isr_cache/

lib.rs

//! # Opinionated cache for OS kernel profiles
//!
//! This crate provides a caching mechanism for profiles generated and used by
//! the [`isr`] crate family. It offers several features to streamline the process
//! of accessing and managing symbol information, including methods for
//! downloading necessary debug symbols for Windows (PDB files) and Linux
//! (DWARF debug info and system map).
//!
//! ## Usage
//!
//! The main component of this crate is the [`IsrCache`] struct.
//!
//! Example of loading a profile from a PDB file using the CodeView information:
//!
//! ```rust
//! use isr::{
//!     download::pdb::CodeView,
//!     cache::{IsrCache, JsonCodec},
//! };
//!
//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
//! # std::env::set_current_dir("../..")?;
//! // Create a new cache instance.
//! let cache = IsrCache::<JsonCodec>::new("cache")?;
//!
//! // Use the CodeView information of the Windows 10.0.18362.356 kernel.
//! let codeview = CodeView {
//!     path: String::from("ntkrnlmp.pdb"),
//!     guid: String::from("ce7ffb00c20b87500211456b3e905c471"),
//! };
//!
//! // Fetch and create (or get existing) the entry.
//! let entry = cache.entry_from_codeview(codeview)?;
//!
//! // Get the profile from the entry.
//! let profile = entry.profile()?;
//! # Ok(())
//! # }
//! ```
//!
//! Example of loading a profile based on a Linux kernel banner:
//!
//! ```rust
//! use isr::cache::{IsrCache, JsonCodec};
//!
//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
//! # std::env::set_current_dir("../..")?;
//! // Create a new cache instance.
//! let cache = IsrCache::<JsonCodec>::new("cache")?;
//!
//! // Use the Linux banner of the Ubuntu 6.8.0-40.40~22.04.3-generic kernel.
//! let banner = "Linux version 6.8.0-40-generic \
//!               (buildd@lcy02-amd64-078) \
//!               (x86_64-linux-gnu-gcc-12 (Ubuntu 12.3.0-1ubuntu1~22.04) \
//!               12.3.0, GNU ld (GNU Binutils for Ubuntu) 2.38) \
//!               #40~22.04.3-Ubuntu SMP PREEMPT_DYNAMIC \
//!               Tue Jul 30 17:30:19 UTC 2 \
//!               (Ubuntu 6.8.0-40.40~22.04.3-generic 6.8.12)";
//!
//! // Fetch and create (or get existing) the entry.
//! // Note that the download of Linux debug symbols may take a while.
//! let entry = cache.entry_from_linux_banner(banner)?;
//!
//! // Get the profile from the entry.
//! let profile = entry.profile()?;
//! # Ok(())
//! # }
//! ```
//!
//! Consult the [`vmi`] crate for more information on how to download debug
//! symbols for introspected VMs.
//!
//! [`isr`]: ../isr/index.html
//! [`vmi`]: ../vmi/index.html

mod codec;
mod error;

use std::{
    fs::File,
    path::{Path, PathBuf},
};

pub use isr_core::Profile;
pub use isr_dl_linux::{
    LinuxBanner, LinuxVersionSignature, UbuntuDownloader, UbuntuVersionSignature,
};
pub use isr_dl_pdb::{CodeView, PdbDownloader};
use memmap2::Mmap;

pub use self::{
    codec::{BincodeCodec, Codec, JsonCodec, MsgpackCodec},
    error::Error,
};

/// An entry in the [`IsrCache`].
pub struct Entry<C>
where
    C: Codec,
{
    /// The path to the profile.
    profile_path: PathBuf,

    /// The raw profile data.
    data: Mmap,

    /// The codec used to encode and decode the profile.
    _codec: std::marker::PhantomData<C>,
}

impl<C> Entry<C>
where
    C: Codec,
{
    /// Creates a new entry from the profile path.
    pub fn new(profile_path: PathBuf) -> Result<Self, Error> {
        let data = unsafe { Mmap::map(&File::open(&profile_path)?)? };
        Ok(Self {
            profile_path,
            data,
            _codec: std::marker::PhantomData,
        })
    }

