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Add pws-cache extension #156

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Add extension support crate nitrocli-ext
This patch adds the extension support crate nitrocli-ext as a workspace
member. This crate contains useful methods for extensions written in
Rust, providing access to the nitrocli binary and to the nitrokey-rs
library.
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robinkrahl authored and d-e-s-o committed Apr 12, 2021
commit c33be48956992eed8892fe94cd4b8a111fedabc9
1 change: 1 addition & 0 deletions CHANGELOG.md
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@@ -1,5 +1,6 @@
Unreleased
----------
- Introduced extension support crate, `nitrocli-ext`
- Enabled usage of empty PWS slot fields
- Added `NITROCLI_RESOLVED_USB_PATH` environment variable to be used by
extensions
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9 changes: 9 additions & 0 deletions Cargo.lock

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3 changes: 3 additions & 0 deletions Cargo.toml
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Expand Up @@ -82,3 +82,6 @@ version = "1"

[dev-dependencies.tempfile]
version = "3.1"

[workspace]
members = ["ext/*"]
15 changes: 15 additions & 0 deletions ext/ext/Cargo.toml
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# Cargo.toml

# Copyright (C) 2021 The Nitrocli Developers
# SPDX-License-Identifier: GPL-3.0-or-later

[package]
name = "nitrocli-ext"
version = "0.1.0"
authors = ["Robin Krahl <[email protected]>"]
edition = "2018"

[dependencies]
anyhow = "1"
directories = "3"
nitrokey = "0.9"
177 changes: 177 additions & 0 deletions ext/ext/src/lib.rs
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// lib.rs

// Copyright (C) 2020-2021 The Nitrocli Developers
// SPDX-License-Identifier: GPL-3.0-or-later

use std::env;
use std::ffi;
use std::path;
use std::process;

use anyhow::Context as _;

/// A context providing information relevant to `nitrocli` extensions.
#[derive(Debug)]
pub struct Context {
/// Path to the `nitrocli` binary.
nitrocli: ffi::OsString,
/// The path to the USB device that `nitrocli` would connect to, if
/// any.
resolved_usb_path: Option<String>,
/// The verbosity that `nitrocli` should use.
verbosity: Option<u8>,
/// The project directory root to use for the extension in question.
project_dirs: directories::ProjectDirs,
}

impl Context {
/// Create a new `Context` with information provided by `nitrocli`
/// via environment variables.
pub fn from_env() -> anyhow::Result<Self> {
let nitrocli = env::var_os("NITROCLI_BINARY")
.context("NITROCLI_BINARY environment variable not present")
.context("Failed to retrieve nitrocli path")?;

let resolved_usb_path = env::var("NITROCLI_RESOLVED_USB_PATH").ok();

let verbosity = env::var_os("NITROCLI_VERBOSITY")
.context("NITROCLI_VERBOSITY environment variable not present")
.context("Failed to retrieve nitrocli verbosity")?;

let verbosity = if verbosity.len() == 0 {
None
} else {
let verbosity = verbosity
.to_str()
.context("Provided verbosity string is not valid UTF-8")?;
let verbosity = u8::from_str_radix(verbosity, 10).context("Failed to parse verbosity")?;
set_log_level(verbosity);
Some(verbosity)
};

let exe =
env::current_exe().context("Failed to determine the path of the extension executable")?;
let name = exe
.file_name()
.context("Failed to extract the name of the extension executable")?
.to_str()
.context("The name of the extension executable contains non-UTF-8 characters")?;
let project_dirs = directories::ProjectDirs::from("", "", name).with_context(|| {
format!(
"Could not determine the application directories for the {} extension",
name
)
})?;

Ok(Self {
nitrocli,
resolved_usb_path,
verbosity,
project_dirs,
})
}

/// Retrieve `Nitrocli` object for invoking the main `nitrocli`
/// program.
pub fn nitrocli(&self) -> Nitrocli {
Nitrocli::from_context(self)
}

/// Connect to a Nitrokey (or Librem Key) device as `nitrocli` would.
pub fn connect<'mgr>(
&self,
mgr: &'mgr mut nitrokey::Manager,
) -> anyhow::Result<nitrokey::DeviceWrapper<'mgr>> {
if let Some(usb_path) = &self.resolved_usb_path {
mgr.connect_path(usb_path.to_owned()).map_err(From::from)
} else {
// TODO: Improve error message. Unfortunately, we can't easily
// determine whether we have no or more than one (matching)
// device.
Err(anyhow::anyhow!("Could not connect to Nitrokey device"))
}
}

/// Retrieve the path to the directory in which this extension may
/// store cacheable artifacts.
pub fn cache_dir(&self) -> &path::Path {
self.project_dirs.cache_dir()
}
}

// See src/command.rs in nitrocli core.
fn set_log_level(verbosity: u8) {
let log_lvl = match verbosity {
// The error log level is what libnitrokey uses by default. As such,
// there is no harm in us setting that as well when the user did not
// ask for higher verbosity.
0 => nitrokey::LogLevel::Error,
1 => nitrokey::LogLevel::Warning,
2 => nitrokey::LogLevel::Info,
3 => nitrokey::LogLevel::DebugL1,
4 => nitrokey::LogLevel::Debug,
_ => nitrokey::LogLevel::DebugL2,
};
nitrokey::set_log_level(log_lvl);
}

/// A type allowing for convenient invocation of `nitrocli` itself.
#[derive(Debug)]
pub struct Nitrocli {
cmd: process::Command,
}

impl Nitrocli {
/// Create a new `Nitrocli` instance from a `Context`.
fn from_context(ctx: &Context) -> Nitrocli {
Self {
cmd: process::Command::new(&ctx.nitrocli),
}
}

/// Add an argument to the `nitrocli` invocation.
pub fn arg<S>(&mut self, arg: S) -> &mut Nitrocli
where
S: AsRef<ffi::OsStr>,
{
self.cmd.arg(arg);
self
}

/// Add multiple arguments to the `nitrocli` invocation.
pub fn args<I, S>(&mut self, args: I) -> &mut Nitrocli
where
I: IntoIterator<Item = S>,
S: AsRef<ffi::OsStr>,
{
self.cmd.args(args);
self
}

/// Invoke `nitrocli` and retrieve its output as a string.
///
/// Note that any error messages emitted by `nitrocli` will not be
/// intercepted/captured but will directly be passed through. It is
/// recommended that extensions terminate on failure.
pub fn text(&mut self) -> anyhow::Result<String> {
let output = self.cmd.output().context("Failed to invoke nitrocli")?;
// We want additional nitrocli emitted output to be visible to the
// user (typically controlled through -v/--verbose below). Note that
// this means that we will not be able to access this output for
// error reporting purposes.
self.cmd.stderr(process::Stdio::inherit());

if output.status.success() {
String::from_utf8(output.stdout).map_err(From::from)
} else {
Err(anyhow::anyhow!("nitrocli call failed"))
}
}

/// Invoke `nitrocli`.
pub fn spawn(&mut self) -> anyhow::Result<()> {
let mut child = self.cmd.spawn().context("Failed to invoke nitrocli")?;
child.wait().context("Failed to wait on nitrocli")?;
Ok(())
}
}