/net/bind.rs: bind(2) handler
//
// Copyright (c) 2023, 2024, 2025, 2026 Ali Polatel <alip@chesswob.org>
//
// SPDX-License-Identifier: GPL-3.0
use std::{net::IpAddr, os::fd::AsRawFd};
use ipnet::IpNet;
use libseccomp::ScmpNotifResp;
use nix::{
errno::Errno,
sys::{
socket::{SockaddrLike, SockaddrStorage},
stat::Mode,
},
};
use crate::{
cache::UnixVal,
compat::{sockaddr_family, AddressFamily},
cookie::{safe_bind, safe_fchdir, safe_getsockname, safe_umask},
fd::SafeOwnedFd,
info,
ip::IpProto,
kernel::net::{get_port, NetAddr},
path::{XPath, XPathBuf, XPathCow, XPathGlob},
proc::proc_umask,
req::UNotifyEventRequest,
sandbox::{Action, AddressPattern, Capability, CidrRule},
wildmatch::MatchMethod,
xfmt,
};
pub(crate) fn handle_bind(
request: &UNotifyEventRequest,
fd: SafeOwnedFd,
addr: (SockaddrStorage, SockaddrStorage),
target: (NetAddr, Option<IpProto>),
allow_safe_bind: bool,
) -> Result<ScmpNotifResp, Errno> {
let req = request.scmpreq;
let (addr, argaddr) = addr;
let (target, sock_proto) = target;
// Prepare environment for UNIX domain sockets.
let umask_set = if let NetAddr::UnixPath(ref root) = target {
let mask = proc_umask(req.pid())?;
// Honour directory for too long sockets.
// Current working directory is per-thread here.
// We cannot resolve symlinks in root or we risk TOCTOU!
let dirfd = root.dir();
safe_fchdir(dirfd)?;
// Set per-thread umask(2) to honour process' umask.
// POSIX ACLs may override this.
safe_umask(mask);
true
} else {
false
};
// All done, call underlying system call.
// bind(2) doesn't follow symlinks in basename.
let result = safe_bind(&fd, &addr);
// Restore umask(2) as necessary.
if umask_set {
safe_umask(Mode::from_bits_retain(0o777));
}
// Check for bind(2) errors.
result?;
// Move domain on bind as necessary.
// This happens before trace/allow_safe_bind, so the address is
// going to be allowlisted in the new domain.
match &target {
NetAddr::Inet(ip, port) => request
.get_sandbox()
.move_on_bind_inet(*ip, *port, sock_proto),
NetAddr::Unix(name) => request.get_sandbox().move_on_bind_unix(name),
NetAddr::UnixPath(root) => request.get_sandbox().move_on_bind_unix(root.abs()),
NetAddr::UnixUnnamed => request
.get_sandbox()
.move_on_bind_unix(XPath::from_bytes(b"!unnamed")),
NetAddr::None => {}
}
// Handle trace/allow_safe_bind and bind_map.
// Ignore errors as bind has already succeeded.
//
// Configure sandbox:
// Remove and re-add the address so repeated binds to the same
// address cannot overflow the vector.
#[expect(clippy::cognitive_complexity)]
let _result = (|fd: SafeOwnedFd, request: &UNotifyEventRequest| -> Result<(), Errno> {
let (addr, port) = match sockaddr_family(&addr) {
AddressFamily::Unix => {
let unix = match target {
NetAddr::UnixPath(root) => {
// Case 1: UNIX domain socket
//
// Handle bind_map after successful bind(2) for UNIX sockets.
// We ignore errors because there's nothing we can do about them.
// We use original address structure for path for getsockname(2).
let _ = request.add_unix(
&fd,
request.scmpreq.pid(),
UnixVal {
addr: argaddr.as_unix_addr().copied(),
..UnixVal::default()
},
);
drop(fd); // Close our copy of the socket.
if !allow_safe_bind {
return Ok(());
}
XPathCow::Owned(root.take())
}
NetAddr::Unix(name) => {
// Case 2: UNIX abstract socket
//
// Handle bind_map after successful bind for UNIX sockets.
// We ignore errors because there's nothing we can do
// about them.
// BindMap is only used for SO_PEERCRED for UNIX abstract sockets.
let _ = request.add_unix(&fd, request.scmpreq.pid(), UnixVal::default());
drop(fd); // Close our copy of the socket.
if !allow_safe_bind {
return Ok(());
}
XPathCow::Owned(name)
}
NetAddr::UnixUnnamed => {
// Case 3: unnamed UNIX socket.
let unix = if addr.as_unix_addr().map_or(0, |addr| addr.len()) as usize
== size_of::<libc::sa_family_t>()
{
// Autobind on abstract UNIX socket.
safe_getsockname::<SockaddrStorage>(fd.as_raw_fd())?
