deltachat/imex/
key_transfer.rs

1//! # Key transfer via Autocrypt Setup Message.
2use rand::{thread_rng, Rng};
3
4use anyhow::{bail, ensure, Result};
5
6use crate::blob::BlobObject;
7use crate::chat::{self, ChatId};
8use crate::config::Config;
9use crate::constants::{ASM_BODY, ASM_SUBJECT};
10use crate::contact::ContactId;
11use crate::context::Context;
12use crate::imex::set_self_key;
13use crate::key::{load_self_secret_key, DcKey};
14use crate::message::{Message, MsgId, Viewtype};
15use crate::mimeparser::SystemMessage;
16use crate::param::Param;
17use crate::pgp;
18use crate::tools::open_file_std;
19
20/// Initiates key transfer via Autocrypt Setup Message.
21///
22/// Returns setup code.
23pub async fn initiate_key_transfer(context: &Context) -> Result<String> {
24    let setup_code = create_setup_code(context);
25    /* this may require a keypair to be created. this may take a second ... */
26    let setup_file_content = render_setup_file(context, &setup_code).await?;
27    /* encrypting may also take a while ... */
28    let setup_file_blob = BlobObject::create_and_deduplicate_from_bytes(
29        context,
30        setup_file_content.as_bytes(),
31        "autocrypt-setup-message.html",
32    )?;
33
34    let chat_id = ChatId::create_for_contact(context, ContactId::SELF).await?;
35    let mut msg = Message {
36        viewtype: Viewtype::File,
37        ..Default::default()
38    };
39    msg.param.set(Param::File, setup_file_blob.as_name());
40    msg.param
41        .set(Param::Filename, "autocrypt-setup-message.html");
42    msg.subject = ASM_SUBJECT.to_owned();
43    msg.param
44        .set(Param::MimeType, "application/autocrypt-setup");
45    msg.param.set_cmd(SystemMessage::AutocryptSetupMessage);
46    msg.force_plaintext();
47    msg.param.set_int(Param::SkipAutocrypt, 1);
48
49    // Enable BCC-self, because transferring a key
50    // means we have a multi-device setup.
51    context.set_config_bool(Config::BccSelf, true).await?;
52
53    chat::send_msg(context, chat_id, &mut msg).await?;
54    Ok(setup_code)
55}
56
57/// Continue key transfer via Autocrypt Setup Message.
58///
59/// `msg_id` is the ID of the received Autocrypt Setup Message.
60/// `setup_code` is the code entered by the user.
61pub async fn continue_key_transfer(
62    context: &Context,
63    msg_id: MsgId,
64    setup_code: &str,
65) -> Result<()> {
66    ensure!(!msg_id.is_special(), "wrong id");
67
68    let msg = Message::load_from_db(context, msg_id).await?;
69    ensure!(
70        msg.is_setupmessage(),
71        "Message is no Autocrypt Setup Message."
72    );
73
74    if let Some(filename) = msg.get_file(context) {
75        let file = open_file_std(context, filename)?;
76        let sc = normalize_setup_code(setup_code);
77        let armored_key = decrypt_setup_file(&sc, file).await?;
78        set_self_key(context, &armored_key).await?;
79        context.set_config_bool(Config::BccSelf, true).await?;
80
81        Ok(())
82    } else {
83        bail!("Message is no Autocrypt Setup Message.");
84    }
85}
86
87/// Renders HTML body of a setup file message.
88///
89/// The `passphrase` must be at least 2 characters long.
90pub async fn render_setup_file(context: &Context, passphrase: &str) -> Result<String> {
91    let passphrase_begin = if let Some(passphrase_begin) = passphrase.get(..2) {
92        passphrase_begin
93    } else {
94        bail!("Passphrase must be at least 2 chars long.");
95    };
96    let private_key = load_self_secret_key(context).await?;
97    let ac_headers = match context.get_config_bool(Config::E2eeEnabled).await? {
98        false => None,
99        true => Some(("Autocrypt-Prefer-Encrypt", "mutual")),
100    };
101    let private_key_asc = private_key.to_asc(ac_headers);
102    let encr = pgp::symm_encrypt(passphrase, private_key_asc.as_bytes())
103        .await?
