deltachat/imex/
key_transfer.rs

1//! # Key transfer via Autocrypt Setup Message.
2use std::io::BufReader;
3
4use rand::{Rng, thread_rng};
5
6use anyhow::{Result, bail, ensure};
7
8use crate::blob::BlobObject;
9use crate::chat::{self, ChatId};
10use crate::config::Config;
11use crate::constants::{ASM_BODY, ASM_SUBJECT};
12use crate::contact::ContactId;
13use crate::context::Context;
14use crate::imex::set_self_key;
15use crate::key::{DcKey, load_self_secret_key};
16use crate::message::{Message, MsgId, Viewtype};
17use crate::mimeparser::SystemMessage;
18use crate::param::Param;
19use crate::pgp;
20use crate::tools::open_file_std;
21
22/// Initiates key transfer via Autocrypt Setup Message.
23///
24/// Returns setup code.
25pub async fn initiate_key_transfer(context: &Context) -> Result<String> {
26    let setup_code = create_setup_code(context);
27    /* this may require a keypair to be created. this may take a second ... */
28    let setup_file_content = render_setup_file(context, &setup_code).await?;
29    /* encrypting may also take a while ... */
30    let setup_file_blob = BlobObject::create_and_deduplicate_from_bytes(
31        context,
32        setup_file_content.as_bytes(),
33        "autocrypt-setup-message.html",
34    )?;
35
36    let chat_id = ChatId::create_for_contact(context, ContactId::SELF).await?;
37    let mut msg = Message::new(Viewtype::File);
38    msg.param.set(Param::File, setup_file_blob.as_name());
39    msg.param
40        .set(Param::Filename, "autocrypt-setup-message.html");
41    msg.subject = ASM_SUBJECT.to_owned();
42    msg.param
43        .set(Param::MimeType, "application/autocrypt-setup");
44    msg.param.set_cmd(SystemMessage::AutocryptSetupMessage);
45    msg.force_plaintext();
46    msg.param.set_int(Param::SkipAutocrypt, 1);
47
48    // Enable BCC-self, because transferring a key
49    // means we have a multi-device setup.
50    context.set_config_bool(Config::BccSelf, true).await?;
51
52    chat::send_msg(context, chat_id, &mut msg).await?;
53    Ok(setup_code)
54}
55
56/// Continue key transfer via Autocrypt Setup Message.
57///
58/// `msg_id` is the ID of the received Autocrypt Setup Message.
59/// `setup_code` is the code entered by the user.
60pub async fn continue_key_transfer(
61    context: &Context,
62    msg_id: MsgId,
63    setup_code: &str,
64) -> Result<()> {
65    ensure!(!msg_id.is_special(), "wrong id");
66
67    let msg = Message::load_from_db(context, msg_id).await?;
68    ensure!(
69        msg.is_setupmessage(),
70        "Message is no Autocrypt Setup Message."
71    );
72
73    if let Some(filename) = msg.get_file(context) {
74        let file = open_file_std(context, filename)?;
75        let sc = normalize_setup_code(setup_code);
76        let armored_key = decrypt_setup_file(&sc, BufReader::new(file)).await?;
77        set_self_key(context, &armored_key).await?;
78        context.set_config_bool(Config::BccSelf, true).await?;
79
80        Ok(())
81    } else {
82        bail!("Message is no Autocrypt Setup Message.");
83    }
84}
85
86/// Renders HTML body of a setup file message.
87///
88/// The `passphrase` must be at least 2 characters long.
89pub async fn render_setup_file(context: &Context, passphrase: &str) -> Result<String> {
90    let passphrase_begin = if let Some(passphrase_begin) = passphrase.get(..2) {
91        passphrase_begin
92    } else {
93        bail!("Passphrase must be at least 2 chars long.");
94    };
95    let private_key = load_self_secret_key(context).await?;
96    let ac_headers = Some(("Autocrypt-Prefer-Encrypt", "mutual"));
97    let private_key_asc = private_key.to_asc(ac_headers);
98    let encr = pgp::symm_encrypt(passphrase, private_key_asc.into_bytes())
99        .await?
