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// Copyright 2019 Alexandros Frantzis // // This Source Code Form is subject to the terms of the Mozilla Public // License, v. 2.0. If a copy of the MPL was not distributed with this // file, You can obtain one at https://mozilla.org/MPL/2.0/. // // SPDX-License-Identifier: MPL-2.0 //! The mda crate provides a library for writing custom Mail Deliver Agents. It //! supports local delivery to maildirs, access to normalized email byte //! data for easier processing, and access to individual header fields. //! //! Email data normalization involves ensuring header fields are in single //! lines, decoding text parts of the message that use some kind of transfer //! encoding (e.g., base64), and converting all text to UTF-8. The original //! (non-normalized) email data is used during delivery. //! //! This crate also exposes convenience methods for regular expression searching //! and processing/filtering of emails. //! //! # Email construction //! //! The [Email struct](struct.Email.html) is the basic abstraction of the `mda` //! crate. To construct an Email use the //! [Email::from_stdin](struct.Email.html#method.from_stdin) or //! [Email::from_vec](struct.Email.html#method.from_vec) method. //! //! ```no_run //! use mda::Email; //! let email = Email::from_stdin()?; //! let email = Email::from_vec(vec![97, 98, 99])?; //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` //! //! # Email delivery //! //! Use the //! [Email::deliver_to_maildir](struct.Email.html#method.deliver_to_maildir) //! method to deliver the email to local maildir directories. Note that //! the original (non-normalized) email data is used during delivery. //! //! ```no_run //! use mda::Email; //! let email = Email::from_stdin()?; //! email.deliver_to_maildir("/my/maildir/path")?; //! email.deliver_to_maildir("/my/other/maildir/path")?; //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` //! //! # Accessing email header fields //! //! Use the [Email::header_field](struct.Email.html#method.header_field) and //! [Email::header_field_all_occurrences](struct.Email.html#method.header_field_all_occurrences) //! methods to access the email header fields. Any MIME encoded words in the //! header field values are decoded and the field value is converted to UTF-8. //! //! ```no_run //! use mda::Email; //! let email = Email::from_stdin()?; //! let to = email.header_field("To").unwrap_or(""); //! if to.contains("me@example.com") { //! email.deliver_to_maildir("/my/maildir/path")?; //! } //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` //! //! # Searching with regular expressions //! //! The [EmailRegex](trait.EmailRegex.html) trait provides convenience methods //! for searching the header, the body or the whole email with regular //! expressions. The convenience functions use case-insensitive, multi-line //! search (`^` and `$` match beginning and end of lines). If the above don't //! match your needs, or you require additional functionality, you can perform //! manual regex search using the email data. //! //! ```no_run //! use mda::{Email, EmailRegex}; //! let email = Email::from_stdin()?; //! if email.header().search(r"^To:.*me@example.com")? { //! email.deliver_to_maildir("/my/maildir/path")?; //! } //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` //! //! # Processing and filtering the email with external programs //! //! Use the [Email::filter](struct.Email.html#method.filter) and //! [Email::from_stdin_filtered](struct.Email.html#method.from_stdin_filtered) //! methods to filter the email, in both cases creating a new email. //! //! ```no_run //! use mda::Email; //! // Filtering directly from stdin is more efficient. //! let email = Email::from_stdin_filtered(&["bogofilter", "-ep"])?; //! let bogosity = email.header_field("X-Bogosity").unwrap_or(""); //! if bogosity.contains("Spam, tests=bogofilter") { //! email.deliver_to_maildir("/my/spam/path")?; //! } //! // We can also filter at any other time. //! let email = email.filter(&["bogofilter", "-ep"])?; //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` //! //! To perform more general processing use the //! [Email::process](struct.Email.html#method.process) //! method: //! //! ```no_run //! use mda::Email; //! let email = Email::from_stdin()?; //! let output = email.process(&["bogofilter"])?; //! if let Some(0) = output.status.code() { //! email.deliver_to_maildir("/my/spam/path")?; //! } //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` //! //! # Access to byte data //! //! Use the [Email::header](struct.Email.html#method.header), //! [Email::body](struct.Email.html#method.body), //! [Email::data](struct.Email.html#method.data) methods to access the //! normalized byte data of the header, body and whole email respectively. //! //! Normalization involves ensuring header fields are in single lines, decoding //! text parts of the message that use some kind of transfer encoding (e.g., //! base64), and converting all text to UTF-8 character encoding. //! //! If for some reason you need access to non-normalized data use //! [Email::raw_data](struct.Email.html#method.raw_data). //! //! ```no_run //! use std::str; //! use mda::Email; //! let email = Email::from_stdin()?; //! let body_str = String::from_utf8_lossy(email.header()); //! //! if body_str.contains("FREE BEER") { //! email.deliver_to_maildir("/my/spam/path")?; //! } //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` //! //! # Decide delivery durability vs speed trade-off //! //! Use the [Email::set_delivery_durability](struct.Email.html#method.set_delivery_durability) //! to decide which [DeliveryDurability](enum.DeliveryDurability.html) method to use. //! By default the most durable (but also slower) method is used. //! //! ```no_run //! use mda::{Email, DeliveryDurability}; //! let mut email = Email::from_stdin()?; //! email.set_delivery_durability(DeliveryDurability::FileSyncOnly); //! # Ok::<(), Box<dyn std::error::Error>>(()) //! ``` mod deliver; mod regex; mod processing; mod normalize; mod decode; use std::io; use std::io::prelude::*; use std::path::{PathBuf, Path}; use std::sync:: {Arc, Mutex, RwLock}; use std::collections::HashMap; use deliver::{Maildir, EmailFilenameGenerator}; use normalize::normalize_email; pub use crate::regex::EmailRegex; pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>; fn find_empty_line(data: &[u8]) -> Option<usize> { data.windows(2).position(|w| w[0]== b'\n' && (w[1] == b'\n' || w[1] == b'\r')) } /// The method to use to try to guarantee durable email delivery. #[derive(PartialEq, Copy, Clone)] pub enum DeliveryDurability { /// Perform both file and directory syncing during delivery. /// This is the default delivery durability method. FileAndDirSync, /// Perform only file sync during delivery. This method is /// potentially much faster, and is used by many existing /// MDAs, but, depending on the used filesystem, may not /// provide the required delivery durability guarantees. FileSyncOnly, } /// A representation of an email. pub struct Email { data: Vec<u8>, normalized_data: Vec<u8>, body_index: usize, deliver_path: RwLock<Option<PathBuf>>, fields: HashMap<String, Vec<String>>, email_filename_gen: Arc<Mutex<EmailFilenameGenerator>>, delivery_durability: DeliveryDurability, } impl Email { /// Creates an `Email` by reading data from stdin. /// /// # Example /// /// ```no_run /// # use mda::Email; /// let email = Email::from_stdin()?; /// # Ok::<(), Box<dyn std::error::Error>>(()) /// ``` pub fn from_stdin() -> Result<Self> { let stdin = io::stdin(); let mut data = Vec::new(); stdin.lock().read_to_end(&mut data)?; Email::from_vec(data) } /// Creates an `Email` by using data passed in a `Vec<u8>`. /// /// # Example /// /// ```no_run /// # use mda::Email; /// let email = Email::from_vec(vec![1, 2, 3])?; /// # Ok::<(), Box<dyn std::error::Error>>(()) /// ``` pub fn from_vec(data: Vec<u8>) -> Result<Self> { let (normalized_data, fields) = normalize_email(&data); let body_index = find_empty_line(&normalized_data).unwrap_or(normalized_data.len()); let email_filename_gen = Arc::new(Mutex::new(EmailFilenameGenerator::new())); Ok( Email{ data: data, normalized_data: normalized_data, body_index: body_index, deliver_path: RwLock::new(None), fields: fields, email_filename_gen: email_filename_gen, delivery_durability: DeliveryDurability::FileAndDirSync, } ) } /// Sets the durability method for delivery of this email. /// /// # Example /// /// ```no_run /// # use mda::{DeliveryDurability, Email}; /// let mut email = Email::from_stdin()?; /// email.set_delivery_durability(DeliveryDurability::FileSyncOnly); /// # Ok::<(), Box<dyn std::error::Error>>(()) /// ``` pub fn set_delivery_durability(&mut self, delivery_durability: DeliveryDurability) { self.delivery_durability = delivery_durability; } /// Returns the value of a header field, if present. If a field occurs /// multiple times, the value of the first occurrence is returned. /// /// # Example /// /// ```no_run /// # use mda::Email; /// let email = Email::from_stdin()?; /// let to = email.header_field("To").unwrap_or(""); /// # Ok::<(), Box<dyn std::error::Error>>(()) /// ``` pub fn header_field(&self, name: &str) -> Option<&str> { self.fields.get(&name.to_lowercase()).map(|v| v[0].as_str()) } /// Returns the values from all occurrences of a header field, if present. /// /// # Example /// /// ```no_run /// # use mda::Email; /// let email = Email::from_stdin()?; /// if let Some(all_received) = email.header_field_all_occurrences("Received") { /// // process all_received /// } /// # Ok::<(), Box<dyn std::error::Error>>(()) /// ``` pub fn header_field_all_occurrences(&self, name: &str) -> Option<&Vec<String>> { self.fields.get(&name.to_lowercase()).map(|v| v) } /// Delivers the email to the specified maildir. If the maildir isn't /// present it is created. /// /// The first delivery of an email involves writing the email data to /// the target file, whereas subsequent deliveries try to use a hard link /// to the first delivery, falling back to a normal write if needed. /// /// The email is delivered durably by syncing both the file and the /// associated directories (`DeliveryDurability::FileAndDirSync`), /// unless a different durability method is specified with /// `set_delivery_durability`. /// /// # Example /// /// ```no_run /// # use mda::Email; /// let email = Email::from_stdin()?; /// email.deliver_to_maildir("/path/to/maildir/")?; /// # Ok::<(), Box<dyn std::error::Error>>(()) /// ``` pub fn deliver_to_maildir(&self, path: impl AsRef<Path>) -> Result<PathBuf> { self.deliver_to_maildir_path(path.as_ref()) } fn deliver_to_maildir_path(&self, path: &Path) -> Result<PathBuf> { let maildir = Maildir::open_or_create(&path, self.email_filename_gen.clone())?; if let Some(deliver_path) = self.deliver_path.read().unwrap().as_ref() { let email_path_result = maildir.deliver_with_hard_link( deliver_path, self.delivery_durability); if email_path_result.is_ok() { return email_path_result; } } let email_path = maildir.deliver(&self.data, self.delivery_durability)?; *self.deliver_path.write().unwrap() = Some(email_path.clone()); Ok(email_path) } /// Returns whether the email has been delivered to at least one maildir. /// /// # Example /// /// ```no_run /// # use mda::Email; /// let email = Email::from_stdin()?; /// if !email.has_been_delivered() { /// email.deliver_to_maildir("/fallback/maildir/")?; /// } /// # Ok::<(), Box<dyn std::error::Error>>(()) /// ``` pub fn has_been_delivered(&self) -> bool { self.deliver_path.read().unwrap().is_some() } /// Provides access to the normalized email byte data. pub fn data(&self) -> &[u8] { &self.normalized_data } /// Provides access to the normalized email header byte data. pub fn header(&self) -> &[u8] { &self.normalized_data[..self.body_index] } /// Provides access to the normalized email body byte data. pub fn body(&self) -> &[u8] { &self.normalized_data[self.body_index..] } /// Provides access to the raw (non-normalized) email byte data. pub fn raw_data(&self) -> &[u8] { &self.data } }