Add decrypt and detach-sign examples

This should mirror the usage of `gpg --decrypt` and `gpg --detach
--sign`.

Cargo.toml

@@ -4,6 +4,7 @@
 
 [workspace]
 members = [
+    "openpgp-card-apps",
     "openpgp-card",
     "openpgp-card-sequoia",
     "pcsc",

openpgp-card-apps/Cargo.toml

@@ -0,0 +1,25 @@
+# SPDX-FileCopyrightText: 2021 Wiktor Kwapisiewicz <wiktor@metacode.biz>
+# SPDX-License-Identifier: MIT OR Apache-2.0
+
+[package]
+name = "openpgp-card-apps"
+description = "Examples and demos of apps utilizing openpgp-card-sequoia"
+license = "MIT OR Apache-2.0"
+version = "0.0.1"
+authors = ["Wiktor Kwapisiewicz <wiktor@metacode.biz>"]
+edition = "2018"
+repository = "https://gitlab.com/hkos/openpgp-card"
+documentation = "https://docs.rs/crate/openpgp-card-apps"
+
+[dependencies]
+sequoia-openpgp = "1.3"
+nettle = "7"
+openpgp-card = { path = "../openpgp-card", version = "0.0.4" }
+openpgp-card-pcsc = { path = "../pcsc", version = "0.0.4" }
+openpgp-card-scdc = { path = "../scdc", version = "0.0.2" }
+openpgp-card-sequoia = { path = "../openpgp-card-sequoia", version = "0.0.3" }
+chrono = "0.4"
+anyhow = "1"
+thiserror = "1"
+env_logger = "0.8"
+log = "0.4"

openpgp-card-apps/README.md

@@ -0,0 +1,43 @@
+<!--
+SPDX-FileCopyrightText: 2021 Wiktor Kwapisiewicz <wiktor@metacode.biz>
+SPDX-License-Identifier: MIT OR Apache-2.0
+-->
+
+**OpenPGP card usage with Sequoia PGP: Example apps**
+
+*Small GnuPG replacements*
+
+This crate can be used to decrypt OpenPGP data and to sign data
+producing OpenPGP data.
+
+First export the certificate that holds keys stored on the card:
+
+```
+$ gpg --export --armor $KEYID > cert.asc
+```
+
+Then create a test data, encrypted with GnuPG (as an example):
+
+```
+$ echo example data | gpg -ear $KEYID > encrypted.asc
+```
+
+And put the card PIN in a file called `pin`.
+
+And then use the crate for decryption:
+
+```
+$ cargo run --example decrypt $CARD_ID pin cert.asc < encrypted.asc
+```
+
+The `$CARD_ID` holds card ident that can be printed using `cargo
+run`. It's a string that looks like `0006:12345678`. Remember that if
+the GnuPG agent is holding an exclusive access to the card it will not
+show up. Unplugging and plugging the card again will relinquish
+GnuPG's agent's hold on the card.
+
+Signing works the same way:
+
+```
+$ echo data to be signed | cargo run --example detach-sign $CARD_ID pin cert.asc > signature.asc
+```

openpgp-card-apps/src/bin/decrypt.rs

@@ -0,0 +1,46 @@
+// SPDX-FileCopyrightText: 2021 Wiktor Kwapisiewicz <wiktor@metacode.biz>
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+use openpgp_card_pcsc::PcscClient;
+
+use openpgp_card_sequoia::card::Open;
+
+use openpgp::parse::{stream::DecryptorBuilder, Parse};
+use openpgp::policy::StandardPolicy;
+use openpgp::Cert;
+use sequoia_openpgp as openpgp;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let args = std::env::args().collect::<Vec<_>>();
+
+    if args.len() < 3 {
+        eprintln!("Usage: decrypt card-ident pin-file cert-file");
+        return Ok(());
+    }
+
+    let card_ident = &args[0];
+    let pin_file = &args[1];
+    let cert_file = &args[2];
+
+    let mut open = Open::open_card(PcscClient::open_by_ident(&card_ident)?)?;
+
+    let pin = std::fs::read_to_string(pin_file)?;
+
+    open.verify_user(&pin)?;
+
+    let mut user = open.user_card().unwrap();
+
+    let p = StandardPolicy::new();
+    let cert = Cert::from_file(cert_file)?;
+    let d = user.decryptor(&cert, &p)?;
+    let stdin = std::io::stdin();
+
+    let mut stdout = std::io::stdout();
+
+    let db = DecryptorBuilder::from_reader(stdin)?;
+    let mut decryptor = db.with_policy(&p, None, d)?;
+
+    std::io::copy(&mut decryptor, &mut stdout)?;
+
+    Ok(())
+}

openpgp-card-apps/src/bin/detach-sign.rs

@@ -0,0 +1,54 @@
+// SPDX-FileCopyrightText: 2021 Wiktor Kwapisiewicz <wiktor@metacode.biz>
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+use openpgp_card_pcsc::PcscClient;
+
+use openpgp_card_sequoia::card::Open;
+
+use openpgp::parse::Parse;
+use openpgp::policy::StandardPolicy;
+use openpgp::serialize::stream::{Armorer, Message, Signer};
+use openpgp::Cert;
+use sequoia_openpgp as openpgp;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let args = std::env::args().collect::<Vec<_>>();
+
+    if args.len() < 3 {
+        eprintln!("Usage: detach-sign card-ident pin-file cert-file");
+        return Ok(());
+    }
+
+    let test_card_ident = &args[0];
+    let pin_file = &args[1];
+    let cert_file = &args[2];
+
+    let mut open =
+        Open::open_card(PcscClient::open_by_ident(&test_card_ident)?)?;
+
+    let pin = std::fs::read_to_string(pin_file)?;
+
+    open.verify_user_for_signing(&pin)?;
+
+    let mut user = open.signing_card().unwrap();
+
+    let p = StandardPolicy::new();
+    let cert = Cert::from_file(cert_file)?;
+    let s = user.signer(&cert, &p)?;
+
+    let stdout = std::io::stdout();
+
+    let message = Message::new(stdout);
+
+    let message = Armorer::new(message).build()?;
+
+    let signer = Signer::new(message, s);
+
+    let mut signer = signer.detached().build()?;
+
+    std::io::copy(&mut std::io::stdin(), &mut signer)?;
+
+    signer.finalize()?;
+
+    Ok(())
+}