librespot_core/
cdn_url.rs

1use std::ops::{Deref, DerefMut};
2
3use protobuf::Message;
4use thiserror::Error;
5use time::Duration;
6use url::Url;
7
8use super::{date::Date, Error, FileId, Session};
9
10use librespot_protocol as protocol;
11use protocol::storage_resolve::storage_resolve_response::Result as StorageResolveResponse_Result;
12use protocol::storage_resolve::StorageResolveResponse as CdnUrlMessage;
13
14#[derive(Debug, Clone)]
15pub struct MaybeExpiringUrl(pub String, pub Option<Date>);
16
17const CDN_URL_EXPIRY_MARGIN: Duration = Duration::seconds(5 * 60);
18
19#[derive(Debug, Clone)]
20pub struct MaybeExpiringUrls(pub Vec<MaybeExpiringUrl>);
21
22impl Deref for MaybeExpiringUrls {
23    type Target = Vec<MaybeExpiringUrl>;
24    fn deref(&self) -> &Self::Target {
25        &self.0
26    }
27}
28
29impl DerefMut for MaybeExpiringUrls {
30    fn deref_mut(&mut self) -> &mut Self::Target {
31        &mut self.0
32    }
33}
34
35#[derive(Debug, Error)]
36pub enum CdnUrlError {
37    #[error("all URLs expired")]
38    Expired,
39    #[error("resolved storage is not for CDN")]
40    Storage,
41    #[error("no URLs resolved")]
42    Unresolved,
43}
44
45impl From<CdnUrlError> for Error {
46    fn from(err: CdnUrlError) -> Self {
47        match err {
48            CdnUrlError::Expired => Error::deadline_exceeded(err),
49            CdnUrlError::Storage | CdnUrlError::Unresolved => Error::unavailable(err),
50        }
51    }
52}
53
54#[derive(Debug, Clone)]
55pub struct CdnUrl {
56    pub file_id: FileId,
57    urls: MaybeExpiringUrls,
58}
59
60impl CdnUrl {
61    pub fn new(file_id: FileId) -> Self {
62        Self {
63            file_id,
64            urls: MaybeExpiringUrls(Vec::new()),
65        }
66    }
67
68    pub async fn resolve_audio(&self, session: &Session) -> Result<Self, Error> {
69        let file_id = self.file_id;
70        let response = session.spclient().get_audio_storage(&file_id).await?;
71        let msg = CdnUrlMessage::parse_from_bytes(&response)?;
72        let urls = MaybeExpiringUrls::try_from(msg)?;
73
74        let cdn_url = Self { file_id, urls };
75
76        trace!("Resolved CDN storage: {:#?}", cdn_url);
77
78        Ok(cdn_url)
79    }
80
81    pub fn try_get_url(&self) -> Result<&str, Error> {
82        if self.urls.is_empty() {
83            return Err(CdnUrlError::Unresolved.into());
84        }
85
86        let now = Date::now_utc();
87        let url = self.urls.iter().find(|url| match url.1 {
88            Some(expiry) => now < expiry,
89            None => true,
90        });
91
92        if let Some(url) = url {
93            Ok(&url.0)
94        } else {
95            Err(CdnUrlError::Expired.into())
96        }
97    }
98}
99
100impl TryFrom<CdnUrlMessage> for MaybeExpiringUrls {
101    type Error = crate::Error;
102    fn try_from(msg: CdnUrlMessage) -> Result<Self, Self::Error> {
103        if !matches!(
104            msg.result.enum_value_or_default(),
105            StorageResolveResponse_Result::CDN
106        ) {
107            return Err(CdnUrlError::Storage.into());
108        }
109
110        let is_expiring = !msg.fileid.is_empty();
111
112        let result = msg
113            .cdnurl
114            .iter()
115            .map(|cdn_url| {
116                let url = Url::parse(cdn_url)?;
117                let mut expiry: Option<Date> = None;
118
119                if is_expiring {
120                    let mut expiry_str: Option<String> = None;
121                    if let Some(token) = url
122                        .query_pairs()
123                        .into_iter()
124                        .find(|(key, _value)| key == "__token__")
125                    {
126                        //"https://audio-ak-spotify-com.akamaized.net/audio/4712bc9e47f7feb4ee3450ef2bb545e1d83c3d54?__token__=exp=1688165560~hmac=4e661527574fab5793adb99cf04e1c2ce12294c71fe1d39ffbfabdcfe8ce3b41",
127                        if let Some(mut start) = token.1.find("exp=") {
128                            start += 4;
129                            if token.1.len() >= start {
130                                let slice = &token.1[start..];
