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use crate::errors::{Context, SdError};
use nix::errno::Errno;
use nix::fcntl::*;
use nix::sys::memfd::MemFdCreateFlag;
use nix::sys::socket::{sendmsg, ControlMessage, MsgFlags, UnixAddr};
use nix::sys::stat::{fstat, FileStat};
use once_cell::sync::OnceCell;
use std::collections::HashMap;
use std::ffi::{CStr, CString, OsStr};
use std::fs::File;
use std::io::prelude::*;
use std::os::unix::io::AsRawFd;
use std::os::unix::net::UnixDatagram;
use std::os::unix::prelude::AsFd;
use std::os::unix::prelude::FromRawFd;
use std::os::unix::prelude::RawFd;
use std::str::FromStr;
/// Default path of the systemd-journald `AF_UNIX` datagram socket.
pub static SD_JOURNAL_SOCK_PATH: &str = "/run/systemd/journal/socket";
/// The shared socket to journald.
static SD_SOCK: OnceCell<UnixDatagram> = OnceCell::new();
/// Well-known field names. Their validity is covered in tests.
const PRIORITY: ValidField = ValidField::unchecked("PRIORITY");
const MESSAGE: ValidField = ValidField::unchecked("MESSAGE");
/// Trait for checking the type of a file descriptor.
/// Log priority values.
///
/// See `man 3 syslog`.
#[derive(Clone, Copy, Debug)]
#[repr(u8)]
pub enum Priority {
/// System is unusable.
Emergency = 0,
/// Action must be taken immediately.
Alert,
/// Critical condition,
Critical,
/// Error condition.
Error,
/// Warning condition.
Warning,
/// Normal, but significant, condition.
Notice,
/// Informational message.
Info,
/// Debug message.
Debug,
}
impl std::convert::From<Priority> for u8 {
fn from(p: Priority) -> Self {
match p {
Priority::Emergency => 0,
Priority::Alert => 1,
Priority::Critical => 2,
Priority::Error => 3,
Priority::Warning => 4,
Priority::Notice => 5,
Priority::Info => 6,
Priority::Debug => 7,
}
}
}
impl Priority {
fn numeric_level(&self) -> &str {
match self {
Priority::Emergency => "0",
Priority::Alert => "1",
Priority::Critical => "2",
Priority::Error => "3",
Priority::Warning => "4",
Priority::Notice => "5",
Priority::Info => "6",
Priority::Debug => "7",
}
}
}
#[inline(always)]
fn is_valid_char(c: char) -> bool {
c.is_ascii_uppercase() || c.is_ascii_digit() || c == '_'
}
/// The variable name must be in uppercase and consist only of characters,
/// numbers and underscores, and may not begin with an underscore.
///
/// See <https://github.com/systemd/systemd/blob/ed056c560b47f84a0aa0289151f4ec91f786d24a/src/libsystemd/sd-journal/journal-file.c#L1557>
/// for the reference implementation of journal_field_valid.
fn is_valid_field(input: &str) -> bool {
// journald doesn't allow empty fields or fields with more than 64 bytes
if input.is_empty() || 64 < input.len() {
return false;
}
// Fields starting with underscores are protected by journald
if input.starts_with('_') {
return false;
}
// Journald doesn't allow fields to start with digits
if input.starts_with(|c: char| c.is_ascii_digit()) {
return false;
}
input.chars().all(is_valid_char)
}
/// A helper for functions that want to take fields as parameters that have already been validated.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct ValidField<'a> {
field: &'a str,
}
impl<'a> ValidField<'a> {
/// The field value is checked by [[`is_valid_field`]] and a ValidField is returned if true.
fn validate(field: &'a str) -> Option<Self> {
if is_valid_field(field) {
Some(Self { field })
} else {
None
}
}
/// Allows for the construction of a potentially invalid ValidField.
