IMAP Protocol

This library provides complete and detailed parsing and construction of IMAP4rev1 commands and responses.

The three entry points are greeting (to parse the first message from a server), command (to parse any message from a client), and response (to parse any response or result from a server.) Every parser takes an input (&[u8]) and produces a remainder and a parsed value.

Features

Rust's type system is used to enforce correctness and make the library misuse-resistant. It should not be possible to construct messages that violate the IMAP specification.

Fuzzing (via cargo fuzz) and property-based tests are used to uncover parsing and serialization bugs. For example, the library is fuzz-tested to never produce a message it can not parse itself. The complete formal syntax of IMAP4rev1 is implemented.

Every parser works in streaming mode, i.e., all parsers will return Incomplete when there is not enough data to make a final decision, and no command or response will ever be truncated.

Usage

``rust use imap_codec::{ types::codec::Encode, // This trait provides theencode` method. parse::command::command, // This is the command parser. };

fn main() { let input = b"ABCD UID FETCH 1,2:* (BODY.PEEK[1.2.3.4.MIME]<42.1337>)\r\n";

let (_remainder, parsed) = command(input).unwrap();
println!("// Parsed:");
println!("{:#?}", parsed);

let mut serialized = Vec::new();
parsed.encode(&mut serialized).unwrap(); // This could be send over the network.

let serialized = String::from_utf8(serialized).unwrap(); // Not every IMAP message is valid UTF-8.
println!("// Serialized:"); // We just ignore that, so that we can print the message.
println!("// {}", serialized);

} ```

Example (binary)

Have a look at the parse_* examples and try any IMAP message, e.g.