104        .replace('\n', "\r\n");
105
106    let replacement = format!(
107        concat!(
108            "-----BEGIN PGP MESSAGE-----\r\n",
109            "Passphrase-Format: numeric9x4\r\n",
110            "Passphrase-Begin: {}"
111        ),
112        passphrase_begin
113    );
114    let pgp_msg = encr.replace("-----BEGIN PGP MESSAGE-----", &replacement);
115
116    let msg_subj = ASM_SUBJECT;
117    let msg_body = ASM_BODY.to_string();
118    let msg_body_html = msg_body.replace('\r', "").replace('\n', "<br>");
119    Ok(format!(
120        concat!(
121            "<!DOCTYPE html>\r\n",
122            "<html>\r\n",
123            "  <head>\r\n",
124            "    <title>{}</title>\r\n",
125            "  </head>\r\n",
126            "  <body>\r\n",
127            "    <h1>{}</h1>\r\n",
128            "    <p>{}</p>\r\n",
129            "    <pre>\r\n{}\r\n</pre>\r\n",
130            "  </body>\r\n",
131            "</html>\r\n"
132        ),
133        msg_subj, msg_subj, msg_body_html, pgp_msg
134    ))
135}
136
137/// Creates a new setup code for Autocrypt Setup Message.
138fn create_setup_code(_context: &Context) -> String {
139    let mut random_val: u16;
140    let mut rng = thread_rng();
141    let mut ret = String::new();
142
143    for i in 0..9 {
144        loop {
145            random_val = rng.gen();
146            if random_val as usize <= 60000 {
147                break;
148            }
149        }
150        random_val = (random_val as usize % 10000) as u16;
151        ret += &format!(
152            "{}{:04}",
153            if 0 != i { "-" } else { "" },
154            random_val as usize
155        );
156    }
157
158    ret
159}
160
161async fn decrypt_setup_file<T: std::io::Read + std::io::Seek>(
162    passphrase: &str,
163    file: T,
164) -> Result<String> {
165    let plain_bytes = pgp::symm_decrypt(passphrase, file).await?;
166    let plain_text = std::string::String::from_utf8(plain_bytes)?;
167
168    Ok(plain_text)
169}
170
171fn normalize_setup_code(s: &str) -> String {
172    let mut out = String::new();
173    for c in s.chars() {
174        if c.is_ascii_digit() {
175            out.push(c);
176            if let 4 | 9 | 14 | 19 | 24 | 29 | 34 | 39 = out.len() {
177                out += "-"
178            }
179        }
180    }
181    out
182}
183
184#[cfg(test)]
185mod tests {
186    use super::*;
187
188    use crate::pgp::{split_armored_data, HEADER_AUTOCRYPT, HEADER_SETUPCODE};
189    use crate::receive_imf::receive_imf;
190    use crate::test_utils::{TestContext, TestContextManager};
191    use ::pgp::armor::BlockType;
192
193    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
194    async fn test_render_setup_file() {
195        let t = TestContext::new_alice().await;
196        let msg = render_setup_file(&t, "hello").await.unwrap();
197        println!("{}", &msg);
198        // Check some substrings, indicating things got substituted.
