Browse Source

merged inspectors module into files

edition-2021
Lynne Megido 3 months ago
parent
commit
fa49dd9fb5
Signed by: lynnesbian
GPG Key ID: F0A184B5213D9F90
  1. 139
      src/files.rs
  2. 4
      src/findings.rs
  3. 133
      src/inspectors.rs
  4. 1
      src/lib.rs
  5. 2
      src/parameters.rs
  6. 11
      src/tests/mod.rs

139
src/files.rs

@ -1,11 +1,20 @@
use crate::findings::{Findings, ScanError};
use crate::mime_db::MimeDb;
use crate::parameters::ScanOpts;
use crate::{inspectors, MIMEDB};
use crate::MIMEDB;
use std::collections::BTreeSet;
use std::fs::File;
use std::io;
use std::io::{Read, Seek, SeekFrom};
use std::path::Path;
use std::str::FromStr;
use cached::cached;
use cfg_if::cfg_if;
use log::{debug, error};
use mime::Mime;
use mime_guess::from_ext;
use std::collections::BTreeSet;
use std::path::Path;
use walkdir::{DirEntry, WalkDir};
cfg_if! {
@ -84,7 +93,7 @@ pub fn wanted_file(
pub fn scan_file(entry: &DirEntry, canonical_paths: bool) -> Result<Findings, ScanError> {
let path = entry.path();
// try to determine mimetype for this entry
let result = match inspectors::mime_type(MIMEDB.get().unwrap(), path) {
let result = match mime_type(MIMEDB.get().unwrap(), path) {
// an error occurred while trying to read the file
Err(_) => return Err(ScanError::File(path)),
// the file was read successfully, but we were unable to determine its mimetype
@ -94,7 +103,7 @@ pub fn scan_file(entry: &DirEntry, canonical_paths: bool) -> Result<Findings, Sc
};
// set of known extensions for the given mimetype
let known_exts = inspectors::mime_extension_lookup(result.essence_str().into());
let known_exts = mime_extension_lookup(result.essence_str().into());
// file extension for this particular file
let entry_ext = path.extension();
@ -196,3 +205,123 @@ pub fn scan_directory(
Some(entries)
}
}
/// The number of bytes to read initially.
///
/// Rather than reading the entire file all at once into a [`BUF_SIZE`] buffer, it tends to be faster to read a small
/// chunk of the file and trying to identify that, proceeding with the larger buffer if that fails. Many file formats
/// can be identified with the first few dozen bytes, so the "happy path" will likely be taken in the majority of cases.
pub const INITIAL_BUF_SIZE: usize = 128;
/// The number of bytes to read if the file couldn't be identified from its first [`INITIAL_BUF_SIZE`] bytes.
pub const BUF_SIZE: usize = 8192;
/// Tries to identify the mimetype of a file from a given path.
pub fn mime_type<T: MimeDb>(db: &T, path: &Path) -> io::Result<Option<Mime>> {
let mut buffer = [0; INITIAL_BUF_SIZE];
let mut file = File::open(path)?;
// read a small amount to start with
file.read(&mut buffer)?;
let r = db.get_type(&buffer).filter(|mime|
// some mime types should be investigated further, reading up to BUF_SIZE even if they've been determined already
// one such type is XML - there's many more specific types that can be determined by reading further (such as SVG)
mime != &mime::TEXT_XML
// another is ZIP - many file formats (DOCX, ODT, JAR...) are just ZIP files with particular data structures.
// determining that a file is in one of the MS office formats in particular requires looking quite far into the
// file.
&& mime != &Mime::from_str("application/zip").unwrap()
// doc/ppt/xls files are a subset of what's known as an "OLE2 compound document storage", at least according to
// shared-mime-info. if a pre-OOXML era MS office file is scanned and identified as x-ole-storage, reading further
// will allow it to be detected correctly as the appropriate filetype.
&& mime != &Mime::from_str("application/x-ole-storage").unwrap());
if r.is_some() {
return Ok(r);
}
// attempt to read up to the BUF_SIZE bytes of the file.
// we've already read the first 128 bytes into a buffer, but i can't see an obvious way to reuse them in a way that's
// faster than simply moving the seek position back to the start of the file and re-reading the whole BUF_SIZE bytes.
// for example, reading (BUF_SIZE - INITIAL_BUF_SIZE) bytes, then concatenating the original INITIAL_BUF_SIZE buffer
// with this new one would presumably be faster - but it's not. i think it's more expensive to create the iterator,
// collect the contents, etc. i'll have to look into this more. i don't at all doubt that there IS a way to do this