    /// Returns the path to the profile.
    pub fn profile_path(&self) -> &Path {
        &self.profile_path
    }

    /// Returns the raw profile data.
    pub fn data(&self) -> &[u8] {
        &self.data
    }

    /// Decodes the profile from the entry.
    pub fn profile(&self) -> Result<Profile, C::DecodeError> {
        C::decode(&self.data)
    }
}

/// A cache for OS kernel profiles.
///
/// Manages the download and extraction of necessary debug symbols.
/// Uses a [`Codec`] to encode and decode profiles. The default codec is
/// [`JsonCodec`].
pub struct IsrCache<C = JsonCodec>
where
    C: Codec,
{
    /// The directory where cached profiles are stored.
    directory: PathBuf,

    /// The codec used to encode and decode profiles.
    _codec: std::marker::PhantomData<C>,
}

impl<C> IsrCache<C>
where
    C: Codec,
{
    /// Creates a new `IsrCache` instance, initializing it with the provided
    /// directory. If the directory doesn't exist, it attempts to create it.
    pub fn new(directory: impl Into<PathBuf>) -> Result<Self, Error> {
        let directory = directory.into();
        std::fs::create_dir_all(&directory)?;

        Ok(Self {
            directory,
            _codec: std::marker::PhantomData,
        })
    }

    /// Creates or retrieves a cached profile from a [`CodeView`] debug
    /// information structure.
    ///
    /// If a profile for the given `CodeView` information already exists in
    /// the cache, its path is returned. Otherwise, the necessary PDB file is
    /// downloaded, the profile is generated and stored in the cache, and its
    /// path is returned.
    #[cfg(feature = "pdb")]
    pub fn entry_from_codeview(&self, codeview: CodeView) -> Result<Entry<C>, Error> {
        let path = Path::new(&codeview.path);

        // <cache>/windows/ntkrnlmp.pdb/3844dbb920174967be7aa4a2c20430fa2
        let destination = self
            .directory
            .join("windows")
            .join(path)
            .join(&codeview.guid);

        std::fs::create_dir_all(&destination)?;

        // <cache>/windows/ntkrnlmp.pdb/3844dbb920174967be7aa4a2c20430fa2/ntkrnlmp.pdb
        let pdb_path = destination.join(path);
        if !pdb_path.exists() {
            PdbDownloader::new(codeview.clone())
                .with_output(&pdb_path)
                .download()?;
        }

        // <cache>/windows/ntkrnlmp.pdb/3844dbb920174967be7aa4a2c20430fa2/profile<.ext>
        let profile_path = destination.join("profile").with_extension(C::EXTENSION);

        match File::create_new(&profile_path) {
            Ok(profile_file) => {
                let pdb_file = File::open(&pdb_path)?;
                isr_pdb::create_profile(pdb_file, |profile| C::encode(profile_file, profile))?;
            }
            Err(err) if err.kind() == std::io::ErrorKind::AlreadyExists => {
                tracing::info!(?profile_path, "profile already exists");
            }
            Err(err) => return Err(err.into()),
        }

        Entry::new(profile_path)
    }

    /// Creates or retrieves a cached profile from a PE file.
    ///
    /// Extracts the [`CodeView`] debug information from the PE file and
    /// delegates to [`entry_from_codeview`].
    ///
    /// [`entry_from_codeview`]: Self::entry_from_codeview
    #[cfg(feature = "pdb")]
    pub fn entry_from_pe(&self, path: impl AsRef<Path>) -> Result<Entry<C>, Error> {
        self.entry_from_codeview(CodeView::from_path(path).map_err(isr_dl_pdb::Error::from)?)
    }

