netdoc: Use derive amplify::Getters for HsDesc accessors.

Closes #909.

Cargo.lock

@@ -49,6 +49,47 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "amplify"
+version = "4.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f26966af46e0d200e8bf2b7f16230997c1c3f2d141bc27ccc091c012ed527b58"
+dependencies = [
+ "amplify_derive",
+ "amplify_num",
+ "ascii",
+ "wasm-bindgen",
+]
+
+[[package]]
+name = "amplify_derive"
+version = "3.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c87df0f28e6eb1f2d355f29ba6793fa9ca643967528609608d5cbd70bd68f9d1"
+dependencies = [
+ "amplify_syn",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
+[[package]]
+name = "amplify_num"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ddce3bc63e807ea02065e8d8b702695f3d302ae4158baddff8b0ce5c73947251"
+
+[[package]]
+name = "amplify_syn"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7736fb8d473c0d83098b5bac44df6a561e20470375cd8bcae30516dc889fd62a"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "android-tzdata"
 version = "0.1.1"
@@ -288,6 +329,12 @@ dependencies = [
  "tracing-subscriber",
 ]
 
+[[package]]
+name = "ascii"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d92bec98840b8f03a5ff5413de5293bfcd8bf96467cf5452609f939ec6f5de16"
+
 [[package]]
 name = "assert-impl"
 version = "0.1.3"
@@ -4569,6 +4616,7 @@ dependencies = [
 name = "tor-netdoc"
 version = "0.8.0"
 dependencies = [
+ "amplify",
  "base64ct",
  "bitflags 2.3.1",
  "cipher",

crates/tor-netdoc/Cargo.toml

@@ -78,6 +78,7 @@ dangerous-expose-struct-fields = ["visible", "visibility", "__is_experimental"]
 __is_experimental = []
 
 [dependencies]
+amplify = { version = "4", default-features = false, features = ["derive"] }
 base64ct = { version = "1.5.1", features = ["alloc"] }
 bitflags = "2"
 cipher = { version = "0.4.1", features = ["zeroize"] }

crates/tor-netdoc/src/doc/hsdesc.rs

@@ -130,7 +130,7 @@ pub enum IntroAuthType {
 
 /// Information in an onion service descriptor about a single
 /// introduction point.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, amplify::Getters)]
 pub struct IntroPointDesc {
     /// The list of link specifiers needed to extend a circuit to the introduction point.
     ///
@@ -138,6 +138,7 @@ pub struct IntroPointDesc {
     //
     // TODO hs: perhaps we should make certain link specifiers mandatory? That
     // would make it possible for IntroPointDesc to implement CircTarget.
+    #[getter(skip)]
     link_specifiers: Vec<EncodedLinkSpec>,
 
     /// The key to be used to extend a circuit _to the introduction point_, using the
@@ -298,21 +299,11 @@ impl HsDesc {
     /// One or more introduction points used to contact the onion service.
     ///
     /// Accessor function.
-    // TODO HS derive this accessor
     //
-    // For this and others I considered the following crates:
+    // TODO: We'd like to derive this, but amplify::Getters  would give us &Vec<>,
+    // not &[].
     //
-    //  * amplify_derive, derive-getters, accessors-rs:
+    // Perhaps someday we can use derive_adhoc, or add as_ref() support?
-    //    No way to deref the Vec to [], which I think is desirable
-    //    (after all, eventually these might become Box<[]>.
-    //
-    //  * getset: Always generates methods called `get_` which isn't what we want.
-    //  * tia: Same problem.  Also strange API.
-    //  * field_accessor: Works with Strings.
-    //  * accessors: Always uses `get` prefix, underdocumented.
-    //  * structural: Seems to be something much more reflection-y.
-    //
-    // derive-adhoc would make short work of this problem.
     pub fn intro_points(&self) -> &[IntroPointDesc] {
         &self.intro_points
     }
@@ -324,41 +315,12 @@ impl IntroPointDesc {
     /// These can include public keys and network addresses.
     ///
     /// Accessor function.
-    // TODO HS derive this accessor (see above)
+    //
+    // TODO: It would be better to derive this too, but this accessor needs to
+    // return a slice; Getters can only give us a &Vec<> in this case.
     pub fn link_specifiers(&self) -> &[EncodedLinkSpec] {
         &self.link_specifiers
     }
-
-    /// The key to be used to extend a circuit _to the introduction point_, using the
-    /// ntor or ntor3 handshakes.  (`KP_ntor`)
-    ///
-    /// Accessor function.
-    // TODO HS derive this accessor (see above)
-    pub fn ipt_ntor_key(&self) -> &curve25519::PublicKey {
-        &self.ipt_ntor_key
-    }
-
-    /// The key to be used to identify the onion service at this introduction point.
-    /// (`KP_hs_ipt_sid`)
-    ///
-    /// Accessor function.
-    // TODO HS derive this accessor (see above)
-    pub fn ipt_sid_key(&self) -> &HsIntroPtSessionIdKey {
-        &self.ipt_sid_key
-    }
-
-    /// `KP_hss_ntor`, the key used to encrypt a handshake _to the onion
-    /// service_ when using this introduction point.
-    ///
-    /// The onion service uses a separate key of this type with each
-    /// introduction point as part of its strategy for preventing replay
-    /// attacks.
-    ///
-    /// Accessor function.
-    // TODO HS derive this accessor (see above)
-    pub fn svc_ntor_key(&self) -> &HsSvcNtorKey {
-        &self.svc_ntor_key
-    }
 }
 
 impl EncryptedHsDesc {