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|
//! Cipher Type Byte.
//!
//! See [Section 4.2 of RFC 4880] for more details.
//!
//! [Section 4.2 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-4.2
use std::ops::Deref;
use crate::{
packet::Tag,
Error,
Result
};
use crate::packet::BodyLength;
/// OpenPGP defines two packet formats: the old and the new format.
/// They both include the packet's so-called tag.
///
/// See [Section 4.2 of RFC 4880] for more details.
///
/// [Section 4.2 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-4.2
#[derive(Clone, Debug)]
pub struct CTBCommon {
/// RFC4880 Packet tag
pub tag: Tag,
}
/// The new CTB format.
///
/// See [Section 4.2 of RFC 4880] for more details.
///
/// [Section 4.2 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-4.2
#[derive(Clone, Debug)]
pub struct CTBNew {
/// Packet CTB fields
pub common: CTBCommon,
}
impl CTBNew {
/// Constructs a new-style CTB.
pub fn new(tag: Tag) -> Self {
CTBNew {
common: CTBCommon {
tag: tag,
},
}
}
}
// Allow transparent access of common fields.
impl Deref for CTBNew {
type Target = CTBCommon;
fn deref(&self) -> &Self::Target {
&self.common
}
}
/// The PacketLengthType is used as part of the [old CTB], and is
/// partially used to determine the packet's size.
///
/// See [Section 4.2.1 of RFC 4880] for more details.
///
/// [Section 4.2.1 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-4.2.1
/// [old CTB]: ./CTBOld.t.html
#[derive(Debug)]
#[derive(Clone, Copy, PartialEq)]
pub enum PacketLengthType {
/// A one-octet Body Length header encodes a length of 0 to 191 octets.
OneOctet,
/// A two-octet Body Length header encodes a length of 192 to 8383 octets.
TwoOctets,
/// A five-octet Body Length header consists of a single octet holding
/// the value 255, followed by a four-octet scalar.
FourOctets,
/// A Partial Body Length header is one octet long and encodes the length
/// of only part of the data packet.
Indeterminate,
}
// XXX: TryFrom is nightly only.
impl /* TryFrom<u8> for */ PacketLengthType {
/* type Error = failure::Error; */
/// Mirrors the nightly only TryFrom trait.
pub fn try_from(u: u8) -> Result<Self> {
match u {
0 => Ok(PacketLengthType::OneOctet),
1 => Ok(PacketLengthType::TwoOctets),
2 => Ok(PacketLengthType::FourOctets),
3 => Ok(PacketLengthType::Indeterminate),
_ => Err(Error::InvalidArgument(
format!("Invalid packet length: {}", u)).into()),
}
}
}
impl From<PacketLengthType> for u8 {
fn from(l: PacketLengthType) -> Self {
match l {
PacketLengthType::OneOctet => 0,
PacketLengthType::TwoOctets => 1,
PacketLengthType::FourOctets => 2,
PacketLengthType::Indeterminate => 3,
}
}
}
/// The old CTB format.
///
/// See [Section 4.2 of RFC 4880] for more details.
///
/// [Section 4.2 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-4.2
#[derive(Clone, Debug)]
pub struct CTBOld {
/// Common CTB fields.
pub common: CTBCommon,
/// Type of length sepcifier.
pub length_type: PacketLengthType,
}
impl CTBOld {
/// Constructs a old-style CTB.
///
/// # Errors
///
/// Returns [`Error::InvalidArgument`] if the tag or body length
/// cannot be expressed using an old-style CTB.
///
/// [`Error::InvalidArgument`]: ../../enum.Error.html#variant.InvalidArgument
pub fn new(tag: Tag, length: BodyLength) -> Result<Self> {
let n: u8 = tag.into();
// Only tags 0-15 are supported.
if n > 15 {
return Err(Error::InvalidArgument(
format!("Only tags 0-15 are supported, got: {:?} ({})",
tag, n)).into());
}
let length_type = match length {
// Assume an optimal encoding.
BodyLength::Full(l) => {
match l {
// One octet length.
0 ... 0xFF => PacketLengthType::OneOctet,
// Two octet length.
0x1_00 ... 0xFF_FF => PacketLengthType::TwoOctets,
// Four octet length,
_ => PacketLengthType::FourOctets,
}
},
BodyLength::Partial(_) =>
return Err(Error::InvalidArgument(
"Partial body lengths are not support for old format packets".
into()).into()),
BodyLength::Indeterminate =>
PacketLengthType::Indeterminate,
};
Ok(CTBOld {
common: CTBCommon {
tag: tag,
},
length_type: length_type,
})
}
}
// Allow transparent access of common fields.
impl Deref for CTBOld {
type Target = CTBCommon;
fn deref(&self) -> &Self::Target {
&self.common
}
}
/// A sum type for the different CTB variants.
///
/// There are two CTB variants: the [old CTB format] and the [new CTB
/// format].
///
/// [old CTB format]: ./CTBOld.t.html
/// [new CTB format]: ./CTBNew.t.html
///
/// Note: CTB stands for Cipher Type Byte.
#[derive(Clone, Debug)]
pub enum CTB {
/// New (current) packet header format.
New(CTBNew),
/// Old PGP 2.6 header format.
Old(CTBOld),
}
impl CTB {
/// Constructs a new-style CTB.
pub fn new(tag: Tag) -> Self {
CTB::New(CTBNew::new(tag))
}
}
// Allow transparent access of common fields.
impl Deref for CTB {
type Target = CTBCommon;
fn deref(&self) -> &Self::Target {
match self {
&CTB::New(ref ctb) => return &ctb.common,
&CTB::Old(ref ctb) => return &ctb.common,
}
}
}
impl CTB {
/// Parses a CTB as described in [Section 4.2 of RFC 4880]. This
/// function parses both new and old format CTBs.
///
/// [Section 4.2 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-4.2
pub fn from_ptag(ptag: u8) -> Result<CTB> {
// The top bit of the ptag must be set.
if ptag & 0b1000_0000 == 0 {
// XXX: Use a proper error.
return Err(
Error::MalformedPacket(
format!("Malformed CTB: MSB of ptag ({:#010b}) not set{}.",
ptag,
if ptag == '-' as u8 {
" (ptag is a dash, perhaps this is an \
ASCII-armor encoded message)"
} else {
""
})).into());
}
let new_format = ptag & 0b0100_0000 != 0;
let ctb = if new_format {
let tag = ptag & 0b0011_1111;
CTB::New(CTBNew {
common: CTBCommon {
tag: tag.into()
}})
} else {
let tag = (ptag & 0b0011_1100) >> 2;
let length_type = ptag & 0b0000_0011;
CTB::Old(CTBOld {
common: CTBCommon {
tag: tag.into(),
},
length_type: PacketLengthType::try_from(length_type)?,
})
};
Ok(ctb)
}
}
#[test]
fn ctb() {
// 0x99 = public key packet
if let CTB::Old(ctb) = CTB::from_ptag(0x99).unwrap() {
assert_eq!(ctb.tag, Tag::PublicKey);
assert_eq!(ctb.length_type, PacketLengthType::TwoOctets);
} else {
panic!("Expected an old format packet.");
}
// 0xa3 = old compressed packet
if let CTB::Old(ctb) = CTB::from_ptag(0xa3).unwrap() {
assert_eq!(ctb.tag, Tag::CompressedData);
assert_eq!(ctb.length_type,
|