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| </pre><pre class="rust"><code><span class="comment">// Copyright 2016 Brian Smith. |
| // |
| // Permission to use, copy, modify, and/or distribute this software for any |
| // purpose with or without fee is hereby granted, provided that the above |
| // copyright notice and this permission notice appear in all copies. |
| // |
| // THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES |
| // WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| // MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY |
| // SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| // WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION |
| // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN |
| // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
| |
| </span><span class="doccomment">//! The [chacha20-poly1305@openssh.com] AEAD-ish construct. |
| //! |
| //! This should only be used by SSH implementations. It has a similar, but |
| //! different API from `ring::aead` because the construct cannot use the same |
| //! API as `ring::aead` due to the way the construct handles the encrypted |
| //! packet length. |
| //! |
| //! The concatenation of a and b is denoted `a||b`. `K_1` and `K_2` are defined |
| //! in the [chacha20-poly1305@openssh.com] specification. `packet_length`, |
| //! `padding_length`, `payload`, and `random padding` are defined in |
| //! [RFC 4253]. The term `plaintext` is used as a shorthand for |
| //! `padding_length||payload||random padding`. |
| //! |
| //! [chacha20-poly1305@openssh.com]: |
| //! http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.chacha20poly1305?annotate=HEAD |
| //! [RFC 4253]: https://tools.ietf.org/html/rfc4253 |
| |
| </span><span class="kw">use super</span>::{ |
| chacha::{<span class="self">self</span>, <span class="kw-2">*</span>}, |
| chacha20_poly1305::derive_poly1305_key, |
| cpu, poly1305, Nonce, Tag, |
| }; |
| <span class="kw">use crate</span>::{constant_time, endian::<span class="kw-2">*</span>, error}; |
| <span class="kw">use </span>core::convert::TryInto; |
| |
| <span class="doccomment">/// A key for sealing packets. |
| </span><span class="kw">pub struct </span>SealingKey { |
| key: Key, |
| } |
| |
| <span class="kw">impl </span>SealingKey { |
| <span class="doccomment">/// Constructs a new `SealingKey`. |
| </span><span class="kw">pub fn </span>new(key_material: <span class="kw-2">&</span>[u8; KEY_LEN]) -> SealingKey { |
| SealingKey { |
| key: Key::new(key_material, cpu::features()), |
| } |
| } |
| |
| <span class="doccomment">/// Seals (encrypts and signs) a packet. |
| /// |
| /// On input, `plaintext_in_ciphertext_out` must contain the unencrypted |
| /// `packet_length||plaintext` where `plaintext` is the |
| /// `padding_length||payload||random padding`. It will be overwritten by |
| /// `encrypted_packet_length||ciphertext`, where `encrypted_packet_length` |
| /// is encrypted with `K_1` and `ciphertext` is encrypted by `K_2`. |
| </span><span class="kw">pub fn </span>seal_in_place( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| sequence_number: u32, |
| plaintext_in_ciphertext_out: <span class="kw-2">&mut </span>[u8], |
| tag_out: <span class="kw-2">&mut </span>[u8; TAG_LEN], |
| ) { |
| <span class="kw">let </span><span class="kw-2">mut </span>counter = make_counter(sequence_number); |
| <span class="kw">let </span>poly_key = |
| derive_poly1305_key(<span class="kw-2">&</span><span class="self">self</span>.key.k_2, counter.increment(), <span class="self">self</span>.key.cpu_features); |
| |
| { |
| <span class="kw">let </span>(len_in_out, data_and_padding_in_out) = |
| plaintext_in_ciphertext_out.split_at_mut(PACKET_LENGTH_LEN); |
| |
| <span class="self">self</span>.key |
| .k_1 |
| .encrypt_in_place(make_counter(sequence_number), len_in_out); |
| <span class="self">self</span>.key |
| .k_2 |
| .encrypt_in_place(counter, data_and_padding_in_out); |
| } |
| |
| <span class="kw">let </span>Tag(tag) = poly1305::sign(poly_key, plaintext_in_ciphertext_out); |
| tag_out.copy_from_slice(tag.as_ref()); |
| } |
| } |
| |
| <span class="doccomment">/// A key for opening packets. |
| </span><span class="kw">pub struct </span>OpeningKey { |
| key: Key, |
| } |
| |
| <span class="kw">impl </span>OpeningKey { |
| <span class="doccomment">/// Constructs a new `OpeningKey`. |
| </span><span class="kw">pub fn </span>new(key_material: <span class="kw-2">&</span>[u8; KEY_LEN]) -> OpeningKey { |
| OpeningKey { |
| key: Key::new(key_material, cpu::features()), |
| } |
| } |
| |
| <span class="doccomment">/// Returns the decrypted, but unauthenticated, packet length. |
| /// |
