Add Signal protobuf files and compile them to Rust.

It would be cleaner to yield the compiled files OUT_DIR, but that gets
ugly very fast because of
rust-lang/rust#48250.

libsignal-service/.gitignore

@@ -0,0 +1 @@
+src/proto/*.rs

libsignal-service/Cargo.toml

@@ -12,7 +12,13 @@ failure = "0.1.5"
 async-trait = "0.1.30"
 url = "2.1.1"
 thiserror = "1.0"
+serde = {version = "1.0", features=["derive"]}
+serde_json = "1.0"
+protobuf = "2.0.0"
 
 [dev-dependencies]
 structopt = "0.2.17"
 tokio = { version = "0.2", features=["macros"] }
+
+[build-dependencies]
+protoc-rust = "2.0"

libsignal-service/build.rs

@@ -0,0 +1,37 @@
+use std::path::Path;
+
+use protoc_rust::Customize;
+
+fn main() {
+    let protobuf = Path::new(env!("CARGO_MANIFEST_DIR")).join("protobuf");
+
+    let input: Vec<_> = protobuf
+        .read_dir()
+        .expect("protobuf directory")
+        .filter_map(|entry| {
+            let entry = entry.expect("readable protobuf directory");
+            let path = entry.path();
+            if Some("proto")
+                == path.extension().and_then(std::ffi::OsStr::to_str)
+            {
+                assert!(path.is_file());
+                println!("cargo:rerun-if-changed={}", path.to_str().unwrap());
+                Some(path.to_str().unwrap().to_string())
+            } else {
+                None
+            }
+        })
+        .collect();
+
+    let input: Vec<&str> = input.iter().map(String::as_ref).collect();
+
+    protoc_rust::run(protoc_rust::Args {
+        out_dir: "src/proto",
+        input: &input,
+        includes: &[protobuf.to_str().unwrap()],
+        customize: Customize {
+            ..Default::default()
+        },
+    })
+    .expect("protoc");
+}

libsignal-service/protobuf/Provisioning.proto

@@ -0,0 +1,36 @@
+/**
+ * Copyright (C) 2014-2016 Open Whisper Systems
+ *
+ * Licensed according to the LICENSE file in this repository.
+ */
+syntax = "proto2";
+
+package signalservice;
+
+option java_package         = "org.whispersystems.signalservice.internal.push";
+option java_outer_classname = "ProvisioningProtos";
+
+message ProvisionEnvelope {
+  optional bytes publicKey = 1;
+  optional bytes body      = 2; // Encrypted ProvisionMessage
+}
+
+message ProvisionMessage {
+  optional bytes  identityKeyPublic   = 1;
+  optional bytes  identityKeyPrivate  = 2;
+  optional string number              = 3;
+  optional string uuid                = 8;
+  optional string provisioningCode    = 4;
+  optional string userAgent           = 5;
+  optional bytes  profileKey          = 6;
+  optional bool   readReceipts        = 7;
+  optional uint32 provisioningVersion = 9;
+}
+
+enum ProvisioningVersion {
+  option allow_alias = true;
+
+  INITIAL         = 0;
+  TABLET_SUPPORT  = 1;
+  CURRENT         = 1;
+}