199        assert!(msg.contains("<title>Autocrypt Setup Message</title"));
200        assert!(msg.contains("<h1>Autocrypt Setup Message</h1>"));
201        assert!(msg.contains("<p>This is the Autocrypt Setup Message used to"));
202        assert!(msg.contains("-----BEGIN PGP MESSAGE-----\r\n"));
203        assert!(msg.contains("Passphrase-Format: numeric9x4\r\n"));
204        assert!(msg.contains("Passphrase-Begin: he\r\n"));
205        assert!(msg.contains("-----END PGP MESSAGE-----\r\n"));
206
207        for line in msg.rsplit_terminator('\n') {
208            assert!(line.ends_with('\r'));
209        }
210    }
211
212    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
213    async fn test_render_setup_file_newline_replace() {
214        let t = TestContext::new_alice().await;
215        let msg = render_setup_file(&t, "pw").await.unwrap();
216        println!("{}", &msg);
217        assert!(msg.contains("<p>This is the Autocrypt Setup Message used to transfer your end-to-end setup between clients.<br>"));
218    }
219
220    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
221    async fn test_create_setup_code() {
222        let t = TestContext::new().await;
223        let setupcode = create_setup_code(&t);
224        assert_eq!(setupcode.len(), 44);
225        assert_eq!(setupcode.chars().nth(4).unwrap(), '-');
226        assert_eq!(setupcode.chars().nth(9).unwrap(), '-');
227        assert_eq!(setupcode.chars().nth(14).unwrap(), '-');
228        assert_eq!(setupcode.chars().nth(19).unwrap(), '-');
229        assert_eq!(setupcode.chars().nth(24).unwrap(), '-');
230        assert_eq!(setupcode.chars().nth(29).unwrap(), '-');
231        assert_eq!(setupcode.chars().nth(34).unwrap(), '-');
232        assert_eq!(setupcode.chars().nth(39).unwrap(), '-');
233    }
234
235    #[test]
236    fn test_normalize_setup_code() {
237        let norm = normalize_setup_code("123422343234423452346234723482349234");
238        assert_eq!(norm, "1234-2234-3234-4234-5234-6234-7234-8234-9234");
239
240        let norm =
241            normalize_setup_code("\t1 2 3422343234- foo bar-- 423-45 2 34 6234723482349234      ");
242        assert_eq!(norm, "1234-2234-3234-4234-5234-6234-7234-8234-9234");
243    }
244
245    /* S_EM_SETUPFILE is a AES-256 symm. encrypted setup message created by Enigmail
246    with an "encrypted session key", see RFC 4880.  The code is in S_EM_SETUPCODE */
247    const S_EM_SETUPCODE: &str = "1742-0185-6197-1303-7016-8412-3581-4441-0597";
248    const S_EM_SETUPFILE: &str = include_str!("../../test-data/message/stress.txt");
249
250    // Autocrypt Setup Message payload "encrypted" with plaintext algorithm.
251    const S_PLAINTEXT_SETUPFILE: &str =
252        include_str!("../../test-data/message/plaintext-autocrypt-setup.txt");
253
254    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
255    async fn test_split_and_decrypt() {
256        let buf_1 = S_EM_SETUPFILE.as_bytes().to_vec();
257        let (typ, headers, base64) = split_armored_data(&buf_1).unwrap();
258        assert_eq!(typ, BlockType::Message);
259        assert!(S_EM_SETUPCODE.starts_with(headers.get(HEADER_SETUPCODE).unwrap()));
260        assert!(!headers.contains_key(HEADER_AUTOCRYPT));
261
262        assert!(!base64.is_empty());
263
264        let setup_file = S_EM_SETUPFILE.to_string();
265        let decrypted =
266            decrypt_setup_file(S_EM_SETUPCODE, std::io::Cursor::new(setup_file.as_bytes()))
267                .await
268                .unwrap();
269
270        let (typ, headers, _base64) = split_armored_data(decrypted.as_bytes()).unwrap();
271
272        assert_eq!(typ, BlockType::PrivateKey);
273        assert_eq!(headers.get(HEADER_AUTOCRYPT), Some(&"mutual".to_string()));
274        assert!(!headers.contains_key(HEADER_SETUPCODE));
275    }
276
277    /// Tests that Autocrypt Setup Message encrypted with "plaintext" algorithm cannot be
278    /// decrypted.
279    ///
280    /// According to <https://datatracker.ietf.org/doc/html/rfc4880#section-13.4>
281    /// "Implementations MUST NOT use plaintext in Symmetrically Encrypted Data packets".
