Use a rust build script to set linker options correctly for tests.

We need this trick because some of our Rust tests depend on our C
code, which in turn depend on other native libraries, which thereby
pulls a whole mess of our build system into "cargo test".

To solve this, we add a build script (build.rs) to set most of the
options that we want based on the contents of config.rust.  Some
options can't be set, and need to go to the linker directly: we use
a linker replacement (link_rust.sh) for these.  Both config.rust and
link_rust.sh are generated by autoconf for us.

This patch on its own should enough to make the crypto test build,
but not necessarily enough to make it pass.

2 files changed, 180 insertions, 1 deletions

diff --git a/src/rust/build.rs b/src/rust/build.rs
new file mode 100644
index 0000000000..b943aa5535
--- /dev/null
+++ b/src/rust/build.rs
@@ -0,0 +1,179 @@
+//! Build script for Rust modules in Tor.
+//!
+//! We need to use this because some of our Rust tests need to use some
+//! of our C modules, which need to link some external libraries.
+//!
+//! This script works by looking at a "config.rust" file generated by our
+//! configure script, and then building a set of options for cargo to pass to
+//! the compiler.
+
+use std::collections::HashMap;
+use std::env;
+use std::fs::File;
+use std::io::prelude::*;
+use std::io;
+use std::path::PathBuf;
+
+/// Wrapper around a key-value map.
+struct Config(
+    HashMap<String,String>
+);
+
+/// Locate a config.rust file generated by autoconf, starting in the OUT_DIR
+/// location provided by cargo and recursing up the directory tree.  Note that
+/// we need to look in the OUT_DIR, since autoconf will place generated files
+/// in the build directory.
+fn find_cfg() -> io::Result<String> {
+    let mut path = PathBuf::from(env::var("OUT_DIR").unwrap());
+    loop {
+        path.push("config.rust");
+        if path.exists() {
+            return Ok(path.to_str().unwrap().to_owned());
+        }
+        path.pop(); // remove config.rust
+        if ! path.pop() { // can't remove last part of directory
+            return Err(io::Error::new(io::ErrorKind::NotFound,
+                                      "No config.rust"));
+        }
+    }
+}
+
+impl Config {
+    /// Find the config.rust file and try to parse it.
+    ///
+    /// The file format is a series of lines of the form KEY=VAL, with
+    /// any blank lines and lines starting with # ignored.
+    fn load() -> io::Result<Config> {
+        let path = find_cfg()?;
+        let f = File::open(&path)?;
+        let reader = io::BufReader::new(f);
+        let mut map = HashMap::new();
+        for line in reader.lines() {
+            let s = line?;
+            if s.trim().starts_with("#") || s.trim() == "" {
+                continue;
+            }
+            let idx = match s.find("=") {
+                None => {
+                    return Err(io::Error::new(io::ErrorKind::InvalidData,
+                                              "missing ="));
+                },
+                Some(x) => x
+            };
+            let (var,eq_val) = s.split_at(idx);
+            let val = &eq_val[1..];
+            map.insert(var.to_owned(), val.to_owned());
+        }
+        Ok(Config(map))
+    }
+
+    /// Return a reference to the value whose key is 'key'.
+    ///
+    /// Panics if 'key' is not found in the configuration.
+    fn get(&self, key : &str) -> &str {
+        self.0.get(key).unwrap()
+    }
+
+    /// Add a dependency on a static C library that is part of Tor, by name.
+    fn component(&self, s : &str) {
+        println!("cargo:rustc-link-lib=static={}", s);
+    }
+
+    /// Add a dependency on a native library that is not part of Tor, by name.
+    fn dependency(&self, s : &str) {
+        println!("cargo:rustc-link-lib={}", s);
+    }
+
+    /// Add a link path, relative to Tor's build directory.
+    fn link_relpath(&self, s : &str) {
+        let builddir = self.get("BUILDDIR");
