Add script to generate rustc --remap-path-prefix

This is needed for reproducible builds. The script  gets
the file paths to the user's Cargo and Rustup home dirs, as well as the
path to the Mullvad app source dir. These paths are then remapped to
fixed values which is needed to make the build reproducible.

3 files changed, 38 insertions, 8 deletions

diff --git a/android/app/build.gradle.kts b/android/app/build.gradle.kts
index 26db17f1bb..5bd78f7906 100644
--- a/android/app/build.gradle.kts
+++ b/android/app/build.gradle.kts
@@ -291,6 +291,11 @@ cargo {
             add("--locked")
         }
     }
+    exec = { spec, _ ->
+        val remaps = generateRemapArguments()
+        println("rustc path prefix remaps: $remaps")
+        spec.environment("RUSTFLAGS", remaps)
+    }
 }
 
 tasks.register<Exec>("generateRelayList") {
diff --git a/android/buildSrc/src/main/kotlin/Utils.kt b/android/buildSrc/src/main/kotlin/Utils.kt
index ffea7ce51f..5c70b6f290 100644
--- a/android/buildSrc/src/main/kotlin/Utils.kt
+++ b/android/buildSrc/src/main/kotlin/Utils.kt
@@ -1,7 +1,5 @@
-import java.io.ByteArrayOutputStream
 import java.util.*
 import org.gradle.api.Project
-import org.gradle.process.ExecSpec
 
 fun Project.generateVersionCode(localProperties: Properties): Int {
     return localProperties.getProperty("OVERRIDE_VERSION_CODE")?.toIntOrNull()
@@ -12,12 +10,24 @@ fun Project.generateVersionName(localProperties: Properties): String {
     return localProperties.getProperty("OVERRIDE_VERSION_NAME") ?: execVersionNameCargoCommand()
 }
 
+fun Project.generateRemapArguments(): String {
+    val script = "${projectDir.parent}/../building/rustc-remap-path-prefix.sh"
+    return providers.exec { commandLine(script) }.standardOutput.asText.get().trim()
+}
+
 private fun Project.execVersionCodeCargoCommand() =
-    providers.exec {
-        commandLine("cargo", "run", "-q", "--bin", "mullvad-version", "versionCode")
-    }.standardOutput.asText.get().trim().toInt()
+    providers
+        .exec { commandLine("cargo", "run", "-q", "--bin", "mullvad-version", "versionCode") }
+        .standardOutput
+        .asText
+        .get()
+        .trim()
+        .toInt()
 
 private fun Project.execVersionNameCargoCommand() =
-    providers.exec {
-        commandLine("cargo", "run", "-q", "--bin", "mullvad-version", "versionName")
-    }.standardOutput.asText.get().trim()
+    providers
+        .exec { commandLine("cargo", "run", "-q", "--bin", "mullvad-version", "versionName") }
+        .standardOutput
+        .asText
+        .get()
+        .trim()
diff --git a/building/rustc-remap-path-prefix.sh b/building/rustc-remap-path-prefix.sh
new file mode 100755
index 0000000000..0531d206e7
--- /dev/null
+++ b/building/rustc-remap-path-prefix.sh
@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+
+# Returns the rustc `--remap-path-prefix` flags needed to replace file paths
+# that gets put in the build artifacts with fixed values in order to make
+# the build reproducible across different machines.
+
+set -eu
+
+SOURCE_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && cd .. && pwd )"
+CARGO_HOME_PATH=${CARGO_HOME:-$HOME/.cargo}
+RUSTUP_HOME_PATH=${RUSTUP_HOME:-$HOME/.rustup}
+
+echo "--remap-path-prefix $CARGO_HOME_PATH=/CARGO_HOME \
+--remap-path-prefix $RUSTUP_HOME_PATH=/RUSTUP_HOME \
+--remap-path-prefix $SOURCE_DIR=/SOURCE_DIR"