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.
mullvad · Jan 23, 2025 · 1a58706 · 1a58706
1 parent dfa2979
commit 1a58706
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Showing 3 changed files with 38 additions and 8 deletions.
diff --git 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
@@ -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
@@ -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"