[release-1.27] Properly validate cache IDs and sources

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 # Changelog
 
+## v1.27.5 (2024-10-24)
+
+    Properly validate cache IDs and sources
+
 ## v1.27.4 (2024-03-26)
 
     [release-1.27] Bump Bump google.golang.org/protobuf to v1.33.0

changelog.txt

@@ -1,3 +1,6 @@
+- Changelog for v1.27.5 (2024-10-24)
+  * Properly validate cache IDs and sources
+
 - Changelog for v1.27.4 (2024-03-26)
   * [release-1.27] Bump Bump google.golang.org/protobuf to v1.33.0
   * [release-1.27] conformance tests: don't break on trailing zeroes

define/types.go

@@ -30,7 +30,7 @@ const (
 	Package = "buildah"
 	// Version for the Package.  Bump version in contrib/rpm/buildah.spec
 	// too.
-	Version = "1.27.4"
+	Version = "1.27.5"
 
 	// DefaultRuntime if containers.conf fails.
 	DefaultRuntime = "runc"

internal/parse/parse.go

@@ -18,6 +18,7 @@ import (
 	"github.com/containers/storage"
 	"github.com/containers/storage/pkg/idtools"
 	"github.com/containers/storage/pkg/lockfile"
+	digest "github.com/opencontainers/go-digest"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 )
 
@@ -306,7 +307,11 @@ func GetCacheMount(args []string, store storage.Store, imageMountLabel string, a
 			return newMount, lockedTargets, fmt.Errorf("no stage found with name %s", fromStage)
 		}
 		// path should be /contextDir/specified path
-		newMount.Source = filepath.Join(mountPoint, filepath.Clean(string(filepath.Separator)+newMount.Source))
+		evaluated, err := copier.Eval(mountPoint, string(filepath.Separator)+newMount.Source, copier.EvalOptions{})
+		if err != nil {
+			return newMount, nil, err
+		}
+		newMount.Source = evaluated
 	} else {
 		// we need to create cache on host if no image is being used
 
@@ -323,9 +328,13 @@ func GetCacheMount(args []string, store storage.Store, imageMountLabel string, a
 		}
 
 		if id != "" {
-			newMount.Source = filepath.Join(cacheParent, filepath.Clean(id))
+			// Don't let the user control where we place the directory.
+			dirID := digest.FromString(id).Encoded()[:16]
+			newMount.Source = filepath.Join(cacheParent, dirID)
 		} else {
-			newMount.Source = filepath.Join(cacheParent, filepath.Clean(newMount.Destination))
+			// Don't let the user control where we place the directory.
+			dirID := digest.FromString(newMount.Destination).Encoded()[:16]
+			newMount.Source = filepath.Join(cacheParent, dirID)
 		}
 		idPair := idtools.IDPair{
 			UID: uid,

tests/bud.bats

@@ -5236,3 +5236,44 @@ _EOF
   assert "$status" -eq 2 "exit code from ls"
   expect_output --substring "No such file or directory"
 }
+
+@test "build-check-cve-2024-9675" {
+  _prefetch alpine
+
+  # SELinux can successfully block this exploit.
+  if ! which selinuxenabled > /dev/null 2> /dev/null ; then
+      searg=""
+  elif selinuxenabled ; then
+      searg="--security-opt=label=disable"
+  fi
+
+  touch ${TEST_SCRATCH_DIR}/file.txt
+
+  cat > ${TEST_SCRATCH_DIR}/Containerfile <<EOF
+FROM alpine
+RUN --mount=type=cache,id=../../../../../../../../../../../$TEST_SCRATCH_DIR,target=/var/tmp \
+ls -l /var/tmp && cat /var/tmp/file.txt
+EOF
+
+  run_buildah 1 build --no-cache $searg ${TEST_SCRATCH_DIR}
+  expect_output --substring "cat: can't open '/var/tmp/file.txt': No such file or directory"
+
+  cat > ${TEST_SCRATCH_DIR}/Containerfile <<EOF
+FROM alpine
+RUN --mount=type=cache,source=../../../../../../../../../../../$TEST_SCRATCH_DIR,target=/var/tmp \
+ls -l /var/tmp && cat /var/tmp/file.txt
+EOF
+
+  run_buildah 1 build --no-cache $searg ${TEST_SCRATCH_DIR}
+  expect_output --substring "cat: can't open '/var/tmp/file.txt': No such file or directory"
+
+  mkdir ${TEST_SCRATCH_DIR}/cve20249675
+  cat > ${TEST_SCRATCH_DIR}/cve20249675/Containerfile <<EOF
+FROM alpine
+RUN --mount=type=cache,from=testbuild,source=../,target=/var/tmp \
+ls -l /var/tmp && cat /var/tmp/file.txt
+EOF
+
+  run_buildah 1 build --no-cache $searg --build-context testbuild=${TEST_SCRATCH_DIR}/cve20249675/ ${TEST_SCRATCH_DIR}/cve20249675/
+  expect_output --substring "cat: can't open '/var/tmp/file.txt': No such file or directory"
+}