///
/// Since [[`ValidField::is_valid_field`]] cannot reasonably be const, this allows for the
/// construction of known valid field names at compile time. It's expected that the validity is
/// confirmed in tests by [[`ValidField::validate_unchecked`]].
const fn unchecked(field: &'a str) -> Self {
Self { field }
}
/// Converts to a byte slice.
fn as_bytes(&self) -> &'a [u8] {
self.field.as_bytes()
}
/// Returns the length in bytes.
fn len(&self) -> usize {
self.field.len()
}
/// Validates an object created using [[`ValidField::unchecked`]].
///
/// Every unchecked field should have a corresponding test that calls this.
#[cfg(test)]
fn validate_unchecked(&self) -> bool {
is_valid_field(self.field)
}
}
/// Add `field` and `payload` to journal fields `data` with explicit length encoding.
///
/// Write
///
/// 1. the field name,
/// 2. an ASCII newline,
/// 3. the payload size as LE encoded 64 bit integer,
/// 4. the payload, and
/// 5. a final ASCII newline
///
/// to `data`.
///
/// See <https://systemd.io/JOURNAL_NATIVE_PROTOCOL/> for details.
fn add_field_and_payload_explicit_length(data: &mut Vec<u8>, field: ValidField, payload: &str) {
let encoded_len = (payload.len() as u64).to_le_bytes();
// Bump the capacity to avoid multiple allocations during the extend/push calls. The 2 is for
// the newline characters.
data.reserve(field.len() + encoded_len.len() + payload.len() + 2);
data.extend(field.as_bytes());
data.push(b'\n');
data.extend(encoded_len);
data.extend(payload.as_bytes());
data.push(b'\n');
}
/// Add a journal `field` and its `payload` to journal fields `data` with appropriate encoding.
///
/// If `payload` does not contain a newline character use the simple journal field encoding, and
/// write the field name and the payload separated by `=` and suffixed by a final new line.
///
/// Otherwise encode the payload length explicitly with [[`add_field_and_payload_explicit_length`]].
///
/// See <https://systemd.io/JOURNAL_NATIVE_PROTOCOL/> for details.
fn add_field_and_payload(data: &mut Vec<u8>, field: ValidField, payload: &str) {
if payload.contains('\n') {
add_field_and_payload_explicit_length(data, field, payload);
} else {
// If payload doesn't contain an newline directly write the field name and the payload. Bump
// the capacity to avoid multiple allocations during extend/push calls. The 2 is for the
// two pushed bytes.
data.reserve(field.len() + payload.len() + 2);
data.extend(field.as_bytes());
data.push(b'=');
data.extend(payload.as_bytes());
data.push(b'\n');
}
}
/// Send a message with structured properties to the journal.
///
/// The PRIORITY or MESSAGE fields from the vars iterator are always ignored in favour of the priority and message arguments.
pub fn journal_send<K, V>(
priority: Priority,
msg: &str,
vars: impl Iterator<Item = (K, V)>,
) -> Result<(), SdError>
where
K: AsRef<str>,
V: AsRef<str>,
{
let sock = SD_SOCK
.get_or_try_init(UnixDatagram::unbound)
.context("failed to open datagram socket")?;
let mut data = Vec::new();
add_field_and_payload(&mut data, PRIORITY, priority.numeric_level());
add_field_and_payload(&mut data, MESSAGE, msg);
for (ref k, ref v) in vars {
if let Some(field) = ValidField::validate(k.as_ref()) {
if field != PRIORITY && field != MESSAGE {
add_field_and_payload(&mut data, field, v.as_ref())
}
}
}
// Message sending logic:
// * fast path: data within datagram body.
// * slow path: data in a sealed memfd, which is sent as an FD in ancillary data.
//
// Maximum data size is system dependent, thus this always tries the fast path and
// falls back to the slow path if the former fails with `EMSGSIZE`.
match sock.send_to(&data, SD_JOURNAL_SOCK_PATH) {
Ok(x) => Ok(x),
// `EMSGSIZE` (errno code 90) means the message was too long for a UNIX socket,
Err(ref err) if err.raw_os_error() == Some(90) => {
send_memfd_payload(sock, &data).context("sending with memfd failed")
}
Err(e) => Err(e).context("send_to failed"),
}
.map(|_| ())
.with_context(|| format!("failed to print to journal at '{}'", SD_JOURNAL_SOCK_PATH))
}
/// Print a message to the journal with the given priority.
pub fn journal_print(priority: Priority, msg: &str) -> Result<(), SdError> {
let map: HashMap<&str, &str> = HashMap::new();
journal_send(priority, msg, map.iter())
}
// Implementation of memfd_create() using a syscall instead of calling the libc
// function.
