Update OTA to understand SELinux filesystem labels

Make fs_config aware of SELinux contexts, and output the context
whenever we output the UID / GID / file perms.

Pass the selinux context to the set_perm2() and set_perm2_recursive()
calls. When the OTA script fixes up filesystem permissions, it will
also fix up the SELinux context on the files.

Bug: 8985290
Change-Id: I6419b64c06309a93ac6b2f2cf9fc7f8815adeaf3

2 files changed, 76 insertions, 5 deletions

diff --git a/tools/fs_config/Android.mk b/tools/fs_config/Android.mk
index 5ef32dd34..02deabbf7 100644
--- a/tools/fs_config/Android.mk
+++ b/tools/fs_config/Android.mk
@@ -17,6 +17,7 @@ include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES := fs_config.c
 LOCAL_MODULE := fs_config
+LOCAL_STATIC_LIBRARIES := libselinux
 LOCAL_FORCE_STATIC_EXECUTABLE := true
 
 include $(BUILD_HOST_EXECUTABLE)
diff --git a/tools/fs_config/fs_config.c b/tools/fs_config/fs_config.c
index f6760cc5a..60c323800 100644
--- a/tools/fs_config/fs_config.c
+++ b/tools/fs_config/fs_config.c
@@ -15,11 +15,16 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/stat.h>
 #include <errno.h>
 #include <unistd.h>
 #include <string.h>
 
+#include <selinux/selinux.h>
+#include <selinux/label.h>
+#include <selinux/android.h>
+
 #include "private/android_filesystem_config.h"
 
 // This program takes a list of files and directories (indicated by a
@@ -29,19 +34,56 @@
 //
 // Example input:
 //
-//    system/etc/dbus.conf
-//    data/app/
+//      system/etc/dbus.conf
+//      data/app/
 //
 // Output:
 //
-//    system/etc/dbus.conf 1002 1002 440
-//    data/app 1000 1000 771
+//      system/etc/dbus.conf 1002 1002 440
+//      data/app 1000 1000 771
+//
+//   or if -S is used:
+//
+//      system/etc/dbus.conf 1002 1002 440 u:object_r:system_file:s0
+//      data/app 1000 1000 771 u:object_r:apk_data_file:s0
 //
 // Note that the output will omit the trailing slash from
 // directories.
 
+static struct selabel_handle* get_sehnd(const char* context_file) {
+  struct selinux_opt seopts[] = { { SELABEL_OPT_PATH, context_file } };
+  struct selabel_handle* sehnd = selabel_open(SELABEL_CTX_FILE, seopts, 1);
+
+  if (!sehnd) {
+    perror("error running selabel_open");
+    exit(EXIT_FAILURE);
+  }
+  return sehnd;
+}
+
+static void usage() {
+  fprintf(stderr, "Usage: fs_config [-S context_file]\n");
+}
+
 int main(int argc, char** argv) {
   char buffer[1024];
+  const char* context_file = NULL;
+  struct selabel_handle* sehnd = NULL;
+  int opt;
+  while((opt = getopt(argc, argv, "S:")) != -1) {
+    switch(opt) {
+    case 'S':
+      context_file = optarg;
+      break;
+    default:
+      usage();
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  if (context_file != NULL) {
+    sehnd = get_sehnd(context_file);
+  }
 
   while (fgets(buffer, 1023, stdin) != NULL) {
     int is_dir = 0;
@@ -64,7 +106,35 @@ int main(int argc, char** argv) {
     unsigned uid = 0, gid = 0, mode = 0;
     uint64_t capabilities;
     fs_config(buffer, is_dir, &uid, &gid, &mode, &capabilities);
-    printf("%s %d %d %o\n", buffer, uid, gid, mode);
+    printf("%s %d %d %o", buffer, uid, gid, mode);
+
+    if (sehnd != NULL) {
+      size_t buffer_strlen = strnlen(buffer, sizeof(buffer));
+      if (buffer_strlen >= sizeof(buffer)) {
+        fprintf(stderr, "non null terminated buffer, aborting\n");
+        exit(EXIT_FAILURE);
+      }
+      size_t full_name_size = buffer_strlen + 2;
+      char* full_name = (char*) malloc(full_name_size);
+      if (full_name == NULL) {
+        perror("malloc");
+        exit(EXIT_FAILURE);
+      }
+
+      full_name[0] = '/';
+      strncpy(full_name + 1, buffer, full_name_size - 1);
+      full_name[full_name_size - 1] = '\0';
+
+      char* secontext;
+      if (selabel_lookup(sehnd, &secontext, full_name, ( mode | (is_dir ? S_IFDIR : S_IFREG)))) {
+        secontext = strdup("u:object_r:unlabeled:s0");
+      }
+
+      printf(" %s", secontext);
+      free(full_name);
+      freecon(secontext);
+    }
+    printf("\n");
   }
   return 0;
 }