+        println!("cargo:rustc-link-search=native={}/{}", builddir, s);
+    }
+
+    /// Add an absolute link path.
+    fn link_path(&self, s : &str) {
+        println!("cargo:rustc-link-search=native={}", s);
+    }
+
+    /// Parse the CFLAGS in s, looking for -l and -L items, and adding
+    /// rust configuration as appropriate.
+    fn from_cflags(&self, s : &str) {
+        let mut next_is_lib = false;
+        let mut next_is_path = false;
+        for ent in self.get(s).split_whitespace() {
+            if next_is_lib {
+                self.dependency(ent);
+                next_is_lib = false;
+            } else if next_is_path {
+                self.link_path(ent);
+                next_is_path = false;
+            } else if ent == "-l" {
+                next_is_lib = true;
+            } else if ent == "-L" {
+                next_is_path = true;
+            } else if ent.starts_with("-L") {
+                self.link_path(&ent[2..]);
+            } else if ent.starts_with("-l") {
+                self.dependency(&ent[2..]);
+            }
+        }
+    }
+}
+
+pub fn main() {
+    let cfg = Config::load().unwrap();
+    let package = env::var("CARGO_PKG_NAME").unwrap();
+
+    match package.as_ref() {
+        "crypto" => {
+            // Right now, I'm having a separate configuration for each Rust
+            // package, since I'm hoping we can trim them down.  Once we have a
+            // second Rust package that needs to use this build script, let's
+            // extract some of this stuff into a module.
+            //
+            // This is a ridiculous amount of code to be pulling in just
+            // to test our crypto library: modularity would be our
+            // friend here.
+            cfg.from_cflags("TOR_LDFLAGS_zlib");
+            cfg.from_cflags("TOR_LDFLAGS_openssl");
+            cfg.from_cflags("TOR_LDFLAGS_libevent");
+
+            cfg.link_relpath("src/common");
+            cfg.link_relpath("src/ext/keccak-tiny");
+            cfg.link_relpath("src/ext/keccak-tiny");
+            cfg.link_relpath("src/ext/ed25519/ref10");
+            cfg.link_relpath("src/ext/ed25519/donna");
+            cfg.link_relpath("src/trunnel");
+
+            // Note that we can't pull in "libtor-testing", or else we
+            // will have dependencies on all the other rust packages that
+            // tor uses.  We must be careful with factoring and dependencies
+            // moving forward!
+            cfg.component("or-crypto-testing");
+            cfg.component("or-ctime-testing");
+            cfg.component("or-testing");
+            cfg.component("or-event-testing");
+            cfg.component("or-ctime-testing");
+            cfg.component("curve25519_donna");
+            cfg.component("keccak-tiny");
+            cfg.component("ed25519_ref10");
+            cfg.component("ed25519_donna");
+            cfg.component("or-trunnel-testing");
+
+            cfg.from_cflags("TOR_ZLIB_LIBS");
+            cfg.from_cflags("TOR_LIB_MATH");
+            cfg.from_cflags("TOR_OPENSSL_LIBS");
+            cfg.from_cflags("TOR_LIBEVENT_LIBS");
+            cfg.from_cflags("TOR_LIB_WS32");
+            cfg.from_cflags("TOR_LIB_GDI");
+            cfg.from_cflags("TOR_LIB_USERENV");
+            cfg.from_cflags("CURVE25519_LIBS");
+            cfg.from_cflags("TOR_LZMA_LIBS");
+            cfg.from_cflags("TOR_ZSTD_LIBS");
+            cfg.from_cflags("LIBS");
+        },
+        _ => {
+            panic!("No configuration in build.rs for package {}", package);
+        }
+    }
+}
diff --git a/src/rust/crypto/Cargo.toml b/src/rust/crypto/Cargo.toml
index c0c5e7bf93..9d302ee3ba 100644
--- a/src/rust/crypto/Cargo.toml
+++ b/src/rust/crypto/Cargo.toml
@@ -4,6 +4,7 @@ authors = ["The Tor Project",
 name = "crypto"
 version = "0.0.1"
 publish = false
+build = "../build.rs"
 
 [lib]
 name = "crypto"
@@ -26,4 +27,3 @@ rand_core = { version = "=0.2.0-pre.0", default-features = false }
 
 [features]
 testing = ["tor_log/testing"]
-