//
// The memfd_create() function is only available in glibc >= 2.27 (and other
// libc implementations). To support older versions of glibc, we perform a raw
// syscall (this will fail in Linux < 3.17, where the syscall was not
// available).
//
// nix::sys::memfd::memfd_create chooses at compile time between calling libc
// and performing a syscall, since platforms such as Android and uclibc don't
// have memfd_create() in libc. Here we always use the syscall.
fn memfd_create(name: &CStr, flags: MemFdCreateFlag) -> Result<File, Errno> {
unsafe {
let res = libc::syscall(libc::SYS_memfd_create, name.as_ptr(), flags.bits());
Errno::result(res).map(|r| {
// SAFETY: `memfd_create` just returned this FD, so we own it now.
File::from_raw_fd(r as RawFd)
})
}
}
/// Send an overlarge payload to systemd-journald socket.
///
/// This is a slow-path for sending a large payload that could not otherwise fit
/// in a UNIX datagram. Payload is thus written to a memfd, which is sent as ancillary
/// data.
fn send_memfd_payload(sock: &UnixDatagram, data: &[u8]) -> Result<usize, SdError> {
let memfd = {
let fdname = &CString::new("libsystemd-rs-logging").context("unable to create cstring")?;
let mut file = memfd_create(fdname, MemFdCreateFlag::MFD_ALLOW_SEALING)
.context("unable to create memfd")?;
file.write_all(data).context("failed to write to memfd")?;
file
};
// Seal the memfd, so that journald knows it can safely mmap/read it.
fcntl(memfd.as_raw_fd(), FcntlArg::F_ADD_SEALS(SealFlag::all()))
.context("unable to seal memfd")?;
let fds = &[memfd.as_raw_fd()];
let ancillary = [ControlMessage::ScmRights(fds)];
let path = UnixAddr::new(SD_JOURNAL_SOCK_PATH).context("unable to create new unix address")?;
sendmsg(
sock.as_raw_fd(),
&[],
&ancillary,
MsgFlags::empty(),
Some(&path),
)
.context("sendmsg failed")?;
// Close our side of the memfd after we send it to systemd.
drop(memfd);
Ok(data.len())
}
/// A systemd journal stream.
#[derive(Debug, Eq, PartialEq)]
pub struct JournalStream {
/// The device number of the journal stream.
device: libc::dev_t,
/// The inode number of the journal stream.
inode: libc::ino_t,
}
impl JournalStream {
/// Parse the device and inode number from a systemd journal stream specification.
///
/// See also [`JournalStream::from_env()`].
pub(crate) fn parse<S: AsRef<OsStr>>(value: S) -> Result<Self, SdError> {
let s = value.as_ref().to_str().with_context(|| {
format!(
"Failed to parse journal stream: Value {:?} not UTF-8 encoded",
value.as_ref()
)
})?;
let (device_s, inode_s) =
s.find(':')
.map(|i| (&s[..i], &s[i + 1..]))
.with_context(|| {
format!(
"Failed to parse journal stream: Missing separator ':' in value '{}'",
s
)
})?;
let device = libc::dev_t::from_str(device_s).with_context(|| {
format!(
"Failed to parse journal stream: Device part is not a number '{}'",
device_s
)
})?;
let inode = libc::ino_t::from_str(inode_s).with_context(|| {
format!(
"Failed to parse journal stream: Inode part is not a number '{}'",
inode_s
)
})?;
Ok(JournalStream { device, inode })
}
/// Parse the device and inode number of the systemd journal stream denoted by the given environment variable.
pub(crate) fn from_env_impl<S: AsRef<OsStr>>(key: S) -> Result<Self, SdError> {
Self::parse(std::env::var_os(&key).with_context(|| {
format!(
"Failed to parse journal stream: Environment variable {:?} unset",
key.as_ref()
)
})?)
