arti/logging.rs
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//! Configure tracing subscribers for Arti
use anyhow::{anyhow, Context, Result};
use derive_builder::Builder;
use fs_mistrust::Mistrust;
use serde::{Deserialize, Serialize};
use std::path::Path;
use std::str::FromStr;
use tor_config::impl_standard_builder;
use tor_config::ConfigBuildError;
use tor_config::{define_list_builder_accessors, define_list_builder_helper};
use tor_config_path::CfgPath;
use tor_error::warn_report;
use tracing::{error, Subscriber};
use tracing_appender::non_blocking::WorkerGuard;
use tracing_subscriber::layer::SubscriberExt;
use tracing_subscriber::prelude::*;
use tracing_subscriber::{filter::Targets, fmt, registry, Layer};
mod time;
/// Structure to hold our logging configuration options
#[derive(Debug, Clone, Builder, Eq, PartialEq)]
#[non_exhaustive] // TODO(nickm) remove public elements when I revise this.
#[builder(build_fn(error = "ConfigBuildError"))]
#[builder(derive(Debug, Serialize, Deserialize))]
pub struct LoggingConfig {
/// Filtering directives that determine tracing levels as described at
/// <https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/targets/struct.Targets.html#impl-FromStr>
///
/// You can override this setting with the -l, --log-level command line parameter.
///
/// Example: "info,tor_proto::channel=trace"
#[builder(default = "default_console_filter()", setter(into, strip_option))]
console: Option<String>,
/// Filtering directives for the journald logger.
///
/// Only takes effect if Arti is built with the `journald` filter.
#[builder(
setter(into),
field(build = r#"tor_config::resolve_option(&self.journald, || None)"#)
)]
journald: Option<String>,
/// Configuration for one or more logfiles.
///
/// The default is not to log to any files.
#[builder_field_attr(serde(default))]
#[builder(sub_builder, setter(custom))]
files: LogfileListConfig,
/// If set to true, we disable safe logging on _all logs_, and store
/// potentially sensitive information at level `info` or higher.
///
/// This can be useful for debugging, but it increases the value of your
/// logs to an attacker. Do not turn this on in production unless you have
/// a good log rotation mechanism.
//
// TODO: Eventually we might want to make this more complex, and add a
// per-log mechanism to turn off unsafe logging. Alternatively, we might do
// that by extending the filter syntax implemented by `tracing` to have an
// "unsafe" flag on particular lines.
#[builder_field_attr(serde(default))]
#[builder(default)]
log_sensitive_information: bool,
/// An approximate granularity with which log times should be displayed.
///
/// This value controls every log time that arti outputs; it doesn't have any
/// effect on times written by other logging programs like `journald`.
///
/// We may round this value up for convenience: For example, if you say
/// "2.5s", we may treat it as if you had said "3s."
///
/// The default is "1s", or one second.
#[builder(default = "std::time::Duration::new(1,0)")]
#[builder_field_attr(serde(default, with = "humantime_serde::option"))]
time_granularity: std::time::Duration,
}
impl_standard_builder! { LoggingConfig }
/// Return a default tracing filter value for `logging.console`.
#[allow(clippy::unnecessary_wraps)]
fn default_console_filter() -> Option<String> {
Some("info".to_owned())
}
/// Local type alias, mostly helpful for derive_builder to DTRT
type LogfileListConfig = Vec<LogfileConfig>;
define_list_builder_helper! {
struct LogfileListConfigBuilder {
files: [LogfileConfigBuilder],
}
built: LogfileListConfig = files;
default = vec![];
}
define_list_builder_accessors! {
struct LoggingConfigBuilder {
pub files: [LogfileConfigBuilder],
}
}
/// Configuration information for an (optionally rotating) logfile.
#[derive(Debug, Builder, Clone, Eq, PartialEq)]
#[builder(derive(Debug, Serialize, Deserialize))]
#[builder(build_fn(error = "ConfigBuildError"))]
pub struct LogfileConfig {
/// How often to rotate the file?
