fakecloud_lambda/
resource_policy.rs

1//! Lambda implementation of [`ResourcePolicyProvider`].
2//!
3//! Lambda persists function resource policies as raw JSON in
4//! [`crate::state::LambdaFunction::policy`]. Both `AddPermission` and
5//! `RemovePermission` write through that field, seeding a canonical
6//! `{"Version":"2012-10-17","Statement":[...]}` document so the
7//! existing cross-service evaluator path reads it without a
8//! Lambda-specific fork. This file is the read-side bridge into the
9//! `fakecloud-core::auth::ResourcePolicyProvider` trait.
10//!
11//! Mirrors [`fakecloud_sns::resource_policy::SnsResourcePolicyProvider`]
12//! and [`fakecloud_s3::resource_policy::S3ResourcePolicyProvider`]:
13//! single-service gate, ARN parsing, state lookup, return `None` for
14//! anything not owned here so composition is safe.
15
16use std::sync::Arc;
17
18use fakecloud_core::auth::ResourcePolicyProvider;
19
20use crate::state::SharedLambdaState;
21
22/// Concrete [`ResourcePolicyProvider`] backed by the in-memory
23/// [`crate::state::LambdaState`]. Server bootstrap clone-shares it via
24/// [`fakecloud_core::auth::MultiResourcePolicyProvider`] alongside the
25/// S3 and SNS providers.
26pub struct LambdaResourcePolicyProvider {
27    state: SharedLambdaState,
28}
29
30impl LambdaResourcePolicyProvider {
31    pub fn new(state: SharedLambdaState) -> Self {
32        Self { state }
33    }
34
35    /// Convenience constructor returning an
36    /// `Arc<dyn ResourcePolicyProvider>` so bootstrap can push it
37    /// directly into a `MultiResourcePolicyProvider`.
38    pub fn shared(state: SharedLambdaState) -> Arc<dyn ResourcePolicyProvider> {
39        Arc::new(Self::new(state))
40    }
41}
42
43impl ResourcePolicyProvider for LambdaResourcePolicyProvider {
44    fn resource_policy(&self, service: &str, resource_arn: &str) -> Option<String> {
45        if !service.eq_ignore_ascii_case("lambda") {
46            return None;
47        }
48        let function_name = parse_function_name(resource_arn)?;
49        // Extract account ID from ARN: arn:aws:lambda:REGION:ACCOUNT:function:NAME
50        let account_id = resource_arn.split(':').nth(4).unwrap_or("").to_string();
51        let accounts = self.state.read();
52        let state = accounts.get(&account_id)?;
53        state
54            .functions
55            .get(function_name)
56            .and_then(|f| f.policy.clone())
57    }
58}
59
60/// Extract the function name from a Lambda ARN of the form
61/// `arn:aws:lambda:REGION:ACCOUNT:function:NAME`. Qualified ARNs
62/// (`function:NAME:VERSION` or `function:NAME:ALIAS`) keep the bare
63/// function name — `LambdaState::functions` is keyed by unqualified
64/// name and resource policies are attached at the function level.
65///
66/// Returns `None` for anything that isn't a fully-qualified function
67/// ARN so the caller short-circuits to "no policy" rather than
68/// looking up stray map keys.
69fn parse_function_name(arn: &str) -> Option<&str> {
70    let rest = arn.strip_prefix("arn:aws:lambda:")?;
71    // arn:aws:lambda:REGION:ACCOUNT:function:NAME[:QUALIFIER]
72    // After the prefix: REGION:ACCOUNT:function:NAME[:QUALIFIER]
73    let parts: Vec<&str> = rest.split(':').collect();
74    // Expect at least 4 segments: region, account, "function", name.
75    if parts.len() < 4 {
76        return None;
77    }
78    let region = parts[0];
79    let account = parts[1];
80    let resource_type = parts[2];
81    let name = parts[3];
82    if region.is_empty() || account.is_empty() {
83        return None;
84    }
85    if resource_type != "function" {
86        return None;
87    }
88    if name.is_empty() {
89        return None;
90    }
91    Some(name)
92}
93
94#[cfg(test)]
95mod tests {
96    use super::*;
97    use crate::state::{LambdaFunction, LambdaState};
98    use chrono::Utc;
99    use fakecloud_aws::arn::Arn;
100    use parking_lot::RwLock;
101    use std::collections::BTreeMap;
102
103    fn func_with_policy(name: &str, policy: Option<&str>) -> LambdaFunction {
104        LambdaFunction {
105            function_name: name.to_string(),
106            function_arn: Arn::new(
107                "lambda",
108                "us-east-1",
109                "123456789012",
110                &format!("function:{name}"),
111            )
112            .to_string(),
113            runtime: "python3.12".to_string(),
114            role: "arn:aws:iam::123456789012:role/r".to_string(),
115            handler: "index.handler".to_string(),
116            description: String::new(),
117            timeout: 3,
118            memory_size: 128,
119            code_sha256: String::new(),
120            code_size: 0,
121            version: "$LATEST".to_string(),
122            last_modified: Utc::now(),
123            tags: BTreeMap::new(),
124            environment: BTreeMap::new(),
125            architectures: Vec::new(),
126            package_type: "Zip".to_string(),
127            code_zip: None,
128            image_uri: None,
129            policy: policy.map(str::to_string),
130            layers: Vec::new(),
131            revision_id: "test-rev".to_string(),
132            tracing_mode: None,
133            kms_key_arn: None,
134            ephemeral_storage_size: None,
135            vpc_config: None,
136            snap_start: None,
137            dead_letter_config_arn: None,
138            file_system_configs: Vec::new(),
139            logging_config: None,
140            image_config: None,
141            signing_profile_version_arn: None,
142            signing_job_arn: None,
143            runtime_version_config: None,
144            master_arn: None,
145            state_reason: None,
146            state_reason_code: None,
147            last_update_status_reason: None,
148            last_update_status_reason_code: None,
149        }
150    }
151
152    fn state_with(func: LambdaFunction) -> SharedLambdaState {
153        let mut mas: fakecloud_core::multi_account::MultiAccountState<LambdaState> =
154            fakecloud_core::multi_account::MultiAccountState::new("123456789012", "us-east-1", "");
155        mas.get_or_create("123456789012")
156            .functions
157            .insert(func.function_name.clone(), func);
158        Arc::new(RwLock::new(mas))
159    }
160
161    #[test]
162    fn parse_function_name_accepts_valid_arn() {
163        assert_eq!(
164            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:my-fn"),
165            Some("my-fn")
166        );
167    }
168
169    #[test]
170    fn parse_function_name_accepts_qualified_arn() {
171        // Qualified ARN (version / alias) — function name is still
172        // segment 4, qualifier follows as segment 5 and we drop it.
