portable_rustls/crypto/
hmac.rs

1use alloc::boxed::Box;
2
3use zeroize::Zeroize;
4
5/// A concrete HMAC implementation, for a single cryptographic hash function.
6///
7/// You should have one object that implements this trait for HMAC-SHA256, another
8/// for HMAC-SHA384, etc.
9pub trait Hmac: Send + Sync {
10    /// Prepare to use `key` as a HMAC key.
11    fn with_key(&self, key: &[u8]) -> Box<dyn Key>;
12
13    /// Give the length of the underlying hash function.  In RFC2104 terminology this is `L`.
14    fn hash_output_len(&self) -> usize;
15
16    /// Return `true` if this is backed by a FIPS-approved implementation.
17    #[cfg(unstable_api_not_supported)] // [FIPS REMOVED FROM THIS FORK]
18    fn fips(&self) -> bool {
19        false
20    }
21}
22
23/// A HMAC tag, stored as a value.
24#[derive(Clone)]
25pub struct Tag {
26    buf: [u8; Self::MAX_LEN],
27    used: usize,
28}
29
30impl Tag {
31    /// Build a tag by copying a byte slice.
32    ///
33    /// The slice can be up to [`Tag::MAX_LEN`] bytes in length.
34    pub fn new(bytes: &[u8]) -> Self {
35        let mut tag = Self {
36            buf: [0u8; Self::MAX_LEN],
37            used: bytes.len(),
38        };
39        tag.buf[..bytes.len()].copy_from_slice(bytes);
40        tag
41    }
42
43    /// Maximum supported HMAC tag size: supports up to SHA512.
44    pub const MAX_LEN: usize = 64;
45}
46
47impl Drop for Tag {
48    fn drop(&mut self) {
49        self.buf.zeroize();
50    }
51}
52
53impl AsRef<[u8]> for Tag {
54    fn as_ref(&self) -> &[u8] {
55        &self.buf[..self.used]
56    }
57}
58
59/// A HMAC key that is ready for use.
60///
61/// The algorithm used is implicit in the `Hmac` object that produced the key.
62pub trait Key: Send + Sync {
63    /// Calculates a tag over `data` -- a slice of byte slices.
64    fn sign(&self, data: &[&[u8]]) -> Tag {
65        self.sign_concat(&[], data, &[])
66    }
67
68    /// Calculates a tag over the concatenation of `first`, the items in `middle`, and `last`.
69    fn sign_concat(&self, first: &[u8], middle: &[&[u8]], last: &[u8]) -> Tag;
70
71    /// Returns the length of the tag returned by a computation using
72    /// this key.
73    fn tag_len(&self) -> usize;
74}
portable_rustls/crypto/hmac.rs

portable_rustls/crypto/
hmac.rs