#[builder(default)]
rotate: LogRotation,
/// Where to write the files?
path: CfgPath,
/// Filter to apply before writing
filter: String,
}
impl_standard_builder! { LogfileConfig: !Default }
/// How often to rotate a log file
#[derive(Debug, Default, Clone, Serialize, Deserialize, Copy, Eq, PartialEq)]
#[non_exhaustive]
#[serde(rename_all = "lowercase")]
pub enum LogRotation {
/// Rotate logs daily
Daily,
/// Rotate logs hourly
Hourly,
/// Never rotate the log
#[default]
Never,
}
/// As [`Targets::from_str`], but wrapped in an [`anyhow::Result`].
//
// (Note that we have to use `Targets`, not `EnvFilter`: see comment in
// `setup_logging()`.)
fn filt_from_str_verbose(s: &str, source: &str) -> Result<Targets> {
Targets::from_str(s).with_context(|| format!("in {}", source))
}
/// As filt_from_str_verbose, but treat an absent filter (or an empty string) as
/// None.
fn filt_from_opt_str(s: &Option<String>, source: &str) -> Result<Option<Targets>> {
Ok(match s {
Some(s) if !s.is_empty() => Some(filt_from_str_verbose(s, source)?),
_ => None,
})
}
/// Try to construct a tracing [`Layer`] for logging to stdout.
fn console_layer<S>(config: &LoggingConfig, cli: Option<&str>) -> Result<impl Layer<S>>
where
S: Subscriber + for<'span> tracing_subscriber::registry::LookupSpan<'span>,
{
let timer = time::new_formatter(config.time_granularity);
let filter = cli
.map(|s| filt_from_str_verbose(s, "--log-level command line parameter"))
.or_else(|| filt_from_opt_str(&config.console, "logging.console").transpose())
.unwrap_or_else(|| Ok(Targets::from_str("debug").expect("bad default")))?;
// We used to suppress safe-logging on the console, but we removed that
// feature: we cannot be certain that the console really is volatile. Even
// if isatty() returns true on the console, we can't be sure that the
// terminal isn't saving backlog to disk or something like that.
Ok(fmt::Layer::default().with_timer(timer).with_filter(filter))
}
/// Try to construct a tracing [`Layer`] for logging to journald, if one is
/// configured.
#[cfg(feature = "journald")]
fn journald_layer<S>(config: &LoggingConfig) -> Result<impl Layer<S>>
where
S: Subscriber + for<'span> tracing_subscriber::registry::LookupSpan<'span>,
{
if let Some(filter) = filt_from_opt_str(&config.journald, "logging.journald")? {
Ok(Some(tracing_journald::layer()?.with_filter(filter)))
} else {
// Fortunately, Option<Layer> implements Layer, so we can just return None here.
Ok(None)
}
}
/// Try to construct a non-blocking tracing [`Layer`] for writing data to an
/// optionally rotating logfile.
///
/// On success, return that layer, along with a WorkerGuard that needs to be
/// dropped when the program exits, to flush buffered messages.
fn logfile_layer<S>(
config: &LogfileConfig,
granularity: std::time::Duration,
mistrust: &Mistrust,
) -> Result<(impl Layer<S> + Send + Sync + Sized, WorkerGuard)>
where
S: Subscriber + for<'span> tracing_subscriber::registry::LookupSpan<'span> + Send + Sync,
{
use tracing_appender::{
non_blocking,
rolling::{RollingFileAppender, Rotation},
};
let timer = time::new_formatter(granularity);
let filter = filt_from_str_verbose(&config.filter, "logging.files.filter")?;
let rotation = match config.rotate {
LogRotation::Daily => Rotation::DAILY,
LogRotation::Hourly => Rotation::HOURLY,
_ => Rotation::NEVER,
};
let path = config.path.path()?;
let directory = path.parent().unwrap_or_else(|| Path::new("."));
mistrust.make_directory(directory)?;
let fname = path
.file_name()
.ok_or_else(|| anyhow!("No path for log file"))
.map(Path::new)?;
let appender = RollingFileAppender::new(rotation, directory, fname);
let (nonblocking, guard) = non_blocking(appender);
let layer = fmt::layer()
.with_ansi(false)
.with_writer(nonblocking)
.with_timer(timer)
.with_filter(filter);
Ok((layer, guard))
}
/// Try to construct a tracing [`Layer`] for all of the configured logfiles.