173        assert_eq!(
174            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:my-fn:PROD"),
175            Some("my-fn")
176        );
177        assert_eq!(
178            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:my-fn:7"),
179            Some("my-fn")
180        );
181    }
182
183    #[test]
184    fn parse_function_name_rejects_malformed() {
185        assert_eq!(parse_function_name(""), None);
186        assert_eq!(parse_function_name("not-an-arn"), None);
187        assert_eq!(parse_function_name("arn:aws:lambda:"), None);
188        assert_eq!(parse_function_name("arn:aws:lambda:us-east-1"), None);
189        assert_eq!(
190            parse_function_name("arn:aws:lambda:us-east-1:123456789012"),
191            None
192        );
193        // Event source mapping ARN — wrong resource type.
194        assert_eq!(
195            parse_function_name("arn:aws:lambda:us-east-1:123456789012:event-source-mapping:uuid"),
196            None
197        );
198        // Blank region or account.
199        assert_eq!(
200            parse_function_name("arn:aws:lambda::123456789012:function:f"),
201            None
202        );
203        assert_eq!(
204            parse_function_name("arn:aws:lambda:us-east-1::function:f"),
205            None
206        );
207        // Blank function name.
208        assert_eq!(
209            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:"),
210            None
211        );
212        // S3-shaped ARN.
213        assert_eq!(parse_function_name("arn:aws:s3:::my-bucket"), None);
214    }
215
216    #[test]
217    fn returns_stored_policy_for_lambda_arn() {
218        let doc = r#"{"Version":"2012-10-17","Statement":[]}"#;
219        let state = state_with(func_with_policy("my-fn", Some(doc)));
220        let provider = LambdaResourcePolicyProvider::new(state);
221        assert_eq!(
222            provider.resource_policy(
223                "lambda",
224                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
225            ),
226            Some(doc.to_string())
227        );
228    }
229
230    #[test]
231    fn qualified_arn_resolves_to_unqualified_function_policy() {
232        // Resource policies live on the function, not on specific
233        // version aliases. A qualified ARN must still resolve to the
234        // same stored document.
235        let doc = r#"{"Statement":[]}"#;
236        let state = state_with(func_with_policy("my-fn", Some(doc)));
237        let provider = LambdaResourcePolicyProvider::new(state);
238        assert_eq!(
239            provider.resource_policy(
240                "lambda",
241                "arn:aws:lambda:us-east-1:123456789012:function:my-fn:PROD"
242            ),
243            Some(doc.to_string())
244        );
245    }
246
247    #[test]
248    fn returns_none_when_function_has_no_policy() {
249        let state = state_with(func_with_policy("my-fn", None));
250        let provider = LambdaResourcePolicyProvider::new(state);
251        assert_eq!(
252            provider.resource_policy(
253                "lambda",
254                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
255            ),
256            None
257        );
258    }
259
260    #[test]
261    fn returns_none_when_function_missing() {
262        let state = state_with(func_with_policy("other", Some("{}")));
263        let provider = LambdaResourcePolicyProvider::new(state);
264        assert_eq!(
265            provider.resource_policy(
266                "lambda",
267                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
268            ),
269            None
270        );
271    }
272
273    #[test]
274    fn returns_none_for_non_lambda_service_prefix() {
275        let state = state_with(func_with_policy("my-fn", Some("{}")));
276        let provider = LambdaResourcePolicyProvider::new(state);
277        assert_eq!(
278            provider.resource_policy("s3", "arn:aws:lambda:us-east-1:123456789012:function:my-fn"),
279            None
280        );
281        assert_eq!(
282            provider.resource_policy(
283                "sns",
284                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
285            ),
286            None
287        );
288    }
289
290    #[test]
291    fn service_prefix_match_is_case_insensitive() {
292        let state = state_with(func_with_policy("my-fn", Some("{}")));
293        let provider = LambdaResourcePolicyProvider::new(state);
294        assert!(provider
295            .resource_policy(
296                "LAMBDA",
297                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
298            )
299            .is_some());
300    }
301
302    #[test]
303    fn shared_constructor_wraps_in_arc() {
304        let state = state_with(func_with_policy("my-fn", Some("doc")));
305        let arc = LambdaResourcePolicyProvider::shared(state);
306        assert_eq!(
307            arc.resource_policy(
308                "lambda",
309                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
310            )
311            .as_deref(),
312            Some("doc")
313        );
314    }
315}
fakecloud_lambda/resource_policy.rs

fakecloud_lambda/
resource_policy.rs
