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use num_bigint::BigUint;
use crate::common_types::{DnsSecAlgorithm, DnsSecAlgorithmKnown};
// ECC_GOST [RFC5933]
// RFC5702 still confirms this
const RSA_BITS_LIMIT: usize = 4096;
const RSA_BYTES_LIMIT: usize = RSA_BITS_LIMIT / 8;
fn parse_rsa(data: &[u8]) -> crate::errors::Result<PublicKey> {
failure::ensure!(!data.is_empty(), "RSA public key must be non-empty");
let exp_len: usize;
let offset: usize;
if data[0] == 0 {
failure::ensure!(data.len() >= 3, "RSA public key: unexpected end of data when decoding exponent length");
exp_len = (data[1] as usize) << 8 + (data[2] as usize);
offset = 3;
failure::ensure!(exp_len >= 256, "RSA public key: exponent length in long form but too small");
} else {
exp_len = data[0] as usize;
offset = 1;
}
assert!(exp_len > 0); // should be unreachable: 0 means two bytes, which are checked for >= 256
failure::ensure!(exp_len <= RSA_BYTES_LIMIT, "RSA public key: exponent too long (limit: {} bits)", RSA_BITS_LIMIT);
failure::ensure!(data.len() >= offset + exp_len, "RSA public key: unexpected end of data when reading exponent");
failure::ensure!(data[offset] != 0, "RSA public key: leading zero in exponent");
let exponent = BigUint::from_bytes_be(&data[offset..][..exp_len]);
let modulus_data = &data[offset..][exp_len..];
failure::ensure!(modulus_data.len() <= RSA_BYTES_LIMIT, "RSA public key: modulus too long (limit: {} bits)", RSA_BITS_LIMIT);
failure::ensure!(!modulus_data.is_empty(), "RSA public key: modulus empty");
failure::ensure!(modulus_data[offset] != 0, "RSA public key: leading zero in modulus");
let modulus = BigUint::from_bytes_be(modulus_data);
Ok(PublicKey::RSA {
exponent,
modulus,
})
}
#[allow(non_camel_case_types)]
pub enum PublicKey {
RSA { exponent: BigUint, modulus: BigUint },
ECDSAP256 { xy: Box<([u8; 32], [u8; 32])> },
ECDSAP384 { xy: Box<([u8; 48], [u8; 48])> },
ECC_GOST { xy: Box<([u8; 32], [u8; 32])> },
ED25519 { key: Box<[u8; 32]> },
ED448 { key: Box<[u8; 57]> },
}
impl PublicKey {
pub fn parse(algorithm: DnsSecAlgorithm, data: &[u8]) -> crate::errors::Result<Self> {
use DnsSecAlgorithmKnown::*;
let algorithm = algorithm.into_known().ok_or_else(|| failure::format_err!("Unknown algorithm"))?;
match algorithm {
DELETE|INDIRECT|PRIVATEDNS|PRIVATEOID => failure::bail!("Algorithm {:?} not used with actual key", algorithm),
RSAMD5|RSASHA1|RSASHA1_NSEC3_SHA1|RSASHA256|RSASHA512 => parse_rsa(data),
DH|DSA|DSA_NSEC3_SHA1 => failure::bail!("Algorithm {:?} not supported", algorithm),
ECDSAP256SHA256 => {
failure::ensure!(data.len() == 64, "Expected 64 bytes public key for ECDSAP256");
let mut x = [0u8; 32];
x.copy_from_slice(&data[..32]);
let mut y = [0u8; 32];
y.copy_from_slice(&data[32..]);
Ok(PublicKey::ECDSAP256 { xy: Box::new((x, y)) })
},
ECDSAP384SHA384 => {
failure::ensure!(data.len() == 96, "Expected 96 bytes public key for ECDSAP384");
let mut x = [0u8; 48];
x.copy_from_slice(&data[..48]);
let mut y = [0u8; 48];
y.copy_from_slice(&data[48..]);
Ok(PublicKey::ECDSAP384 { xy: Box::new((x, y)) })
},
ECC_GOST => {
failure::ensure!(data.len() == 64, "Expected 64 bytes public key for ECC_GOST");
let mut x = [0u8; 32];
x.copy_from_slice(&data[..32]);
let mut y = [0u8; 32];
y.copy_from_slice(&data[32..]);
Ok(PublicKey::ECC_GOST { xy: Box::new((x, y)) })
},
ED25519 => {
failure::ensure!(data.len() == 32, "Expected 32 bytes public key for ED25519");
let mut key = [0u8; 32];
key.copy_from_slice(data);
Ok(PublicKey::ED25519 { key: Box::new(key) })
},
ED448 => {
failure::ensure!(data.len() == 57, "Expected 57 bytes public key for ED448");
let mut key = [0u8; 57];
key.copy_from_slice(data);
Ok(PublicKey::ED448 { key: Box::new(key) })
},
}
}
pub fn bits(&self) -> Option<u32> {
match self {
PublicKey::RSA { modulus, .. } => Some(modulus.bits() as u32),
PublicKey::ECDSAP256 { .. } => Some(32*8),
PublicKey::ECDSAP384 { .. } => Some(48*8),
PublicKey::ECC_GOST { .. } => Some(32*8),
PublicKey::ED25519 { .. } => Some(32*8),
PublicKey::ED448 { .. } => Some(57*8),
}
}
}