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 parking_lot::RwLock;
100    use std::collections::HashMap;
101
102    fn func_with_policy(name: &str, policy: Option<&str>) -> LambdaFunction {
103        LambdaFunction {
104            function_name: name.to_string(),
105            function_arn: format!("arn:aws:lambda:us-east-1:123456789012:function:{name}"),
106            runtime: "python3.12".to_string(),
107            role: "arn:aws:iam::123456789012:role/r".to_string(),
108            handler: "index.handler".to_string(),
109            description: String::new(),
110            timeout: 3,
111            memory_size: 128,
112            code_sha256: String::new(),
113            code_size: 0,
114            version: "$LATEST".to_string(),
115            last_modified: Utc::now(),
116            tags: HashMap::new(),
117            environment: HashMap::new(),
118            architectures: Vec::new(),
119            package_type: "Zip".to_string(),
120            code_zip: None,
121            image_uri: None,
122            policy: policy.map(str::to_string),
123        }
124    }
125
126    fn state_with(func: LambdaFunction) -> SharedLambdaState {
127        let mut mas: fakecloud_core::multi_account::MultiAccountState<LambdaState> =
128            fakecloud_core::multi_account::MultiAccountState::new("123456789012", "us-east-1", "");
129        mas.get_or_create("123456789012")
130            .functions
131            .insert(func.function_name.clone(), func);
132        Arc::new(RwLock::new(mas))
133    }
134
135    #[test]
136    fn parse_function_name_accepts_valid_arn() {
137        assert_eq!(
138            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:my-fn"),
139            Some("my-fn")
140        );
141    }
142
143    #[test]
144    fn parse_function_name_accepts_qualified_arn() {
145        // Qualified ARN (version / alias) — function name is still
146        // segment 4, qualifier follows as segment 5 and we drop it.
147        assert_eq!(
148            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:my-fn:PROD"),
149            Some("my-fn")
150        );
151        assert_eq!(
152            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:my-fn:7"),
153            Some("my-fn")
154        );
155    }
156
157    #[test]
158    fn parse_function_name_rejects_malformed() {
159        assert_eq!(parse_function_name(""), None);
160        assert_eq!(parse_function_name("not-an-arn"), None);
161        assert_eq!(parse_function_name("arn:aws:lambda:"), None);
162        assert_eq!(parse_function_name("arn:aws:lambda:us-east-1"), None);
163        assert_eq!(
164            parse_function_name("arn:aws:lambda:us-east-1:123456789012"),
165            None
166        );
167        // Event source mapping ARN — wrong resource type.
168        assert_eq!(
169            parse_function_name("arn:aws:lambda:us-east-1:123456789012:event-source-mapping:uuid"),
170            None
171        );
172        // Blank region or account.
173        assert_eq!(
174            parse_function_name("arn:aws:lambda::123456789012:function:f"),
175            None
176        );
177        assert_eq!(
178            parse_function_name("arn:aws:lambda:us-east-1::function:f"),
179            None
180        );
181        // Blank function name.
182        assert_eq!(
183            parse_function_name("arn:aws:lambda:us-east-1:123456789012:function:"),
184            None
185        );
186        // S3-shaped ARN.
187        assert_eq!(parse_function_name("arn:aws:s3:::my-bucket"), None);
188    }
189
190    #[test]
191    fn returns_stored_policy_for_lambda_arn() {
192        let doc = r#"{"Version":"2012-10-17","Statement":[]}"#;
193        let state = state_with(func_with_policy("my-fn", Some(doc)));
194        let provider = LambdaResourcePolicyProvider::new(state);
195        assert_eq!(
196            provider.resource_policy(
197                "lambda",
198                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
199            ),
200            Some(doc.to_string())
201        );
202    }
203
204    #[test]
205    fn qualified_arn_resolves_to_unqualified_function_policy() {
206        // Resource policies live on the function, not on specific
207        // version aliases. A qualified ARN must still resolve to the
208        // same stored document.
209        let doc = r#"{"Statement":[]}"#;
210        let state = state_with(func_with_policy("my-fn", Some(doc)));
211        let provider = LambdaResourcePolicyProvider::new(state);
212        assert_eq!(
213            provider.resource_policy(
214                "lambda",
215                "arn:aws:lambda:us-east-1:123456789012:function:my-fn:PROD"
216            ),
217            Some(doc.to_string())
218        );
219    }
220
221    #[test]
222    fn returns_none_when_function_has_no_policy() {
223        let state = state_with(func_with_policy("my-fn", None));
224        let provider = LambdaResourcePolicyProvider::new(state);
225        assert_eq!(
226            provider.resource_policy(
227                "lambda",
228                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
229            ),
230            None
231        );
232    }
233
234    #[test]
235    fn returns_none_when_function_missing() {
236        let state = state_with(func_with_policy("other", Some("{}")));
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"
242            ),
243            None
244        );
245    }
246
247    #[test]
248    fn returns_none_for_non_lambda_service_prefix() {
249        let state = state_with(func_with_policy("my-fn", Some("{}")));
250        let provider = LambdaResourcePolicyProvider::new(state);
251        assert_eq!(
252            provider.resource_policy("s3", "arn:aws:lambda:us-east-1:123456789012:function:my-fn"),
253            None
254        );
255        assert_eq!(
256            provider.resource_policy(
257                "sns",
258                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
259            ),
260            None
261        );
262    }
263
264    #[test]
265    fn service_prefix_match_is_case_insensitive() {
266        let state = state_with(func_with_policy("my-fn", Some("{}")));
267        let provider = LambdaResourcePolicyProvider::new(state);
268        assert!(provider
269            .resource_policy(
270                "LAMBDA",
271                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
272            )
273            .is_some());
274    }
275
276    #[test]
277    fn shared_constructor_wraps_in_arc() {
278        let state = state_with(func_with_policy("my-fn", Some("doc")));
279        let arc = LambdaResourcePolicyProvider::shared(state);
280        assert_eq!(
281            arc.resource_policy(
282                "lambda",
283                "arn:aws:lambda:us-east-1:123456789012:function:my-fn"
284            )
285            .as_deref(),
286            Some("doc")
287        );
288    }
289}
fakecloud_lambda/resource_policy.rs

fakecloud_lambda/
resource_policy.rs
