_platform: Add check_sandbox_config() method

3 files changed, 26 insertions, 1 deletions

diff --git a/buildstream/_platform/linux.py b/buildstream/_platform/linux.py
index a5fd0d687..3e31b69c8 100644
--- a/buildstream/_platform/linux.py
+++ b/buildstream/_platform/linux.py
@@ -17,6 +17,7 @@
 #  Authors:
 #        Tristan Maat <tristan.maat@codethink.co.uk>
 
+import os
 import subprocess
 
 from .. import _site
@@ -34,6 +35,9 @@ class Linux(Platform):
 
         super().__init__(context)
 
+        self._uid = os.geteuid()
+        self._gid = os.getegid()
+
         self._die_with_parent_available = _site.check_bwrap_version(0, 1, 8)
         self._user_ns_available = self._check_user_ns_available(context)
         self._artifact_cache = CASCache(context, enable_push=self._user_ns_available)
@@ -48,6 +52,15 @@ class Linux(Platform):
         kwargs['die_with_parent_available'] = self._die_with_parent_available
         return SandboxBwrap(*args, **kwargs)
 
+    def check_sandbox_config(self, config):
+        if self._user_ns_available:
+            # User namespace support allows arbitrary build UID/GID settings.
+            return True
+        else:
+            # Without user namespace support, the UID/GID in the sandbox
+            # will match the host UID/GID.
+            return config.build_uid == self._uid and config.build_gid == self._gid
+
     ################################################
     #              Private Methods                 #
     ################################################
diff --git a/buildstream/_platform/platform.py b/buildstream/_platform/platform.py
index 8a074eb62..8dcfe95e5 100644
--- a/buildstream/_platform/platform.py
+++ b/buildstream/_platform/platform.py
@@ -92,3 +92,7 @@ class Platform():
     def create_sandbox(self, *args, **kwargs):
         raise ImplError("Platform {platform} does not implement create_sandbox()"
                         .format(platform=type(self).__name__))
+
+    def check_sandbox_config(self, config):
+        raise ImplError("Platform {platform} does not implement check_sandbox_config()"
+                        .format(platform=type(self).__name__))
diff --git a/buildstream/_platform/unix.py b/buildstream/_platform/unix.py
index 0306a4ac5..e356fc89c 100644
--- a/buildstream/_platform/unix.py
+++ b/buildstream/_platform/unix.py
@@ -33,8 +33,11 @@ class Unix(Platform):
         super().__init__(context)
         self._artifact_cache = CASCache(context)
 
+        self._uid = os.geteuid()
+        self._gid = os.getegid()
+
         # Not necessarily 100% reliable, but we want to fail early.
-        if os.geteuid() != 0:
+        if self._uid != 0:
             raise PlatformError("Root privileges are required to run without bubblewrap.")
 
     @property
@@ -43,3 +46,8 @@ class Unix(Platform):
 
     def create_sandbox(self, *args, **kwargs):
         return SandboxChroot(*args, **kwargs)
+
+    def check_sandbox_config(self, config):
+        # With the chroot sandbox, the UID/GID in the sandbox
+        # will match the host UID/GID (typically 0/0).
+        return config.build_uid == self._uid and config.build_gid == self._gid