// efficiently, and i can think of a way in principle, but i'm not sure how to express it in a way that is both
// idiomatic/safe and fast.
let mut buffer = [0; BUF_SIZE];
file.seek(SeekFrom::Start(0))?;
file.read(&mut buffer)?;
Ok(db.get_type(&buffer))
}
cached! {
MIMEXT;
fn mime_extension_lookup(essence: String) -> Option<Vec<String>> = {
// Returns a list of known extensions for this mime type, if any.
// This function uses the [Mime]'s "essence" rather than the [Mime] itself - mime_guess::get_mime_extensions ignores
// the type suffix, treating "image/svg+xml" as "image/svg", and thus fails to find any extensions. Passing the
// essence_str (which includes the suffix) fixes this.
// ↑ this is supposed to be a doc comment, but the cached! macro doesn't support that... i would switch to the
// proc_macro version of cached, but it has a huge number of deps :c
let essence = essence.as_str();
let mut exts = mime_guess::get_mime_extensions_str(essence);
if exts.is_none() {
// no matches :c
// mime_guess' database isn't exactly perfect... there are a lot of times where the db will return "some/x-thing"
// but mime_guess only understands "some/thing", or vice-versa.
// so, if there appear to be no extensions, try replacing "some/x-thing" with "some/thing", or "some/thing" with
// "some/x-thing".
if essence.contains("/x-") {
// replace e.g. "application/x-gzip" with "application/gzip"
exts = mime_guess::get_mime_extensions_str(&essence.replace("/x-", "/"));
} else {
// replace e.g. "video/mp2t" with "video/x-mp2t"
exts = mime_guess::get_mime_extensions_str(&essence.replace("/", "/x-"));
}
}
match exts {
Some(exts) => {
let possible_exts: Vec<String> = exts.iter().map(|e| String::from(*e)).collect();
Some(if essence == mime::IMAGE_JPEG.essence_str() {
// possible_exts starts with "jpe", because it's alphabetically before "jpeg" and "jpg". however, jpg/jpeg are
// far more common than jpe, so it makes sense to suggest one of those rather than jpe. to do this, we can
// add "jpg" to the start of the possible_exts list, ensuring that it will be the extension suggested by fif.
[vec![String::from("jpg")], possible_exts].concat()
} else if essence == mime::TEXT_XML.essence_str() || essence == "application/xml" {
// a somewhat similar case arises with XML files - the first suggested extension is "asa", when it should
// (in my opinion) be "xml".
// there's also another problem: SVG files can easily be misidentified as XML files, because they usually
// *are* valid XML - the more whitespace and comments an SVG file begins with, the more bytes must be read
// before it's possible to determine that it's an SVG rather than an XML file. to "fix" this, we can add "svg"
// as a valid extension for XML files, ensuring that SVG files misidentified as XML will still be considered
// to have valid extensions.
// TODO: if a file is detected as application/xml, but it has an extension like "xht" which corresponds to
// "application/xhtml+xml", let it through - in other words, if it's identified as application/xml, but its
// extension is classed as application/*+xml, consider it OK
[vec![String::from("xml"), String::from("svg")], possible_exts].concat()
} else if essence == "application/msword" {
// classic office files considered harmful
vec![String::from("doc"), String::from("xls"), String::from("ppt")]
} else if essence == "application/zip" {
// neither xdg-mime nor infer seem to be able to detect office XML files properly...
[vec![String::from("zip"), String::from("docx"), String::from("xlsx"), String::from("pptx")], possible_exts].concat()
} else if essence == "application/x-ms-dos-executable" {
// both .dll and .exe files are given the same mime type... but you definitely don't want to rename one to the
// other!
[vec![String::from("dll"), String::from("exe")], possible_exts].concat()
} else {
possible_exts
})
},
None => None
}
}
}

4
src/findings.rs

@ -2,7 +2,7 @@ use std::path::{Path, PathBuf};
use mime::Mime;
use crate::inspectors::mime_extension_lookup;
use crate::files::mime_extension_lookup;
use crate::String;
#[cfg(feature = "json")]
@ -37,7 +37,7 @@ impl serde::Serialize for Findings {
}
impl Findings {
pub fn recommended_extension(&self) -> Option<String> {
pub fn recommended_extension(&self) -> Option<std::string::String> {
mime_extension_lookup(self.mime.essence_str().into()).map(|extensions| extensions[0].clone())
}
}