100        .replace('\n', "\r\n");
101
102    let replacement = format!(
103        concat!(
104            "-----BEGIN PGP MESSAGE-----\r\n",
105            "Passphrase-Format: numeric9x4\r\n",
106            "Passphrase-Begin: {}"
107        ),
108        passphrase_begin
109    );
110    let pgp_msg = encr.replace("-----BEGIN PGP MESSAGE-----", &replacement);
111
112    let msg_subj = ASM_SUBJECT;
113    let msg_body = ASM_BODY.to_string();
114    let msg_body_html = msg_body.replace('\r', "").replace('\n', "<br>");
115    Ok(format!(
116        concat!(
117            "<!DOCTYPE html>\r\n",
118            "<html>\r\n",
119            "  <head>\r\n",
120            "    <title>{}</title>\r\n",
121            "  </head>\r\n",
122            "  <body>\r\n",
123            "    <h1>{}</h1>\r\n",
124            "    <p>{}</p>\r\n",
125            "    <pre>\r\n{}\r\n</pre>\r\n",
126            "  </body>\r\n",
127            "</html>\r\n"
128        ),
129        msg_subj, msg_subj, msg_body_html, pgp_msg
130    ))
131}
132
133/// Creates a new setup code for Autocrypt Setup Message.
134fn create_setup_code(_context: &Context) -> String {
135    let mut random_val: u16;
136    let mut rng = thread_rng();
137    let mut ret = String::new();
138
139    for i in 0..9 {
140        loop {
141            random_val = rng.r#gen();
142            if random_val as usize <= 60000 {
143                break;
144            }
145        }
146        random_val = (random_val as usize % 10000) as u16;
147        ret += &format!(
148            "{}{:04}",
149            if 0 != i { "-" } else { "" },
150            random_val as usize
151        );
152    }
153
154    ret
155}
156
157async fn decrypt_setup_file<T: std::fmt::Debug + std::io::BufRead + Send + 'static>(
158    passphrase: &str,
159    file: T,
160) -> Result<String> {
161    let plain_bytes = pgp::symm_decrypt(passphrase, file).await?;
162    let plain_text = std::string::String::from_utf8(plain_bytes)?;
163
164    Ok(plain_text)
165}
166
167fn normalize_setup_code(s: &str) -> String {
168    let mut out = String::new();
169    for c in s.chars() {
170        if c.is_ascii_digit() {
171            out.push(c);
172            if let 4 | 9 | 14 | 19 | 24 | 29 | 34 | 39 = out.len() {
173                out += "-"
174            }
175        }
176    }
177    out
178}
179
180#[cfg(test)]
181mod tests {
182    use super::*;
183
184    use crate::pgp::{HEADER_AUTOCRYPT, HEADER_SETUPCODE, split_armored_data};
185    use crate::receive_imf::receive_imf;
186    use crate::test_utils::{TestContext, TestContextManager};
187    use ::pgp::armor::BlockType;
188
189    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
190    async fn test_render_setup_file() {
191        let t = TestContext::new_alice().await;
192        let msg = render_setup_file(&t, "hello").await.unwrap();
193        println!("{}", &msg);
194        // Check some substrings, indicating things got substituted.