$ cargo run --example=parse_command

Sample IMAP4rev1 connection from RFC 3501

This output was generated by reading the trace from the IMAP RFC section 8, printing the input (first line), printing the Debug of the object (second line), and serializing it again (third line).

```rust // * OK IMAP4rev1 Service Ready Status(Ok { tag: None, code: None, text: Text("IMAP4rev1 Service Ready") }) // * OK IMAP4rev1 Service Ready

// a001 login mrc secret Command { tag: Tag("a001"), body: Login { username: Atom(Atom("mrc")), password: Atom(Atom("secret")) } } // a001 LOGIN mrc secret

// a001 OK LOGIN completed Status(Ok { tag: Some(Tag("a001")), code: None, text: Text("LOGIN completed") }) // a001 OK LOGIN completed

// a002 select inbox Command { tag: Tag("a002"), body: Select { mailbox: Inbox } } // a002 SELECT INBOX

// * 18 EXISTS Data(Exists(18)) // * 18 EXISTS

// * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) Data(Flags([Answered, Flagged, Deleted, Seen, Draft])) // * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)

// * 2 RECENT Data(Recent(2)) // * 2 RECENT

// * OK [UNSEEN 17] Message 17 is the first unseen message Status(Ok { tag: None, code: Some(Unseen(17)), text: Text("Message 17 is the first unseen message") }) // * OK [UNSEEN 17] Message 17 is the first unseen message

// * OK [UIDVALIDITY 3857529045] UIDs valid Status(Ok { tag: None, code: Some(UidValidity(3857529045)), text: Text("UIDs valid") }) // * OK [UIDVALIDITY 3857529045] UIDs valid

// a002 OK [READ-WRITE] SELECT completed Status(Ok { tag: Some(Tag("a002")), code: Some(ReadWrite), text: Text("SELECT completed") }) // a002 OK [READ-WRITE] SELECT completed

// a003 fetch 12 full Command { tag: Tag("a003"), body: Fetch { sequence_set: SequenceSet([Single(Value(12))]), attributes: Macro(Full), uid: false } } // a003 FETCH 12 FULL

// * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700" RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)" "IMAP4rev1 WG mtg summary and minutes" (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) ((NIL NIL "imap" "cac.washington.edu")) ((NIL NIL "minutes" "CNRI.Reston.VA.US")("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL "B27397-0100000@cac.washington.edu") BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 92)) Data(Fetch { seqoruid: 12, attributes: [Flags([Seen]), InternalDate(1996-07-17T02:44:25-07:00), Rfc822Size(4286), Envelope(Envelope { date: NString(Some(Quoted(Quoted("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)")))), subject: NString(Some(Quoted(Quoted("IMAP4rev1 WG mtg summary and minutes")))), from: [Address { name: NString(Some(Quoted(Quoted("Terry Gray")))), adl: NString(None), mailbox: NString(Some(Quoted(Quoted("gray")))), host: NString(Some(Quoted(Quoted("cac.washington.edu")))) }], sender: [Address { name: NString(Some(Quoted(Quoted("Terry Gray")))), adl: NString(None), mailbox: NString(Some(Quoted(Quoted("gray")))), host: NString(Some(Quoted(Quoted("cac.washington.edu")))) }], replyto: [Address { name: NString(Some(Quoted(Quoted("Terry Gray")))), adl: NString(None), mailbox: NString(Some(Quoted(Quoted("gray")))), host: NString(Some(Quoted(Quoted("cac.washington.edu")))) }], to: [Address { name: NString(None), adl: NString(None), mailbox: NString(Some(Quoted(Quoted("imap")))), host: NString(Some(Quoted(Quoted("cac.washington.edu")))) }], cc: [Address { name: NString(None), adl: NString(None), mailbox: NString(Some(Quoted(Quoted("minutes")))), host: NString(Some(Quoted(Quoted("CNRI.Reston.VA.US")))) }, Address { name: NString(Some(Quoted(Quoted("John Klensin")))), adl: NString(None), mailbox: NString(Some(Quoted(Quoted("KLENSIN")))), host: NString(Some(Quoted(Quoted("MIT.EDU")))) }], bcc: [], inreplyto: NString(None), messageid: NString(Some(Quoted(Quoted("B27397-0100000@cac.washington.edu")))) }), Body(Single { body: Body { basic: BasicFields { parameterlist: [(Quoted(Quoted("CHARSET")), Quoted(Quoted("US-ASCII")))], id: NString(None), description: NString(None), contenttransferencoding: Quoted(Quoted("7BIT")), size: 3028 }, specific: Text { subtype: Quoted(Quoted("PLAIN")), numberof_lines: 92 } }, extension: None })] }) // * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700" RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)" "IMAP4rev1 WG mtg summary and minutes" (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) ((NIL NIL "imap" "cac.washington.edu")) ((NIL NIL "minutes" "CNRI.Reston.VA.US")("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL "B27397-0100000@cac.washington.edu") BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 92))

// a003 OK FETCH completed Status(Ok { tag: Some(Tag("a003")), code: None, text: Text("FETCH completed") }) // a003 OK FETCH completed

// a004 fetch 12 body[header] Command { tag: Tag("a004"), body: Fetch { sequence_set: SequenceSet([Single(Value(12))]), attributes: FetchAttributes([BodyExt { section: Some(Header(None)), partial: None, peek: false }]), uid: false } } // a004 FETCH 12 BODY[HEADER]

// a004 OK FETCH completed Status(Ok { tag: Some(Tag("a004")), code: None, text: Text("FETCH completed") }) // a004 OK FETCH completed

// a005 store 12 +flags \deleted Command { tag: Tag("a005"), body: Store { sequence_set: SequenceSet([Single(Value(12))]), kind: Add, response: Answer, flags: [Deleted], uid: false } } // a005 STORE 12 +FLAGS (\Deleted)

// * 12 FETCH (FLAGS (\Seen \Deleted)) Data(Fetch { seqoruid: 12, attributes: [Flags([Seen, Deleted])] }) // * 12 FETCH (FLAGS (\Seen \Deleted))

// a005 OK +FLAGS completed Status(Ok { tag: Some(Tag("a005")), code: None, text: Text("+FLAGS completed") }) // a005 OK +FLAGS completed

// a006 logout Command { tag: Tag("a006"), body: Logout } // a006 LOGOUT

// * BYE IMAP4rev1 server terminating connection Status(Bye { code: None, text: Text("IMAP4rev1 server terminating connection") }) // * BYE IMAP4rev1 server terminating connection

// a006 OK LOGOUT completed Status(Ok { tag: Some(Tag("a006")), code: None, text: Text("LOGOUT completed") }) // a006 OK LOGOUT completed ```

A Note on Types

Due to the correctness guarantees (and the mentioned allocation strategy), the library uses multiple "string types" like Atom, Tag, NString, and IString.

A Note on IMAP literals

IMAP literals make separating the parsing logic from the application logic difficult. When a parser recognizes a literal (e.g. "{42}"), which can be used anywhere, a so-called continuation response ("+ ...") must be sent. Otherwise, the client or server will not send any more data, and a parser would always return Incomplete(42).

A possible solution is to implement a "framing codec" first. This strategy is motivated by the IMAP RFC:

The protocol receiver of an IMAP4rev1 client or server is either reading a line, or is reading a sequence of octets with a known count followed by a line.

Thus, the framing codec may be implemented like this...

loop { line = read_line() if line.has_literal() { literal = read_literal(amount) } }

A variant of this procedure is provided in examples/parse_command.rs.

License

This crate is dual-licensed under Apache 2.0 and MIT terms.