282    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
283    async fn test_decrypt_plaintext_autocrypt_setup_message() {
284        let setup_file = S_PLAINTEXT_SETUPFILE.to_string();
285        let incorrect_setupcode = "0000-0000-0000-0000-0000-0000-0000-0000-0000";
286        assert!(decrypt_setup_file(
287            incorrect_setupcode,
288            std::io::Cursor::new(setup_file.as_bytes()),
289        )
290        .await
291        .is_err());
292    }
293
294    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
295    async fn test_key_transfer() -> Result<()> {
296        let alice = TestContext::new_alice().await;
297
298        alice.set_config(Config::BccSelf, Some("0")).await?;
299        let setup_code = initiate_key_transfer(&alice).await?;
300
301        // Test that sending Autocrypt Setup Message enables `bcc_self`.
302        assert_eq!(alice.get_config_bool(Config::BccSelf).await?, true);
303
304        // Get Autocrypt Setup Message.
305        let sent = alice.pop_sent_msg().await;
306
307        // Alice sets up a second device.
308        let alice2 = TestContext::new().await;
309        alice2.set_name("alice2");
310        alice2.configure_addr("alice@example.org").await;
311        alice2.recv_msg(&sent).await;
312        let msg = alice2.get_last_msg().await;
313        assert!(msg.is_setupmessage());
314        assert_eq!(
315            crate::key::load_self_secret_keyring(&alice2).await?.len(),
316            0
317        );
318
319        // Transfer the key.
320        alice2.set_config(Config::BccSelf, Some("0")).await?;
321        continue_key_transfer(&alice2, msg.id, &setup_code).await?;
322        assert_eq!(alice2.get_config_bool(Config::BccSelf).await?, true);
323        assert_eq!(
324            crate::key::load_self_secret_keyring(&alice2).await?.len(),
325            1
326        );
327
328        // Alice sends a message to self from the new device.
329        let sent = alice2.send_text(msg.chat_id, "Test").await;
330        let rcvd_msg = alice.recv_msg(&sent).await;
331        assert_eq!(rcvd_msg.get_text(), "Test");
332
333        Ok(())
334    }
335
336    /// Tests that Autocrypt Setup Messages is only clickable if it is self-sent.
337    /// This prevents Bob from tricking Alice into changing the key
338    /// by sending her an Autocrypt Setup Message as long as Alice's server
339    /// does not allow to forge the `From:` header.
340    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
341    async fn test_key_transfer_non_self_sent() -> Result<()> {
342        let mut tcm = TestContextManager::new();
343        let alice = tcm.alice().await;
344        let bob = tcm.bob().await;
345
346        let _setup_code = initiate_key_transfer(&alice).await?;
347
348        // Get Autocrypt Setup Message.
349        let sent = alice.pop_sent_msg().await;
350
351        let rcvd = bob.recv_msg(&sent).await;
352        assert!(!rcvd.is_setupmessage());
353
354        Ok(())
355    }
356
357    /// Tests reception of Autocrypt Setup Message from K-9 6.802.
358    ///
359    /// Unlike Autocrypt Setup Message sent by Delta Chat,
360    /// this message does not contain `Autocrypt-Prefer-Encrypt` header.
361    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
362    async fn test_key_transfer_k_9() -> Result<()> {
363        let t = &TestContext::new().await;
364        t.configure_addr("autocrypt@nine.testrun.org").await;
365
366        let raw = include_bytes!("../../test-data/message/k-9-autocrypt-setup-message.eml");
367        let received = receive_imf(t, raw, false).await?.unwrap();
368
369        let setup_code = "0655-9868-8252-5455-4232-5158-1237-5333-2638";
370        continue_key_transfer(t, *received.msg_ids.last().unwrap(), setup_code).await?;
371
372        Ok(())
373    }
374}
deltachat/imex/key_transfer.rs

deltachat/imex/
key_transfer.rs
