Extend run-as with optional --user argument.

1. Calculate AID for spawned process as (100000 * $user) + uid_from_packages.list
2. Use /data/user/$user/$packageDir as a root of a new process if $user != 0.

Change-Id: I761dfb481114bd51e5a950307fcaf403e96eef10
(cherry picked from commit da31778f3b422d9583f334273eb8d9f6aabd5d34)

3 files changed, 48 insertions, 13 deletions

diff --git a/run-as/package.c b/run-as/package.c
index 9e1f5bb..aea89e5 100644
--- a/run-as/package.c
+++ b/run-as/package.c
@@ -16,6 +16,7 @@
 */
 #include <errno.h>
 #include <fcntl.h>
+#include <stdio.h>
 #include <string.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
@@ -421,7 +422,7 @@ parse_positive_decimal(const char** pp, const char* end)
  * If the package database is corrupted, return -1 and set errno to EINVAL
  */
 int
-get_package_info(const char* pkgName, PackageInfo *info)
+get_package_info(const char* pkgName, uid_t userId, PackageInfo *info)
 {
     char*        buffer;
     size_t       buffer_len;
@@ -506,7 +507,20 @@ get_package_info(const char* pkgName, PackageInfo *info)
         if (q == p)
             goto BAD_FORMAT;
 
-        p = string_copy(info->dataDir, sizeof info->dataDir, p, q - p);
+        /* If userId == 0 (i.e. user is device owner) we can use dataDir value
+         * from packages.list, otherwise compose data directory as
+         * /data/user/$uid/$packageId
+         */
+        if (userId == 0) {
+            p = string_copy(info->dataDir, sizeof info->dataDir, p, q - p);
+        } else {
+            snprintf(info->dataDir,
+                     sizeof info->dataDir,
+                     "/data/user/%d/%s",
+                     userId,
+                     pkgName);
+            p = q;
+        }
 
         /* skip spaces */
         if (parse_spaces(&p, end) < 0)
diff --git a/run-as/package.h b/run-as/package.h
index 34603c0..eeb5913 100644
--- a/run-as/package.h
+++ b/run-as/package.h
@@ -33,9 +33,11 @@ typedef struct {
     char   seinfo[PATH_MAX];
 } PackageInfo;
 
-/* see documentation in package.c for these functiosn */
+/* see documentation in package.c for these functions */
 
-extern int  get_package_info(const char* packageName, PackageInfo*  info);
+extern int  get_package_info(const char* packageName,
+                             uid_t userId,
+                             PackageInfo*  info);
 
 extern int  check_data_path(const char* dataDir, uid_t uid);
 
diff --git a/run-as/run-as.c b/run-as/run-as.c
index 368b8f1..3f32e7d 100644
--- a/run-as/run-as.c
+++ b/run-as/run-as.c
@@ -102,13 +102,14 @@ panic(const char* format, ...)
 static void
 usage(void)
 {
-    panic("Usage:\n    " PROGNAME " <package-name> <command> [<args>]\n");
+    panic("Usage:\n    " PROGNAME " <package-name> [--user <uid>] <command> [<args>]\n");
 }
 
 int main(int argc, char **argv)
 {
     const char* pkgname;
-    int myuid, uid, gid;
+    uid_t myuid, uid, gid, userAppId = 0;
+    int commandArgvOfs = 2, userId = 0;
     PackageInfo info;
     struct __user_cap_header_struct capheader;
     struct __user_cap_data_struct capdata[2];
@@ -136,14 +137,31 @@ int main(int argc, char **argv)
         panic("Could not set capabilities: %s\n", strerror(errno));
     }
 
-    /* retrieve package information from system (does setegid) */
     pkgname = argv[1];
-    if (get_package_info(pkgname, &info) < 0) {
+
+    /* get user_id from command line if provided */
+    if ((argc >= 4) && !strcmp(argv[2], "--user")) {
+        userId = atoi(argv[3]);
+        if (userId < 0)
+            panic("Negative user id %d is provided\n", userId);
+        commandArgvOfs += 2;
+    }
+
+    /* retrieve package information from system (does setegid) */
+    if (get_package_info(pkgname, userId, &info) < 0) {
         panic("Package '%s' is unknown\n", pkgname);
     }
 
+    /* verify that user id is not too big. */
+    if ((UID_MAX - info.uid) / AID_USER < (uid_t)userId) {
+        panic("User id %d is too big\n", userId);
+    }
+
+    /* calculate user app ID. */
+    userAppId = (AID_USER * userId) + info.uid;
+
     /* reject system packages */
-    if (info.uid < AID_APP) {
+    if (userAppId < AID_APP) {
         panic("Package '%s' is not an application\n", pkgname);
     }
 
@@ -153,14 +171,14 @@ int main(int argc, char **argv)
     }
 
     /* check that the data directory path is valid */
-    if (check_data_path(info.dataDir, info.uid) < 0) {
+    if (check_data_path(info.dataDir, userAppId) < 0) {
         panic("Package '%s' has corrupt installation\n", pkgname);
     }
 
     /* Ensure that we change all real/effective/saved IDs at the
      * same time to avoid nasty surprises.
      */
-    uid = gid = info.uid;
+    uid = gid = userAppId;
     if(setresgid(gid,gid,gid) || setresuid(uid,uid,uid)) {
         panic("Permission denied\n");
     }
@@ -181,8 +199,9 @@ int main(int argc, char **argv)
     }
 
     /* User specified command for exec. */
-    if ((argc >= 3) && (execvp(argv[2], argv+2) < 0)) {
-        panic("exec failed for %s: %s\n", argv[2], strerror(errno));
+    if ((argc >= commandArgvOfs + 1) &&
+        (execvp(argv[commandArgvOfs], argv+commandArgvOfs) < 0)) {
+        panic("exec failed for %s: %s\n", argv[commandArgvOfs], strerror(errno));
     }
 
     /* Default exec shell. */