stripe_wh_verify/
lib.rs

1use hex::encode as encode_hex;
2use hmac::{Hmac, Mac, NewMac};
3use sha2::Sha256;
4type HmacSha256 = Hmac<Sha256>;
5use constant_time_eq::constant_time_eq;
6use std::collections::HashMap;
7use std::error::Error;
8use std::fmt::{Debug, Display};
9
10#[derive(Debug)]
11struct InvalidKeyValuePair;
12
13impl Display for InvalidKeyValuePair {
14    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
15        write!(f, "invalid key value pair")
16    }
17}
18impl Error for InvalidKeyValuePair {}
19
20pub(crate) fn compute_signature(payload: &str, secret: &str) -> String {
21    let mut mac = HmacSha256::new_varkey(secret.as_bytes()).expect("HMAC can take key of any size");
22    mac.update(payload.as_bytes());
23
24    let result = mac.finalize();
25    let result = result.into_bytes().as_slice().to_vec();
26
27    encode_hex(result)
28}
29
30pub(crate) fn parse_stripe_signature_header(
31    header: &str,
32) -> Result<HashMap<String, String>, Box<dyn Error>> {
33    let signature = header.trim().to_string();
34    let signature: Vec<&str> = signature.split(",").collect();
35    let signature: Vec<Vec<&str>> = signature
36        .iter()
37        .map(|pair| pair.split("=").map(|s| s.trim()).collect())
38        .collect();
39
40    let mut values: HashMap<String, String> = HashMap::new();
41
42    for pair in &signature {
43        if pair.len() != 2 {
44            return Err(Box::new(InvalidKeyValuePair));
45        }
46
47        let key = pair.first();
48        let value = pair.last();
49
50        values.insert(key.unwrap().to_string(), value.unwrap().to_string());
51    }
52
53    Ok(values)
54}
55
56/// Implements Webhook payload verification, in accordance with official Stripe docs.
57/// See [docs](https://stripe.com/docs/webhooks/signatures) for details.
58///
59/// # Errors
60///
61/// This function will return Err whenever the payload does not contain
62/// the required entries (```v1``` and ```t```).
63pub fn verify(secret: &str, header: &str, payload: &str) -> Result<bool, Box<dyn Error>> {
64    let parsed_header = parse_stripe_signature_header(header)?;
65
66    let received_timestamp = parsed_header.get("t").ok_or(InvalidKeyValuePair)?;
67    let received_signature = parsed_header.get("v1").ok_or(InvalidKeyValuePair)?;
68
69    let payload = format!("{}.{}", received_timestamp, payload);
70    let expected_signature = &compute_signature(&payload, &secret);
71
72    Ok(constant_time_eq(
73        expected_signature.as_bytes(),
74        received_signature.as_bytes(),
75    ))
76}
77
78#[cfg(test)]
79mod tests {
80    use std::time::{SystemTime, UNIX_EPOCH};
81
82    use crate::compute_signature;
83    use crate::parse_stripe_signature_header;
84    use crate::verify;
85
86    pub(crate) fn generate_test_header(payload: String) -> String {
87        let start = SystemTime::now();
88        let timestamp = start
89            .duration_since(UNIX_EPOCH)
90            .expect("time went backwards")
91            .as_secs()
92            .to_string();
93
94        let payload = format!("{}.{}", timestamp, payload);
95        let signature = compute_signature(&payload, "really secure secret");
96
97        let header = format!("t={},v1={},v0=", timestamp, signature);
98
99        return header;
100    }
101
102    #[test]
103    fn it_parses_stripe_signature_header() {
104        let stripe_signature_header = generate_test_header("sample payload".to_string());
105        dbg!(&stripe_signature_header);
106
107        let values = parse_stripe_signature_header(&stripe_signature_header).unwrap();
108
109        assert!(values.get("t").is_some());
110        assert!(values.get("v1").is_some());
111
112        assert!(verify(
113            "really secure secret",
114            &stripe_signature_header,
115            "sample payload",
116        )
117        .unwrap());
118    }
119}
stripe_wh_verify/lib.rs

stripe_wh_verify/
lib.rs
