mirror of https://github.com/ctz/rustls
74 lines
1.9 KiB
Rust
74 lines
1.9 KiB
Rust
use alloc::boxed::Box;
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use zeroize::Zeroize;
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/// A concrete HMAC implementation, for a single cryptographic hash function.
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///
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/// You should have one object that implements this trait for HMAC-SHA256, another
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/// for HMAC-SHA384, etc.
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pub trait Hmac: Send + Sync {
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/// Prepare to use `key` as a HMAC key.
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fn with_key(&self, key: &[u8]) -> Box<dyn Key>;
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/// Give the length of the underlying hash function. In RFC2104 terminology this is `L`.
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fn hash_output_len(&self) -> usize;
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/// Return true if this is backed by a FIPS-approved implementation.
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fn fips_mode(&self) -> bool {
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false
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}
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}
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/// A HMAC tag, stored as a value.
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#[derive(Clone)]
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pub struct Tag {
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buf: [u8; Self::MAX_LEN],
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used: usize,
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}
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impl Tag {
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/// Build a tag by copying a byte slice.
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///
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/// The slice can be up to [`Tag::MAX_LEN`] bytes in length.
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pub fn new(bytes: &[u8]) -> Self {
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let mut tag = Self {
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buf: [0u8; Self::MAX_LEN],
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used: bytes.len(),
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};
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tag.buf[..bytes.len()].copy_from_slice(bytes);
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tag
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}
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/// Maximum supported HMAC tag size: supports up to SHA512.
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pub const MAX_LEN: usize = 64;
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}
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impl Drop for Tag {
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fn drop(&mut self) {
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self.buf.zeroize();
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}
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}
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impl AsRef<[u8]> for Tag {
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fn as_ref(&self) -> &[u8] {
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&self.buf[..self.used]
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}
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}
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/// A HMAC key that is ready for use.
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///
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/// The algorithm used is implicit in the `Hmac` object that produced the key.
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pub trait Key: Send + Sync {
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/// Calculates a tag over `data` -- a slice of byte slices.
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fn sign(&self, data: &[&[u8]]) -> Tag {
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self.sign_concat(&[], data, &[])
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}
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/// Calculates a tag over the concatenation of `first`, the items in `middle`, and `last`.
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fn sign_concat(&self, first: &[u8], middle: &[&[u8]], last: &[u8]) -> Tag;
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/// Returns the length of the tag returned by a computation using
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/// this key.
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fn tag_len(&self) -> usize;
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}
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