///
/// On success, return that layer along with a list of [`WorkerGuard`]s that
/// need to be dropped when the program exits.
fn logfile_layers<S>(
config: &LoggingConfig,
mistrust: &Mistrust,
) -> Result<(impl Layer<S>, Vec<WorkerGuard>)>
where
S: Subscriber + for<'span> tracing_subscriber::registry::LookupSpan<'span> + Send + Sync,
{
let mut guards = Vec::new();
if config.files.is_empty() {
// As above, we have Option<Layer> implements Layer, so we can return
// None in this case.
return Ok((None, guards));
}
let (layer, guard) = logfile_layer(&config.files[0], config.time_granularity, mistrust)?;
guards.push(guard);
// We have to use a dyn pointer here so we can build up linked list of
// arbitrary depth.
let mut layer: Box<dyn Layer<S> + Send + Sync + 'static> = Box::new(layer);
for logfile in &config.files[1..] {
let (new_layer, guard) = logfile_layer(logfile, config.time_granularity, mistrust)?;
layer = Box::new(layer.and_then(new_layer));
guards.push(guard);
}
Ok((Some(layer), guards))
}
/// Configure a panic handler to send everything to tracing, in addition to our
/// default panic behavior.
fn install_panic_handler() {
// TODO library support: There's a library called `tracing-panic` that
// provides a hook we could use instead, but that doesn't have backtrace
// support. We should consider using it if it gets backtrace support in the
// future. We should also keep an eye on `tracing` to see if it learns how
// to do this for us.
let default_handler = std::panic::take_hook();
std::panic::set_hook(Box::new(move |panic_info| {
// Note that if we were ever to _not_ call this handler,
// we would want to abort on nested panics and !can_unwind cases.
default_handler(panic_info);
// This statement is copied from stdlib.
let msg = match panic_info.payload().downcast_ref::<&'static str>() {
Some(s) => *s,
None => match panic_info.payload().downcast_ref::<String>() {
Some(s) => &s[..],
None => "Box<dyn Any>",
},
};
let backtrace = std::backtrace::Backtrace::force_capture();
match panic_info.location() {
Some(location) => error!("Panic at {}: {}\n{}", location, msg, backtrace),
None => error!("Panic at ???: {}\n{}", msg, backtrace),
};
}));
}
/// Opaque structure that gets dropped when the program is shutting down,
/// after logs are no longer needed. The `Drop` impl flushes buffered messages.
#[cfg_attr(feature = "experimental-api", visibility::make(pub))]
pub(crate) struct LogGuards {
/// The actual list of guards we're returning.
#[allow(unused)]
guards: Vec<WorkerGuard>,
/// A safelog guard, for use if we have decided to disable safe logging.
#[allow(unused)]
safelog_guard: Option<safelog::Guard>,
}
/// Set up logging.
///
/// Note that the returned LogGuard must be dropped precisely when the program
/// quits; they're used to ensure that all the log messages are flushed.
#[cfg_attr(feature = "experimental-api", visibility::make(pub))]
#[cfg_attr(docsrs, doc(cfg(feature = "experimental-api")))]
pub(crate) fn setup_logging(
config: &LoggingConfig,
mistrust: &Mistrust,
cli: Option<&str>,
) -> Result<LogGuards> {
// Important: We have to make sure that the individual layers we add here
// are not filters themselves. That means, for example, that we can't add
// an `EnvFilter` layer unless we want it to apply globally to _all_ layers.
//
// For a bit of discussion on the difference between per-layer filters and filters
// that apply to the entire registry, see
// https://docs.rs/tracing-subscriber/0.3.5/tracing_subscriber/layer/index.html#global-filtering
let registry = registry().with(console_layer(config, cli)?);
#[cfg(feature = "journald")]
let registry = registry.with(journald_layer(config)?);
let (layer, guards) = logfile_layers(config, mistrust)?;
let registry = registry.with(layer);
registry.init();
let safelog_guard = if config.log_sensitive_information {
match safelog::disable_safe_logging() {
Ok(guard) => Some(guard),
Err(e) => {
// We don't need to propagate this error; it isn't the end of
// the world if we were unable to disable safe logging.
warn_report!(e, "Unable to disable safe logging");
None
}
}
} else {
None
};
install_panic_handler();
Ok(LogGuards {
guards,
safelog_guard,
})
}