.as_unix_addr()
.ok_or(Errno::EINVAL)?
.as_abstract()
.map(|path| {
// Prefix UNIX abstract sockets with `@' before access check.
// Abstract socket names may contain embedded NUL bytes.
let mut unix = XPathBuf::try_from("@")?;
unix.try_append_bytes(path)?;
Ok::<_, Errno>(unix)
})
.ok_or(Errno::EINVAL)?
.map(XPathCow::Owned)?
} else {
// Use dummy path `!unnamed' for unnamed UNIX sockets.
XPathCow::Borrowed(XPath::from_bytes(b"!unnamed"))
};
// Handle bind_map after successful bind for UNIX sockets.
// We ignore errors because there's nothing we can do
// about them.
// BindMap is only used for SO_PEERCRED for UNIX abstract sockets.
let _ = request.add_unix(&fd, request.scmpreq.pid(), UnixVal::default());
drop(fd); // Close our copy of the socket.
if !allow_safe_bind {
return Ok(());
}
unix
}
NetAddr::None | NetAddr::Inet(..) => {
unreachable!("BUG: non-UNIX target for AF_UNIX bind, report a bug!");
}
};
info!("ctx": "bind", "op": "allow_safe_bind",
"sys": "bind", "pid": request.scmpreq.pid().as_raw(), "unix": &unix,
"msg": xfmt!("add rule `allow/net/connect+{unix}' after bind"));
let mut sandbox = request.get_mut_sandbox();
if let Some(idx) = sandbox.glob_rules.iter().position(|(glob, act, cap)| {
glob.meth == MatchMethod::Literal
&& *act == Action::Allow
&& *cap == Capability::CAP_NET_CONNECT
&& glob.glob.as_bytes() == unix.as_bytes()
}) {
sandbox.glob_rules.remove(idx);
}
return sandbox.glob_rules.push_front((
XPathGlob::new(unix.try_into_owned()?, MatchMethod::Literal),
Action::Allow,
Capability::CAP_NET_CONNECT,
));
}
AddressFamily::Inet => {
if !allow_safe_bind {
return Ok(());
}
let addr = addr.as_sockaddr_in().ok_or(Errno::EINVAL)?;
let mut port = addr.port();
let addr = IpNet::new_assert(IpAddr::V4(addr.ip()), 32);
if port == 0 {
port = get_port(&fd)?;
}
drop(fd); // Close our copy of the socket.
(addr, port)
}
AddressFamily::Inet6 => {
if !allow_safe_bind {
return Ok(());
}
let addr = addr.as_sockaddr_in6().ok_or(Errno::EINVAL)?;
let mut port = addr.port();
let addr = addr.ip();
let addr = if let Some(addr) = addr.to_ipv4_mapped() {
IpNet::new_assert(IpAddr::V4(addr), 32)
} else {
IpNet::new_assert(IpAddr::V6(addr), 128)
};
if port == 0 {
port = get_port(&fd)?;
}
drop(fd); // Close our copy of the socket.
(addr, port)
}
_ => return Ok(()),
};
// Configure sandbox:
// Remove and re-add the address so repeated binds to the
// same address cannot overflow the vector.
let addr = AddressPattern {
addr,
port: port.into(),
proto: None,
};
info!("ctx": "bind", "op": "allow_safe_bind",
"sys": "bind", "pid": request.scmpreq.pid().as_raw(), "rule": &addr,
"msg": xfmt!("add rule `allow/net/connect+{addr}' after bind"));
let rule = CidrRule {
act: Action::Allow,
cap: Capability::CAP_NET_CONNECT,
pat: addr,
};
let mut sandbox = request.get_mut_sandbox();
match sandbox.cidr_rules.iter().position(|r| *r == rule) {
Some(0) => {} // No need to re-add.
Some(idx) => {
sandbox.cidr_rules.remove(idx);
sandbox.cidr_rules.push_front(rule)?;
}
None => sandbox.cidr_rules.push_front(rule)?,
}
// 1. The sandbox lock will be released on drop here.
// 2. The socket fd will be closed on drop here.
Ok(())
})(fd, request);
Ok(request.return_syscall(0))
}