From 92904ac94e4309103d0661e472cad3a9f78c558c Mon Sep 17 00:00:00 2001
From: Justus Winter <justus@sequoia-pgp.org>
Date: Thu, 5 Jul 2018 11:42:11 +0200
Subject: openpgp: Add simple decryption example.

---
 openpgp/examples/decrypt-with.rs | 121 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 openpgp/examples/decrypt-with.rs

(limited to 'openpgp/examples/decrypt-with.rs')

diff --git a/openpgp/examples/decrypt-with.rs b/openpgp/examples/decrypt-with.rs
new file mode 100644
index 00000000..3ffaa0a3
--- /dev/null
+++ b/openpgp/examples/decrypt-with.rs
@@ -0,0 +1,121 @@
+/// This program demonstrates how to decrypt a stream of data.
+
+use std::env;
+use std::io;
+use std::collections::HashMap;
+
+extern crate openpgp;
+use openpgp::{
+    Packet,
+    KeyID,
+    Key,
+    TPK,
+    SecretKey,
+};
+use openpgp::parse::PacketParserResult;
+
+pub fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() < 2 {
+        panic!("A simple decryption filter.\n\n\
+                Usage: {} <keyfile> [<keyfile>...] <input >output\n", args[0]);
+    }
+
+    // Read the transferable secret keys from the given files.
+    let mut keys: HashMap<KeyID, Key> = HashMap::new();
+    for f in args[1..].iter() {
+        let tsk = TPK::from_reader(
+            // Use an openpgp::Reader so that we accept both armored
+            // and plain PGP data.
+            openpgp::Reader::from_file(f)
+                .expect("Failed to open file"))
+            .expect("Failed to read key");
+        for key in tsk.keys() {
+            // XXX this is cheating, we just add all keys, even if
+            // they should not be used for encryption
+            keys.insert(key.fingerprint().to_keyid(), key.clone());
+        }
+    }
+
+    #[derive(PartialEq)]
+    enum State {
+        Start(Vec<openpgp::PKESK>, Vec<openpgp::SKESK>),
+        Deciphered,
+        Done,
+    }
+    let mut state = State::Start(vec![], vec![]);
+    let mut input = io::stdin();
+    let mut ppr
+        = openpgp::parse::PacketParser::from_reader(
+            openpgp::Reader::from_reader(&mut input)
+                .expect("Failed to build reader"))
+        .expect("Failed to build parser");
+
+    while let PacketParserResult::Some(mut pp) = ppr {
+        state = match state {
+            // Look for an PKESK or SKESK packet.
+            State::Start(mut pkesks, mut skesks) =>
+                match pp.packet {
+                    Packet::SEIP(_) => {
+                        let mut state = None;
+                        for pkesk in pkesks.iter() {
+                            if let Some(tsk) = keys.get(&pkesk.recipient) {
+                                if let Some(SecretKey::Unencrypted{ref mpis}) = tsk.secret {
+                                    if let Ok((algo, key)) = pkesk.decrypt(tsk, mpis) {
+	                                let r = pp.decrypt(algo, &key[..]);
+                                        if r.is_ok() {
+                                            state = Some(State::Deciphered);
+                                            break;
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                        state.unwrap_or(State::Start(pkesks, skesks))
+                    },
+                    _ => State::Start(pkesks, skesks),
+                },
+
+            // Look for the literal data packet.
+            State::Deciphered =>
+                if let Packet::Literal(_) = pp.packet {
+                    io::copy(&mut pp, &mut io::stdout())
+                        .expect("Failed to copy data");
+                    State::Done
+                } else {
+                    State::Deciphered
+                },
+
+            // We continue to parse, useful for dumping
+            // encrypted packets.
+            State::Done => State::Done,
+        };
+
+        let (packet, _, ppr_tmp, _) = pp.recurse()
+            .expect("Failed to recurse");
+        ppr = ppr_tmp;
+
+        state = match state {
+            // Look for an PKESK or SKESK packet.
+            State::Start(mut pkesks, mut skesks) =>
+                match packet {
+                    Packet::PKESK(pkesk) => {
+                        pkesks.push(pkesk);
+                        State::Start(pkesks, skesks)
+                    },
+                    Packet::SKESK(skesk) => {
+                        skesks.push(skesk);
+                        State::Start(pkesks, skesks)
+                    },
+                    _ => State::Start(pkesks, skesks),
+                },
+
+            // Do nothing in all other states.
+            s => s,
+        };
+    }
+
+    if state != State::Done {
+        panic!("decryption failed");
+    }
+}
-- 
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