195        assert!(msg.contains("<title>Autocrypt Setup Message</title"));
196        assert!(msg.contains("<h1>Autocrypt Setup Message</h1>"));
197        assert!(msg.contains("<p>This is the Autocrypt Setup Message used to"));
198        assert!(msg.contains("-----BEGIN PGP MESSAGE-----\r\n"));
199        assert!(msg.contains("Passphrase-Format: numeric9x4\r\n"));
200        assert!(msg.contains("Passphrase-Begin: he\r\n"));
201        assert!(msg.contains("-----END PGP MESSAGE-----\r\n"));
202
203        for line in msg.rsplit_terminator('\n') {
204            assert!(line.ends_with('\r'));
205        }
206    }
207
208    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
209    async fn test_render_setup_file_newline_replace() {
210        let t = TestContext::new_alice().await;
211        let msg = render_setup_file(&t, "pw").await.unwrap();
212        println!("{}", &msg);
213        assert!(msg.contains("<p>This is the Autocrypt Setup Message used to transfer your end-to-end setup between clients.<br>"));
214    }
215
216    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
217    async fn test_create_setup_code() {
218        let t = TestContext::new().await;
219        let setupcode = create_setup_code(&t);
220        assert_eq!(setupcode.len(), 44);
221        assert_eq!(setupcode.chars().nth(4).unwrap(), '-');
222        assert_eq!(setupcode.chars().nth(9).unwrap(), '-');
223        assert_eq!(setupcode.chars().nth(14).unwrap(), '-');
224        assert_eq!(setupcode.chars().nth(19).unwrap(), '-');
225        assert_eq!(setupcode.chars().nth(24).unwrap(), '-');
226        assert_eq!(setupcode.chars().nth(29).unwrap(), '-');
227        assert_eq!(setupcode.chars().nth(34).unwrap(), '-');
228        assert_eq!(setupcode.chars().nth(39).unwrap(), '-');
229    }
230
231    #[test]
232    fn test_normalize_setup_code() {
233        let norm = normalize_setup_code("123422343234423452346234723482349234");
234        assert_eq!(norm, "1234-2234-3234-4234-5234-6234-7234-8234-9234");
235
236        let norm =
237            normalize_setup_code("\t1 2 3422343234- foo bar-- 423-45 2 34 6234723482349234      ");
238        assert_eq!(norm, "1234-2234-3234-4234-5234-6234-7234-8234-9234");
239    }
240
241    /* S_EM_SETUPFILE is a AES-256 symm. encrypted setup message created by Enigmail
242    with an "encrypted session key", see RFC 4880.  The code is in S_EM_SETUPCODE */
243    const S_EM_SETUPCODE: &str = "1742-0185-6197-1303-7016-8412-3581-4441-0597";
244    const S_EM_SETUPFILE: &str = include_str!("../../test-data/message/stress.txt");
245
246    // Autocrypt Setup Message payload "encrypted" with plaintext algorithm.
247    const S_PLAINTEXT_SETUPFILE: &str =
248        include_str!("../../test-data/message/plaintext-autocrypt-setup.txt");
249
250    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
251    async fn test_split_and_decrypt() {
252        let buf_1 = S_EM_SETUPFILE.as_bytes().to_vec();
253        let (typ, headers, base64) = split_armored_data(&buf_1).unwrap();
254        assert_eq!(typ, BlockType::Message);
255        assert!(S_EM_SETUPCODE.starts_with(headers.get(HEADER_SETUPCODE).unwrap()));
256        assert!(!headers.contains_key(HEADER_AUTOCRYPT));
257
258        assert!(!base64.is_empty());
259
260        let setup_file = S_EM_SETUPFILE;
261        let decrypted = decrypt_setup_file(S_EM_SETUPCODE, setup_file.as_bytes())
262            .await
263            .unwrap();
264
265        let (typ, headers, _base64) = split_armored_data(decrypted.as_bytes()).unwrap();
266
267        assert_eq!(typ, BlockType::PrivateKey);
268        assert_eq!(headers.get(HEADER_AUTOCRYPT), Some(&"mutual".to_string()));
269        assert!(!headers.contains_key(HEADER_SETUPCODE));
270    }
271
272    /// Tests that Autocrypt Setup Message encrypted with "plaintext" algorithm cannot be
273    /// decrypted.
274    ///
275    /// According to <https://datatracker.ietf.org/doc/html/rfc4880#section-13.4>
276    /// "Implementations MUST NOT use plaintext in Symmetrically Encrypted Data packets".
