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
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174

//! ASN.1 `INTEGER` support.

use crate::{
    Any, ByteSlice, Encodable, Encoder, Error, ErrorKind, Header, Length, Result, Tag, Tagged,
};
use core::convert::TryFrom;

impl TryFrom<Any<'_>> for i8 {
    type Error = Error;

    fn try_from(any: Any<'_>) -> Result<i8> {
        let tag = any.tag().assert_eq(Tag::Integer)?;

        match any.as_bytes() {
            [x] => Ok(*x as i8),
            _ => Err(ErrorKind::Length { tag }.into()),
        }
    }
}

impl Encodable for i8 {
    fn encoded_len(&self) -> Result<Length> {
        Header {
            tag: Tag::Integer,
            length: 1u8.into(),
        }
        .encoded_len()?
            + 1u8
    }

    fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
        Header {
            tag: Tag::Integer,
            length: 1u8.into(),
        }
        .encode(encoder)?;
        encoder.byte(*self as u8)
    }
}

impl Tagged for i8 {
    const TAG: Tag = Tag::Integer;
}

/// Raw ASN.1 `INTEGER` type.
///
/// Provides direct access to the underlying DER-encoded bytes which comprise
/// an integer value, intended for use cases like very large integers that are
/// used for cryptographic keys. It can be used in order to convert them to the
/// big integer representation of your choice.
///
/// Note that the [`Decodable`][`crate::Decodable`] and [`Encodable`] traits are
/// impl'd for Rust's integer primitive types ([`i8`] only for now) if you'd like
/// to work directly with an integer value rather than decoding it yourself.
///
/// # ⚠️ Important Usage Notes ⚠️
///
/// This type does *NOT* ensure the value is canonically encoded according to
/// DER's rules. If it's important for your use case that the message is valid
/// ASN.1 DER, you *MUST* validate the value is canonically encoded yourself.
// TODO(tarcieri): implement generic validation rules for arbitrary-sized integers
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub struct RawInteger<'a> {
    /// Inner value
    inner: ByteSlice<'a>,
}

impl<'a> RawInteger<'a> {
    /// Create a new [`RawInteger`] from a slice.
    pub fn new(slice: &'a [u8]) -> Result<Self> {
        ByteSlice::new(slice)
            .map(|inner| Self { inner })
            .map_err(|_| ErrorKind::Length { tag: Self::TAG }.into())
    }

    /// Borrow the inner byte slice.
    pub fn as_bytes(&self) -> &'a [u8] {
        self.inner.as_bytes()
    }
}

impl AsRef<[u8]> for RawInteger<'_> {
    fn as_ref(&self) -> &[u8] {
        self.as_bytes()
    }
}

impl<'a> From<&RawInteger<'a>> for RawInteger<'a> {
    fn from(value: &RawInteger<'a>) -> RawInteger<'a> {
        *value
    }
}

impl<'a> TryFrom<Any<'a>> for RawInteger<'a> {
    type Error = Error;

    fn try_from(any: Any<'a>) -> Result<RawInteger<'a>> {
        any.tag().assert_eq(Tag::Integer)?;
        Self::new(any.as_bytes())
    }
}

impl<'a> From<RawInteger<'a>> for Any<'a> {
    fn from(integer: RawInteger<'a>) -> Any<'a> {
        Any {
            tag: Tag::Integer,
            value: integer.inner,
        }
    }
}

impl<'a> Encodable for RawInteger<'a> {
    fn encoded_len(&self) -> Result<Length> {
        Any::from(*self).encoded_len()
    }

    fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
        Any::from(*self).encode(encoder)
    }
}

impl<'a> Tagged for RawInteger<'a> {
    const TAG: Tag = Tag::Integer;
}

#[cfg(test)]
mod tests {
    use crate::{Decodable, Encodable};

    // TODO(tarcieri): larger integer types
    #[test]
    fn decode_i8() {
        // 0
        let int = i8::from_bytes(&[0x02, 0x01, 0x00]).unwrap();
        assert_eq!(i8::from(int), 0);

        // 127
        let int = i8::from_bytes(&[0x02, 0x01, 0x7F]).unwrap();
        assert_eq!(i8::from(int), 127);

        // -128
        let int = i8::from_bytes(&[0x02, 0x01, 0x80]).unwrap();
        assert_eq!(i8::from(int), -128);
    }

    #[test]
    fn encode_i8() {
        let mut buffer = [0u8; 3];

        // 0
        assert_eq!(
            &[0x02, 0x01, 0x00],
            i8::from(0i8).encode_to_slice(&mut buffer).unwrap()
        );

        // 127
        assert_eq!(
            &[0x02, 0x01, 0x7F],
            i8::from(127i8).encode_to_slice(&mut buffer).unwrap()
        );

        // -128
        assert_eq!(
            &[0x02, 0x01, 0x80],
            i8::from(-128i8).encode_to_slice(&mut buffer).unwrap()
        );
    }

    /// Integers must be encoded with a minimum number of octets
    #[test]
    fn reject_non_canonical() {
        assert!(i8::from_bytes(&[0x02, 0x02, 0x00, 0x00]).is_err());
    }
}