    /// Creates or retrieves a cached profile based on a Linux kernel banner.
    ///
    /// Parses the banner to determine the kernel version and downloads the
    /// necessary debug symbols and system map if not present in the cache.
    /// Generates and stores the profile, returning its path.
    #[cfg(feature = "linux")]
    pub fn entry_from_linux_banner(&self, linux_banner: &str) -> Result<Entry<C>, Error> {
        let banner = match LinuxBanner::parse(linux_banner) {
            Some(banner) => banner,
            None => return Err(Error::InvalidBanner),
        };

        let destination_path = match banner.version_signature {
            Some(LinuxVersionSignature::Ubuntu(version_signature)) => {
                self.download_from_ubuntu_version_signature(version_signature)?
            }
            _ => return Err(Error::InvalidBanner),
        };

        let profile_path = destination_path
            .join("profile")
            .with_extension(C::EXTENSION);

        match File::create_new(&profile_path) {
            Ok(profile_file) => {
                let kernel_file = File::open(destination_path.join("vmlinux-dbgsym"))?;
                let systemmap_file = File::open(destination_path.join("System.map"))?;
                isr_dwarf::create_profile(kernel_file, systemmap_file, |profile| {
                    C::encode(profile_file, profile)
                })?;
            }
            Err(err) if err.kind() == std::io::ErrorKind::AlreadyExists => {
                tracing::info!(?profile_path, "profile already exists");
            }
            Err(err) => return Err(err.into()),
        }

        Entry::new(profile_path)
    }

    /// Downloads and extracts the required debug symbols from the Ubuntu
    /// repositories based on the Ubuntu version signature in the Linux banner.
    ///
    /// Returns the path to the directory containing the downloaded and
    /// extracted files.
    #[cfg(feature = "linux")]
    fn download_from_ubuntu_version_signature(
        &self,
        version_signature: UbuntuVersionSignature,
    ) -> Result<PathBuf, isr_dl_linux::Error> {
        let UbuntuVersionSignature {
            release,
            revision,
            kernel_flavour,
            ..
        } = version_signature;

        // <cache>/ubuntu
        let downloader = UbuntuDownloader::new(&release, &revision, &kernel_flavour)
            .with_output_directory(self.directory.join("ubuntu"));

        // <cache>/ubuntu/6.8.0-40.40~22.04.3-generic
        let destination_path = downloader.destination_path();

        // Download only what's necessary.

        // <cache>/ubuntu/6.8.0-40.40~22.04.3-generic/linux-image.deb
        // <cache>/ubuntu/6.8.0-40.40~22.04.3-generic/vmlinuz
        let downloader = match destination_path.join("linux-image.deb").exists() {
            false => downloader
                .download_linux_image_as("linux-image.deb")
                .extract_linux_image_as("vmlinuz"),
            true => {
                tracing::info!("linux-image.deb already exists");
                downloader
            }
        };

        // <cache>/ubuntu/6.8.0-40.40~22.04.3-generic/linux-image-dbgsym.deb
        // <cache>/ubuntu/6.8.0-40.40~22.04.3-generic/vmlinux-dbgsym
        let downloader = match destination_path.join("linux-image-dbgsym.deb").exists() {
            false => downloader
                .download_linux_image_dbgsym_as("linux-image-dbgsym.deb")
                .extract_linux_image_dbgsym_as("vmlinux-dbgsym"),
            true => {
                tracing::info!("linux-image-dbgsym.deb already exists");
                downloader
            }
        };

        // <cache>/ubuntu/6.8.0-40.40~22.04.3-generic/linux-modules.deb
        // <cache>/ubuntu/6.8.0-40.40~22.04.3-generic/System.map
        let downloader = match destination_path.join("linux-modules.deb").exists() {
            false => downloader
                .download_linux_modules_as("linux-modules.deb")
                .extract_systemmap_as("System.map"),
            true => {
                tracing::info!("linux-modules.deb already exists");
                downloader
            }
        };

        match downloader.skip_existing().download() {
            Ok(_paths) => (),
            // UbuntuDownloader::download() returns Err(InvalidOptions) if
            // there's nothing to download.
            Err(isr_dl_linux::ubuntu::Error::InvalidOptions) => {
                tracing::info!("nothing to download");
            }
            Err(err) => return Err(err.into()),
        }

        Ok(destination_path)
    }
}