133
src/inspectors.rs

@ -1,133 +0,0 @@
//! Functions for getting the mime type and extension of a file.
use std::fs::File;
use std::io;
use std::io::{Read, Seek, SeekFrom};
use std::path::Path;
use std::str::FromStr;
use cached::cached;
use mime::Mime;
use crate::String;
use crate::MimeDb;
/// The number of bytes to read initially.
///
/// Rather than reading the entire file all at once into a [`BUF_SIZE`] buffer, it tends to be faster to read a small
/// chunk of the file and trying to identify that, proceeding with the larger buffer if that fails. Many file formats
/// can be identified with the first few dozen bytes, so the "happy path" will likely be taken in the majority of cases.
pub const INITIAL_BUF_SIZE: usize = 128;
/// The number of bytes to read if the file couldn't be identified from its first [`INITIAL_BUF_SIZE`] bytes.
pub const BUF_SIZE: usize = 8192;
/// Tries to identify the mimetype of a file from a given path.
pub fn mime_type<T: MimeDb>(db: &T, path: &Path) -> io::Result<Option<Mime>> {
let mut buffer = [0; INITIAL_BUF_SIZE];
let mut file = File::open(path)?;
// read a small amount to start with
file.read(&mut buffer)?;
let r = db.get_type(&buffer).filter(|mime|
// some mime types should be investigated further, reading up to BUF_SIZE even if they've been determined already
// one such type is XML - there's many more specific types that can be determined by reading further (such as SVG)
mime != &mime::TEXT_XML
// another is ZIP - many file formats (DOCX, ODT, JAR...) are just ZIP files with particular data structures.
// determining that a file is in one of the MS office formats in particular requires looking quite far into the
// file.
&& mime != &Mime::from_str("application/zip").unwrap()
// doc/ppt/xls files are a subset of what's known as an "OLE2 compound document storage", at least according to
// shared-mime-info. if a pre-OOXML era MS office file is scanned and identified as x-ole-storage, reading further
// will allow it to be detected correctly as the appropriate filetype.
&& mime != &Mime::from_str("application/x-ole-storage").unwrap());
if r.is_some() {
return Ok(r);
}
// attempt to read up to the BUF_SIZE bytes of the file.
// we've already read the first 128 bytes into a buffer, but i can't see an obvious way to reuse them in a way that's
// faster than simply moving the seek position back to the start of the file and re-reading the whole BUF_SIZE bytes.
// for example, reading (BUF_SIZE - INITIAL_BUF_SIZE) bytes, then concatenating the original INITIAL_BUF_SIZE buffer
// with this new one would presumably be faster - but it's not. i think it's more expensive to create the iterator,
// collect the contents, etc. i'll have to look into this more. i don't at all doubt that there IS a way to do this
// efficiently, and i can think of a way in principle, but i'm not sure how to express it in a way that is both
// idiomatic/safe and fast.
let mut buffer = [0; BUF_SIZE];
file.seek(SeekFrom::Start(0))?;
file.read(&mut buffer)?;
Ok(db.get_type(&buffer))
}
cached! {
MIMEXT;
fn mime_extension_lookup(essence: String) -> Option<Vec<String>> = {
// Returns a list of known extensions for this mime type, if any.
// This function uses the [Mime]'s "essence" rather than the [Mime] itself - mime_guess::get_mime_extensions ignores
// the type suffix, treating "image/svg+xml" as "image/svg", and thus fails to find any extensions. Passing the
// essence_str (which includes the suffix) fixes this.
// ↑ this is supposed to be a doc comment, but the cached! macro doesn't support that... i would switch to the
// proc_macro version of cached, but it has a huge number of deps :c
let essence = essence.as_str();
let mut exts = mime_guess::get_mime_extensions_str(essence);
if exts.is_none() {
// no matches :c
// mime_guess' database isn't exactly perfect... there are a lot of times where the db will return "some/x-thing"
// but mime_guess only understands "some/thing", or vice-versa.
// so, if there appear to be no extensions, try replacing "some/x-thing" with "some/thing", or "some/thing" with
// "some/x-thing".
if essence.contains("/x-") {
// replace e.g. "application/x-gzip" with "application/gzip"
exts = mime_guess::get_mime_extensions_str(&essence.replace("/x-", "/"));
} else {
// replace e.g. "video/mp2t" with "video/x-mp2t"
exts = mime_guess::get_mime_extensions_str(&essence.replace("/", "/x-"));
}
}
match exts {
Some(exts) => {
let possible_exts: Vec<String> = exts.iter().map(|e| String::from(*e)).collect();
Some(if essence == mime::IMAGE_JPEG.essence_str() {
// possible_exts starts with "jpe", because it's alphabetically before "jpeg" and "jpg". however, jpg/jpeg are
// far more common than jpe, so it makes sense to suggest one of those rather than jpe. to do this, we can
// add "jpg" to the start of the possible_exts list, ensuring that it will be the extension suggested by fif.
[vec![String::from("jpg")], possible_exts].concat()
} else if essence == mime::TEXT_XML.essence_str() || essence == "application/xml" {
// a somewhat similar case arises with XML files - the first suggested extension is "asa", when it should
// (in my opinion) be "xml".
// there's also another problem: SVG files can easily be misidentified as XML files, because they usually
// *are* valid XML - the more whitespace and comments an SVG file begins with, the more bytes must be read
// before it's possible to determine that it's an SVG rather than an XML file. to "fix" this, we can add "svg"
// as a valid extension for XML files, ensuring that SVG files misidentified as XML will still be considered
// to have valid extensions.
// TODO: if a file is detected as application/xml, but it has an extension like "xht" which corresponds to
// "application/xhtml+xml", let it through - in other words, if it's identified as application/xml, but its
// extension is classed as application/*+xml, consider it OK
[vec![String::from("xml"), String::from("svg")], possible_exts].concat()
} else if essence == "application/msword" {
// classic office files considered harmful
vec![String::from("doc"), String::from("xls"), String::from("ppt")]
} else if essence == "application/zip" {
// neither xdg-mime nor infer seem to be able to detect office XML files properly...
[vec![String::from("zip"), String::from("docx"), String::from("xlsx"), String::from("pptx")], possible_exts].concat()
} else if essence == "application/x-ms-dos-executable" {
// both .dll and .exe files are given the same mime type... but you definitely don't want to rename one to the
// other!
[vec![String::from("dll"), String::from("exe")], possible_exts].concat()
} else {
possible_exts
})
},
None => None
}
}
}