}
/// Parse the device and inode number of the systemd journal stream denoted by the default `$JOURNAL_STREAM` variable.
///
/// These values are extracted from `$JOURNAL_STREAM`, and consists of the device and inode
/// numbers of the systemd journal stream, separated by `:`.
pub fn from_env() -> Result<Self, SdError> {
Self::from_env_impl("JOURNAL_STREAM")
}
/// Get the journal stream that would correspond to the given file descriptor.
///
/// Return a journal stream struct containing the device and inode number of the given file descriptor.
pub fn from_fd<F: AsFd>(fd: F) -> std::io::Result<Self> {
fstat(fd.as_fd().as_raw_fd())
.map_err(Into::into)
.map(Into::into)
}
}
impl From<FileStat> for JournalStream {
fn from(stat: FileStat) -> Self {
Self {
device: stat.st_dev,
inode: stat.st_ino,
}
}
}
/// Whether this process can be automatically upgraded to native journal logging.
///
/// Inspects the `$JOURNAL_STREAM` environment variable and compares the device and inode
/// numbers in this variable against the stderr file descriptor.
///
/// Return `true` if they match, and `false` otherwise (or in case of any IO error).
///
/// For services normally logging to stderr but also supporting systemd-style structured
/// logging, it is recommended to perform this check and then upgrade to the native systemd
/// journal protocol if possible.
///
/// See section “Automatic Protocol Upgrading” in [systemd documentation][1] for more information.
///
/// [1]: https://systemd.io/JOURNAL_NATIVE_PROTOCOL/#automatic-protocol-upgrading
pub fn connected_to_journal() -> bool {
JournalStream::from_env().map_or(false, |env_stream| {
JournalStream::from_fd(std::io::stderr()).map_or(false, |o| o == env_stream)
})
}
#[cfg(test)]
mod tests {
use super::*;
fn ensure_journald_socket() -> bool {
match std::fs::metadata(SD_JOURNAL_SOCK_PATH) {
Ok(_) => true,
Err(_) => {
eprintln!(
"skipped, journald socket not found at '{}'",
SD_JOURNAL_SOCK_PATH
);
false
}
}
}
const FOO: ValidField = ValidField::unchecked("FOO");
#[test]
fn test_priority_numeric_level_matches_to_string() {
let priorities = [
Priority::Emergency,
Priority::Alert,
Priority::Critical,
Priority::Error,
Priority::Warning,
Priority::Notice,
Priority::Info,
Priority::Debug,
];
for priority in priorities.into_iter() {
assert_eq!(&(u8::from(priority)).to_string(), priority.numeric_level());
}
}
#[test]
fn test_journal_print_simple() {
if !ensure_journald_socket() {
return;
}
journal_print(Priority::Info, "TEST LOG!").unwrap();
}
#[test]
fn test_journal_print_large_buffer() {
if !ensure_journald_socket() {
return;
}
let data = "A".repeat(212995);
journal_print(Priority::Debug, &data).unwrap();
}
#[test]
fn test_journal_send_simple() {
if !ensure_journald_socket() {
return;
}
let mut map: HashMap<&str, &str> = HashMap::new();
map.insert("TEST_JOURNALD_LOG1", "foo");
map.insert("TEST_JOURNALD_LOG2", "bar");
journal_send(Priority::Info, "Test Journald Log", map.iter()).unwrap()
}
#[test]
fn test_journal_skip_fields() {
if !ensure_journald_socket() {
return;
}
let mut map: HashMap<&str, &str> = HashMap::new();
let priority = format!("{}", u8::from(Priority::Warning));
map.insert("TEST_JOURNALD_LOG3", "result");