| /// Importantly, the result won't be authenticated until `open_in_place` is |
| /// called. |
| </span><span class="kw">pub fn </span>decrypt_packet_length( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| sequence_number: u32, |
| encrypted_packet_length: [u8; PACKET_LENGTH_LEN], |
| ) -> [u8; PACKET_LENGTH_LEN] { |
| <span class="kw">let </span><span class="kw-2">mut </span>packet_length = encrypted_packet_length; |
| <span class="kw">let </span>counter = make_counter(sequence_number); |
| <span class="self">self</span>.key.k_1.encrypt_in_place(counter, <span class="kw-2">&mut </span>packet_length); |
| packet_length |
| } |
| |
| <span class="doccomment">/// Opens (authenticates and decrypts) a packet. |
| /// |
| /// `ciphertext_in_plaintext_out` must be of the form |
| /// `encrypted_packet_length||ciphertext` where `ciphertext` is the |
| /// encrypted `plaintext`. When the function succeeds the ciphertext is |
| /// replaced by the plaintext and the result is `Ok(plaintext)`, where |
| /// `plaintext` is `&ciphertext_in_plaintext_out[PACKET_LENGTH_LEN..]`; |
| /// otherwise the contents of `ciphertext_in_plaintext_out` are unspecified |
| /// and must not be used. |
| </span><span class="kw">pub fn </span>open_in_place<<span class="lifetime">'a</span>>( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| sequence_number: u32, |
| ciphertext_in_plaintext_out: <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>[u8], |
| tag: <span class="kw-2">&</span>[u8; TAG_LEN], |
| ) -> <span class="prelude-ty">Result</span><<span class="kw-2">&</span><span class="lifetime">'a </span>[u8], error::Unspecified> { |
| <span class="kw">let </span><span class="kw-2">mut </span>counter = make_counter(sequence_number); |
| |
| <span class="comment">// We must verify the tag before decrypting so that |
| // `ciphertext_in_plaintext_out` is unmodified if verification fails. |
| // This is beyond what we guarantee. |
| </span><span class="kw">let </span>poly_key = |
| derive_poly1305_key(<span class="kw-2">&</span><span class="self">self</span>.key.k_2, counter.increment(), <span class="self">self</span>.key.cpu_features); |
| verify(poly_key, ciphertext_in_plaintext_out, tag)<span class="question-mark">?</span>; |
| |
| <span class="kw">let </span>plaintext_in_ciphertext_out = <span class="kw-2">&mut </span>ciphertext_in_plaintext_out[PACKET_LENGTH_LEN..]; |
| <span class="self">self</span>.key |
| .k_2 |
| .encrypt_in_place(counter, plaintext_in_ciphertext_out); |
| |
| <span class="prelude-val">Ok</span>(plaintext_in_ciphertext_out) |
| } |
| } |
| |
| <span class="kw">struct </span>Key { |
| k_1: chacha::Key, |
| k_2: chacha::Key, |
| cpu_features: cpu::Features, |
| } |
| |
| <span class="kw">impl </span>Key { |
| <span class="kw">fn </span>new(key_material: <span class="kw-2">&</span>[u8; KEY_LEN], cpu_features: cpu::Features) -> Key { |
| <span class="comment">// The first half becomes K_2 and the second half becomes K_1. |
| </span><span class="kw">let </span>(k_2, k_1) = key_material.split_at(chacha::KEY_LEN); |
| <span class="kw">let </span>k_1: [u8; chacha::KEY_LEN] = k_1.try_into().unwrap(); |
| <span class="kw">let </span>k_2: [u8; chacha::KEY_LEN] = k_2.try_into().unwrap(); |
| Key { |
| k_1: chacha::Key::from(k_1), |
| k_2: chacha::Key::from(k_2), |
| cpu_features, |
| } |
| } |
| } |
| |
| <span class="kw">fn </span>make_counter(sequence_number: u32) -> Counter { |
| <span class="kw">let </span>nonce = [ |
| BigEndian::ZERO, |
| BigEndian::ZERO, |
| BigEndian::from(sequence_number), |
| ]; |
| Counter::zero(Nonce::assume_unique_for_key(<span class="kw-2">*</span>(nonce.as_byte_array()))) |
| } |
| |
| <span class="doccomment">/// The length of key. |
| </span><span class="kw">pub const </span>KEY_LEN: usize = chacha::KEY_LEN * <span class="number">2</span>; |
| |
| <span class="doccomment">/// The length in bytes of the `packet_length` field in a SSH packet. |
| </span><span class="kw">pub const </span>PACKET_LENGTH_LEN: usize = <span class="number">4</span>; <span class="comment">// 32 bits |
| |
| </span><span class="doccomment">/// The length in bytes of an authentication tag. |
| </span><span class="kw">pub const </span>TAG_LEN: usize = <span class="kw">super</span>::BLOCK_LEN; |
| |
| <span class="kw">fn </span>verify(key: poly1305::Key, msg: <span class="kw-2">&</span>[u8], tag: <span class="kw-2">&</span>[u8; TAG_LEN]) -> <span class="prelude-ty">Result</span><(), error::Unspecified> { |
| <span class="kw">let </span>Tag(calculated_tag) = poly1305::sign(key, msg); |
| constant_time::verify_slices_are_equal(calculated_tag.as_ref(), tag) |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="ring" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
