1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134

#![cfg_attr(docsrs, doc(cfg(feature = "verify")))]

//! Common functions to verify a signed file

#[cfg(feature = "verify-tar")]
mod tar;
#[cfg(feature = "verify-zip")]
mod zip;

use std::io::Read;

#[cfg(feature = "verify-tar")]
pub use self::tar::{verify_tar, VerifyTarError};
#[cfg(feature = "verify-zip")]
pub use self::zip::{verify_zip, VerifyZipError};
use crate::{
    Sha512, Signature, SignatureCountLeInt, SignatureError, VerifyingKey, BUF_LIMIT, HEADER_SIZE,
    MAGIC_HEADER, PUBLIC_KEY_LENGTH, SIGNATURE_LENGTH,
};

/// An error returned by [`collect_keys()`]
#[derive(Debug, thiserror::Error)]
pub enum CollectKeysError {
    /// The input was empty
    #[error("the input was empty")]
    Empty,
    /// Could not read a key
    #[error("could not read key #{1}")]
    Io(#[source] std::io::Error, usize),
    /// Input contained an illegal key
    #[error("input contained an illegal key at #{1}")]
    Signature(#[source] SignatureError, usize),
}

/// Convert a slice of key bytes into a [`Vec`] of [`VerifyingKey`]s.
pub fn collect_keys<K>(keys: K) -> Result<Vec<VerifyingKey>, CollectKeysError>
where
    K: IntoIterator<Item = std::io::Result<[u8; PUBLIC_KEY_LENGTH]>>,
{
    let keys = keys
        .into_iter()
        .enumerate()
        .map(|(idx, key)| {
            let key = key.map_err(|err| CollectKeysError::Io(err, idx))?;
            VerifyingKey::from_bytes(&key).map_err(|err| CollectKeysError::Signature(err, idx))
        })
        .collect::<Result<Vec<_>, _>>()?;
    if keys.is_empty() {
        return Err(CollectKeysError::Empty);
    }
    Ok(keys)
}

/// No matching key/signature pair found
#[derive(Debug, Clone, Copy, thiserror::Error)]
#[error("no matching key/signature pair found")]
pub struct NoMatch;

/// Iterate [signatures][Signature] and [keys][VerifyingKey] and return the indices of the first
/// match
pub fn find_match(
    keys: &[VerifyingKey],
    signatures: &[Signature],
    prehashed_message: &Sha512,
    context: Option<&[u8]>,
) -> Result<(usize, usize), NoMatch> {
    for (key_idx, key) in keys.iter().enumerate() {
        for (sig_idx, signature) in signatures.iter().enumerate() {
            let is_ok = key
                .verify_prehashed_strict(prehashed_message.clone(), context, signature)
                .is_ok();
            if is_ok {
                return Ok((key_idx, sig_idx));
            }
        }
    }
    Err(NoMatch)
}

/// An error returned by [`read_signatures()`]
#[derive(Debug, thiserror::Error)]
pub enum ReadSignaturesError {
    /// The input contained no signatures
    #[error("the input contained no signatures")]
    Empty,
    /// Could not read signatures
    #[error("could not read signatures")]
    Read(#[source] std::io::Error),
    /// The expected magic header was missing or corrupted
    #[error("the expected magic header was missing or corrupted")]
    MagicHeader,
    /// Input contained an illegal signature
    #[error("input contained an illegal signature at #{1}")]
    Signature(#[source] SignatureError, usize),
}

/// Collect all signatures in a file
pub fn read_signatures<I>(input: &mut I) -> Result<Vec<Signature>, ReadSignaturesError>
where
    I: ?Sized + Read,
{
    let mut header = [0; HEADER_SIZE];
    input
        .read_exact(&mut header)
        .map_err(ReadSignaturesError::Read)?;
    if header[..MAGIC_HEADER.len()] != *MAGIC_HEADER {
        return Err(ReadSignaturesError::MagicHeader);
    }

    let signature_count = header[MAGIC_HEADER.len()..].try_into().unwrap();
    let signature_count = SignatureCountLeInt::from_le_bytes(signature_count) as usize;
    if signature_count == 0 {
        return Err(ReadSignaturesError::Empty);
    }
    let signature_bytes = signature_count * SIGNATURE_LENGTH;
    if signature_bytes > BUF_LIMIT {
        return Err(ReadSignaturesError::MagicHeader);
    }

    let mut signatures = vec![0; signature_bytes];
    input
        .read_exact(&mut signatures)
        .map_err(ReadSignaturesError::Read)?;

    let signatures = signatures
        .chunks_exact(SIGNATURE_LENGTH)
        .enumerate()
        .map(|(idx, bytes)| {
            Signature::from_slice(bytes).map_err(|err| ReadSignaturesError::Signature(err, idx))
        })
        .collect::<Result<Vec<_>, _>>()?;

    Ok(signatures)
}