277    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
278    async fn test_decrypt_plaintext_autocrypt_setup_message() {
279        let setup_file = S_PLAINTEXT_SETUPFILE;
280        let incorrect_setupcode = "0000-0000-0000-0000-0000-0000-0000-0000-0000";
281        assert!(
282            decrypt_setup_file(incorrect_setupcode, setup_file.as_bytes(),)
283                .await
284                .is_err()
285        );
286    }
287
288    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
289    async fn test_key_transfer() -> Result<()> {
290        let mut tcm = TestContextManager::new();
291        let alice = &tcm.alice().await;
292
293        tcm.section("Alice sends Autocrypt setup message");
294        alice.set_config(Config::BccSelf, Some("0")).await?;
295        let setup_code = initiate_key_transfer(alice).await?;
296
297        // Test that sending Autocrypt Setup Message enables `bcc_self`.
298        assert_eq!(alice.get_config_bool(Config::BccSelf).await?, true);
299
300        // Get Autocrypt Setup Message.
301        let sent = alice.pop_sent_msg().await;
302
303        tcm.section("Alice sets up a second device");
304        let alice2 = &tcm.unconfigured().await;
305        alice2.set_name("alice2");
306        alice2.configure_addr("alice@example.org").await;
307        alice2.recv_msg(&sent).await;
308        let msg = alice2.get_last_msg().await;
309        assert!(msg.is_setupmessage());
310        assert_eq!(crate::key::load_self_secret_keyring(alice2).await?.len(), 0);
311
312        // Transfer the key.
313        tcm.section("Alice imports a key from Autocrypt Setup Message");
314        alice2.set_config(Config::BccSelf, Some("0")).await?;
315        continue_key_transfer(alice2, msg.id, &setup_code).await?;
316        assert_eq!(alice2.get_config_bool(Config::BccSelf).await?, true);
317        assert_eq!(crate::key::load_self_secret_keyring(alice2).await?.len(), 1);
318
319        // Alice sends a message to self from the new device.
320        let sent = alice2.send_text(msg.chat_id, "Test").await;
321        let rcvd_msg = alice.recv_msg(&sent).await;
322        assert_eq!(rcvd_msg.get_text(), "Test");
323
324        Ok(())
325    }
326
327    /// Tests that Autocrypt Setup Messages is only clickable if it is self-sent.
328    /// This prevents Bob from tricking Alice into changing the key
329    /// by sending her an Autocrypt Setup Message as long as Alice's server
330    /// does not allow to forge the `From:` header.
331    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
332    async fn test_key_transfer_non_self_sent() -> Result<()> {
333        let mut tcm = TestContextManager::new();
334        let alice = tcm.alice().await;
335        let bob = tcm.bob().await;
336
337        let _setup_code = initiate_key_transfer(&alice).await?;
338
339        // Get Autocrypt Setup Message.
340        let sent = alice.pop_sent_msg().await;
341
342        let rcvd = bob.recv_msg(&sent).await;
343        assert!(!rcvd.is_setupmessage());
344
345        Ok(())
346    }
347
348    /// Tests reception of Autocrypt Setup Message from K-9 6.802.
349    ///
350    /// Unlike Autocrypt Setup Message sent by Delta Chat,
351    /// this message does not contain `Autocrypt-Prefer-Encrypt` header.
352    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
353    async fn test_key_transfer_k_9() -> Result<()> {
354        let t = &TestContext::new().await;
355        t.configure_addr("autocrypt@nine.testrun.org").await;
356
357        let raw = include_bytes!("../../test-data/message/k-9-autocrypt-setup-message.eml");
358        let received = receive_imf(t, raw, false).await?.unwrap();
359
360        let setup_code = "0655-9868-8252-5455-4232-5158-1237-5333-2638";
361        continue_key_transfer(t, *received.msg_ids.last().unwrap(), setup_code).await?;
362
363        Ok(())
364    }
365}
deltachat/imex/key_transfer.rs

deltachat/imex/
key_transfer.rs