1
src/lib.rs

@ -4,7 +4,6 @@
pub mod files;
pub mod findings;
pub mod formats;
pub mod inspectors;
pub mod mime_db;
pub mod parameters;
pub mod utils;

2
src/parameters.rs

@ -1,7 +1,7 @@
//! [Clap] struct used to parse command line arguments.
use crate::String as StringType;
use crate::utils::{clap_long_version, clap_version};
use crate::String as StringType;
use cfg_if::cfg_if;
use clap::{AppSettings, Clap};
use std::collections::BTreeSet;

11
src/tests/mod.rs

@ -1,7 +1,7 @@
use fif::files::{mime_extension_lookup, BUF_SIZE};
use fif::files::{scan_directory, scan_from_walkdir};
use fif::findings::Findings;
use fif::formats::{Format, PowerShell, Shell};
use fif::inspectors::{mime_extension_lookup, BUF_SIZE};
use fif::mime_db::MimeDb;
use fif::String;
@ -66,18 +66,19 @@ fn detect_type() {
/// Ensure that `mime_extension_lookup` works as expected, and that the set of extensions for JPEG, PNG, PDF, and ZIP
/// contain "jpg", "png", "pdf", and "zip", respectively.
fn recommend_ext() {
use std::string::String as StdString;
assert!(mime_extension_lookup(IMAGE_JPEG.essence_str().into())
.unwrap()
.contains(&String::from("jpg")));
.contains(&StdString::from("jpg")));
assert!(mime_extension_lookup(IMAGE_PNG.essence_str().into())
.unwrap()
.contains(&String::from("png")));
.contains(&StdString::from("png")));
assert!(mime_extension_lookup(APPLICATION_PDF.essence_str().into())
.unwrap()
.contains(&String::from("pdf")));
.contains(&StdString::from("pdf")));
assert!(mime_extension_lookup(application_zip().essence_str().into())
.unwrap()
.contains(&String::from("zip")));
.contains(&StdString::from("zip")));
}
#[test]

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