map.insert("PRIORITY", &priority);
map.insert("MESSAGE", "Duplicate value");
journal_send(Priority::Info, "Test Skip Fields", map.iter()).unwrap()
}
#[test]
fn test_predeclared_fields_are_valid() {
assert!(PRIORITY.validate_unchecked());
assert!(MESSAGE.validate_unchecked());
assert!(FOO.validate_unchecked());
}
#[test]
fn test_is_valid_field_lowercase_invalid() {
let field = "test";
assert!(ValidField::validate(field).is_none());
}
#[test]
fn test_is_valid_field_uppercase_non_ascii_invalid() {
let field = "TRÖT";
assert!(ValidField::validate(field).is_none());
}
#[test]
fn test_is_valid_field_uppercase_valid() {
let field = "TEST";
assert_eq!(
ValidField::validate(field).unwrap().as_bytes(),
field.as_bytes()
);
}
#[test]
fn test_is_valid_field_uppercase_non_alpha_invalid() {
let field = "TE!ST";
assert!(ValidField::validate(field).is_none());
}
#[test]
fn test_is_valid_field_uppercase_leading_underscore_invalid() {
let field = "_TEST";
assert!(ValidField::validate(field).is_none());
}
#[test]
fn test_is_valid_field_uppercase_leading_digit_invalid() {
let field = "1TEST";
assert!(ValidField::validate(field).is_none());
}
#[test]
fn add_field_and_payload_explicit_length_simple() {
let mut data = Vec::new();
add_field_and_payload_explicit_length(&mut data, FOO, "BAR");
assert_eq!(
data,
vec![b'F', b'O', b'O', b'\n', 3, 0, 0, 0, 0, 0, 0, 0, b'B', b'A', b'R', b'\n']
);
}
#[test]
fn add_field_and_payload_explicit_length_internal_newline() {
let mut data = Vec::new();
add_field_and_payload_explicit_length(&mut data, FOO, "B\nAR");
assert_eq!(
data,
vec![b'F', b'O', b'O', b'\n', 4, 0, 0, 0, 0, 0, 0, 0, b'B', b'\n', b'A', b'R', b'\n']
);
}
#[test]
fn add_field_and_payload_explicit_length_trailing_newline() {
let mut data = Vec::new();
add_field_and_payload_explicit_length(&mut data, FOO, "BAR\n");
assert_eq!(
data,
vec![b'F', b'O', b'O', b'\n', 4, 0, 0, 0, 0, 0, 0, 0, b'B', b'A', b'R', b'\n', b'\n']
);
}
#[test]
fn add_field_and_payload_simple() {
let mut data = Vec::new();
add_field_and_payload(&mut data, FOO, "BAR");
assert_eq!(data, "FOO=BAR\n".as_bytes());
}
#[test]
fn add_field_and_payload_internal_newline() {
let mut data = Vec::new();
add_field_and_payload(&mut data, FOO, "B\nAR");
assert_eq!(
data,
vec![b'F', b'O', b'O', b'\n', 4, 0, 0, 0, 0, 0, 0, 0, b'B', b'\n', b'A', b'R', b'\n']
);
}
#[test]
fn add_field_and_payload_trailing_newline() {
let mut data = Vec::new();
add_field_and_payload(&mut data, FOO, "BAR\n");
assert_eq!(
data,
vec![b'F', b'O', b'O', b'\n', 4, 0, 0, 0, 0, 0, 0, 0, b'B', b'A', b'R', b'\n', b'\n']
);
}
#[test]
fn journal_stream_from_fd_does_not_claim_ownership_of_fd() {
// Just get hold of some open file which we know exists and can be read by the current user.
let file = File::open(file!()).unwrap();
let journal_stream = JournalStream::from_fd(&file).unwrap();
assert_ne!(journal_stream.device, 0);
assert_ne!(journal_stream.inode, 0);
// Easy way to check if a file descriptor is still open, see https://stackoverflow.com/a/12340730/355252
let result = fcntl(file.as_raw_fd(), FcntlArg::F_GETFD);
assert!(
result.is_ok(),
"File descriptor not valid anymore after JournalStream::from_fd: {:?}",
result,
);
}
}