131                                if let Some(end) = slice.find('~') {
132                                    // this is the only valid invariant for akamaized.net
133                                    expiry_str = Some(String::from(&slice[..end]));
134                                } else {
135                                    expiry_str = Some(String::from(slice));
136                                }
137                            }
138                        }
139                    } else if let Some(token) = url
140                        .query_pairs()
141                        .into_iter()
142                        .find(|(key, _value)| key == "Expires")
143                    {
144                        //"https://audio-gm-off.spotifycdn.com/audio/4712bc9e47f7feb4ee3450ef2bb545e1d83c3d54?Expires=1688165560~FullPath~hmac=IIZA28qptl8cuGLq15-SjHKHtLoxzpy_6r_JpAU4MfM=",
145                        if let Some(end) = token.1.find('~') {
146                            // this is the only valid invariant for spotifycdn.com
147                            let slice = &token.1[..end];
148                            expiry_str = Some(String::from(&slice[..end]));
149                        }
150                    } else if let Some(query) = url.query() {
151                        //"https://audio4-fa.scdn.co/audio/4712bc9e47f7feb4ee3450ef2bb545e1d83c3d54?1688165560_0GKSyXjLaTW1BksFOyI4J7Tf9tZDbBUNNPu9Mt4mhH4=",
152                        let mut items = query.split('_');
153                        if let Some(first) = items.next() {
154                            // this is the only valid invariant for scdn.co
155                            expiry_str = Some(String::from(first));
156                        }
157                    }
158
159                    if let Some(exp_str) = expiry_str {
160                        if let Ok(expiry_parsed) = exp_str.parse::<i64>() {
161                            if let Ok(expiry_at) = Date::from_timestamp_ms(expiry_parsed * 1_000) {
162                                let with_margin = expiry_at.saturating_sub(CDN_URL_EXPIRY_MARGIN);
163                                expiry = Some(Date::from(with_margin));
164                            }
165                        } else {
166                            warn!("Cannot parse CDN URL expiry timestamp '{exp_str}' from '{cdn_url}'");
167                        }
168                    } else {
169                        warn!("Unknown CDN URL format: {cdn_url}");
170                    }
171                }
172                Ok(MaybeExpiringUrl(cdn_url.to_owned(), expiry))
173            })
174            .collect::<Result<Vec<MaybeExpiringUrl>, Error>>()?;
175
176        Ok(Self(result))
177    }
178}
179
180#[cfg(test)]
181mod test {
182    use super::*;
183
184    #[test]
185    fn test_maybe_expiring_urls() {
186        let timestamp = 1688165560;
187        let mut msg = CdnUrlMessage::new();
188        msg.result = StorageResolveResponse_Result::CDN.into();
189        msg.cdnurl = vec![
190            format!("https://audio-ak-spotify-com.akamaized.net/audio/foo?__token__=exp={timestamp}~hmac=4e661527574fab5793adb99cf04e1c2ce12294c71fe1d39ffbfabdcfe8ce3b41"),
191            format!("https://audio-gm-off.spotifycdn.com/audio/foo?Expires={timestamp}~FullPath~hmac=IIZA28qptl8cuGLq15-SjHKHtLoxzpy_6r_JpAU4MfM="),
192            format!("https://audio4-fa.scdn.co/audio/foo?{timestamp}_0GKSyXjLaTW1BksFOyI4J7Tf9tZDbBUNNPu9Mt4mhH4="),
193            "https://audio4-fa.scdn.co/foo?baz".to_string(),
194        ];
195        msg.fileid = vec![0];
196
197        let urls = MaybeExpiringUrls::try_from(msg).expect("valid urls");
198        assert_eq!(urls.len(), 4);
199        assert!(urls[0].1.is_some());
200        assert!(urls[1].1.is_some());
201        assert!(urls[2].1.is_some());
202        assert!(urls[3].1.is_none());
203        let timestamp_margin = Duration::seconds(timestamp) - CDN_URL_EXPIRY_MARGIN;
204        assert_eq!(
205            urls[0].1.unwrap().as_timestamp_ms() as i128,
206            timestamp_margin.whole_milliseconds()
207        );
208    }
209}
librespot_core/cdn_url.rs

librespot_core/
cdn_url.rs
