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|
/// Decrypts asymmetrically-encrypted OpenPGP messages using the
/// openpgp crate, Sequoia's low-level API.
use std::sync::Arc;
use std::collections::HashMap;
use std::env;
use std::io;
use anyhow::Context;
use sequoia_openpgp as openpgp;
use openpgp::*;
use openpgp::crypto::{KeyPair, SessionKey};
use openpgp::types::SymmetricAlgorithm;
use openpgp::parse::{
Parse,
stream::{
DecryptionHelper,
DecryptorBuilder,
VerificationHelper,
GoodChecksum,
MessageStructure,
MessageLayer,
},
};
use openpgp::policy::Policy;
use openpgp::policy::StandardPolicy as P;
pub fn main() -> openpgp::Result<()> {
let p = &P::new();
let args: Vec<String> = env::args().collect();
if args.len() < 2 {
return Err(anyhow::anyhow!("A simple decryption filter.\n\n\
Usage: {} <keyfile> [<keyfile>...] <input >output\n", args[0]));
}
// Read the transferable secret keys from the given files.
let certs =
args[1..].iter().map(|f| {
openpgp::Cert::from_file(f)
}).collect::<openpgp::Result<Vec<_>>>()
.context("Failed to read key")?;
// Now, create a decryptor with a helper using the given Certs.
let mut decryptor =
DecryptorBuilder::from_reader(io::stdin())?
.with_policy(p, None, Helper::new(p, certs))?;
// Finally, stream the decrypted data to stdout.
io::copy(&mut decryptor, &mut io::stdout())
.context("Decryption failed")?;
Ok(())
}
/// This helper provides secrets for the decryption, fetches public
/// keys for the signature verification and implements the
/// verification policy.
struct Helper {
keys: HashMap<KeyID, (Arc<Cert>, KeyPair)>,
}
impl Helper {
/// Creates a Helper for the given Certs with appropriate secrets.
fn new(p: &dyn Policy, certs: Vec<openpgp::Cert>) -> Self {
// Map (sub)KeyIDs to certs and secrets.
let mut keys = HashMap::new();
for cert in certs {
let cert = Arc::new(cert);
for ka in cert.keys().unencrypted_secret().with_policy(p, None)
.supported()
.for_storage_encryption().for_transport_encryption()
{
keys.insert(ka.key().keyid(),
(cert.clone(),
ka.key().clone().into_keypair().unwrap()));
}
}
Helper {
keys,
}
}
}
impl DecryptionHelper for Helper {
fn decrypt(&mut self,
pkesks: &[openpgp::packet::PKESK],
_skesks: &[openpgp::packet::SKESK],
sym_algo: Option<SymmetricAlgorithm>,
decrypt: &mut dyn FnMut(Option<SymmetricAlgorithm>, &SessionKey) -> bool)
-> openpgp::Result<Option<Cert>>
{
// Try each PKESK until we succeed.
let mut recipient = None;
for pkesk in pkesks {
if let Some((cert, pair)) = self.keys.get_mut(&KeyID::from(pkesk.recipient())) {
if pkesk.decrypt(pair, sym_algo)
.map(|(algo, session_key)| decrypt(algo, &session_key))
.unwrap_or(false)
{
recipient = Some(cert.as_ref().clone());
break;
}
}
}
Ok(recipient)
}
}
impl VerificationHelper for Helper {
fn get_certs(&mut self, _ids: &[openpgp::KeyHandle])
-> openpgp::Result<Vec<openpgp::Cert>> {
Ok(Vec::new()) // Feed the Certs to the verifier here.
}
fn check(&mut self, structure: MessageStructure)
-> openpgp::Result<()> {
for layer in structure.iter() {
match layer {
MessageLayer::Compression { algo } =>
eprintln!("Compressed using {}", algo),
MessageLayer::Encryption { sym_algo, aead_algo } =>
if let Some(aead_algo) = aead_algo {
eprintln!("Encrypted and protected using {}/{}",
sym_algo, aead_algo);
} else {
eprintln!("Encrypted using {}", sym_algo);
},
MessageLayer::SignatureGroup { ref results } =>
for result in results {
match result {
Ok(GoodChecksum { ka, .. }) => {
eprintln!("Good signature from {}", ka.cert());
},
Err(e) =>
eprintln!("Error: {:?}", e),
}
}
}
}
Ok(()) // Implement your verification policy here.
}
}
|
