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#![forbid(unsafe_code, unstable_features)]
#![deny(
trivial_casts,
trivial_numeric_casts,
missing_docs,
unused_import_braces,
unused_extern_crates,
unused_qualifications
)]
#![no_std]
extern crate alloc;
use alloc::{vec, vec::Vec};
#[derive(Debug)]
pub struct Log<'a> {
pub description: &'a str,
pub url: &'a str,
pub operated_by: &'a str,
pub key: &'a [u8],
pub id: [u8; 32],
pub max_merge_delay: usize,
}
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Error {
MalformedSct,
InvalidSignature,
TimestampInFuture,
UnsupportedSctVersion,
UnknownLog,
}
impl Error {
pub fn should_be_fatal(&self) -> bool {
!matches!(self, Error::UnknownLog | Error::UnsupportedSctVersion)
}
}
fn lookup(logs: &[&Log], id: &[u8]) -> Result<usize, Error> {
for (i, l) in logs.iter().enumerate() {
if id == l.id {
return Ok(i);
}
}
Err(Error::UnknownLog)
}
fn decode_u64(inp: untrusted::Input) -> u64 {
let b = inp.as_slice_less_safe();
assert_eq!(b.len(), 8);
(b[0] as u64) << 56
| (b[1] as u64) << 48
| (b[2] as u64) << 40
| (b[3] as u64) << 32
| (b[4] as u64) << 24
| (b[5] as u64) << 16
| (b[6] as u64) << 8
| (b[7] as u64)
}
fn decode_u16(inp: untrusted::Input) -> u16 {
let b = inp.as_slice_less_safe();
assert_eq!(b.len(), 2);
(b[0] as u16) << 8 | (b[1] as u16)
}
fn write_u64(v: u64, out: &mut Vec<u8>) {
out.push((v >> 56) as u8);
out.push((v >> 48) as u8);
out.push((v >> 40) as u8);
out.push((v >> 32) as u8);
out.push((v >> 24) as u8);
out.push((v >> 16) as u8);
out.push((v >> 8) as u8);
out.push(v as u8);
}
fn write_u24(v: u32, out: &mut Vec<u8>) {
out.push((v >> 16) as u8);
out.push((v >> 8) as u8);
out.push(v as u8);
}
fn write_u16(v: u16, out: &mut Vec<u8>) {
out.push((v >> 8) as u8);
out.push(v as u8);
}
struct Sct<'a> {
log_id: &'a [u8],
timestamp: u64,
sig_alg: u16,
sig: &'a [u8],
exts: &'a [u8],
}
const ECDSA_SHA256: u16 = 0x0403;
const ECDSA_SHA384: u16 = 0x0503;
const RSA_PKCS1_SHA256: u16 = 0x0401;
const RSA_PKCS1_SHA384: u16 = 0x0501;
const SCT_V1: u8 = 0u8;
const SCT_TIMESTAMP: u8 = 0u8;
const SCT_X509_ENTRY: [u8; 2] = [0, 0];
impl<'a> Sct<'a> {
fn verify(&self, key: &[u8], cert: &[u8]) -> Result<(), Error> {
let alg: &dyn ring::signature::VerificationAlgorithm = match self.sig_alg {
ECDSA_SHA256 => &ring::signature::ECDSA_P256_SHA256_ASN1,
ECDSA_SHA384 => &ring::signature::ECDSA_P384_SHA384_ASN1,
RSA_PKCS1_SHA256 => &ring::signature::RSA_PKCS1_2048_8192_SHA256,
RSA_PKCS1_SHA384 => &ring::signature::RSA_PKCS1_2048_8192_SHA384,
_ => return Err(Error::InvalidSignature),
};
let mut data = vec![SCT_V1, SCT_TIMESTAMP];
write_u64(self.timestamp, &mut data);
data.extend_from_slice(&SCT_X509_ENTRY);
write_u24(cert.len() as u32, &mut data);
data.extend_from_slice(cert);
write_u16(self.exts.len() as u16, &mut data);
data.extend_from_slice(self.exts);
let key = ring::signature::UnparsedPublicKey::new(alg, key);
key.verify(&data, self.sig)
.map_err(|_| Error::InvalidSignature)
}
fn parse(enc: &'a [u8]) -> Result<Sct<'a>, Error> {
let inp = untrusted::Input::from(enc);
inp.read_all(Error::MalformedSct, |rd| {
let version = rd
.read_byte()
.map_err(|_| Error::MalformedSct)?;
if version != 0 {
return Err(Error::UnsupportedSctVersion);
}
let id = rd
.read_bytes(32)
.map_err(|_| Error::MalformedSct)?;
let timestamp = rd
.read_bytes(8)
.map_err(|_| Error::MalformedSct)
.map(decode_u64)?;
let ext_len = rd
.read_bytes(2)
.map_err(|_| Error::MalformedSct)
.map(decode_u16)?;
let exts = rd
.read_bytes(ext_len as usize)
.map_err(|_| Error::MalformedSct)?;
let sig_alg = rd
.read_bytes(2)
.map_err(|_| Error::MalformedSct)
.map(decode_u16)?;
let sig_len = rd
.read_bytes(2)
.map_err(|_| Error::MalformedSct)
.map(decode_u16)?;
let sig = rd
.read_bytes(sig_len as usize)
.map_err(|_| Error::MalformedSct)?;
let ret = Sct {
log_id: id.as_slice_less_safe(),
timestamp,
sig_alg,
sig: sig.as_slice_less_safe(),
exts: exts.as_slice_less_safe(),
};
Ok(ret)
})
}
}
pub fn verify_sct(cert: &[u8], sct: &[u8], at_time: u64, logs: &[&Log]) -> Result<usize, Error> {
let sct = Sct::parse(sct)?;
let i = lookup(logs, &sct.log_id)?;
let log = logs[i];
sct.verify(log.key, cert)?;
if sct.timestamp > at_time {
return Err(Error::TimestampInFuture);
}
Ok(i)
}
#[cfg(test)]
mod tests;
#[cfg(test)]
mod tests_generated;
#[cfg(test)]
mod tests_google;