Add INTERACT_ACROSS_USERS permission

This is a signature-level permission required in order to call
getPackagesForUid for other users/profiles. It will be granted on first
root capture start.

See #217

app/src/main/AndroidManifest.xml

@@ -11,9 +11,11 @@
     <uses-permission android:name="android.permission.WRITE_CLIPS" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" tools:ignore="ScopedStorage" />
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
-
     <uses-permission android:name="com.pcapdroid.permission.MITM" android:required="false"/>
 
+    <!-- Required with root to properly resolve UIDs cross-users/profiles. Granted via root -->
+    <uses-permission android:name="android.permission.INTERACT_ACROSS_USERS" android:protectionLevel="signature"  tools:ignore="ProtectedPermissions" />
+
     <uses-feature android:name="android.software.leanback" android:required="false" />
     <uses-feature android:name="android.hardware.touchscreen" android:required="false" />
     <uses-feature android:name="android.hardware.wifi" android:required="false" />

app/src/main/java/com/emanuelef/remote_capture/AppsResolver.java

@@ -112,7 +112,8 @@ public class AppsResolver {
         try {
             packages = mPm.getPackagesForUid(uid);
         } catch (SecurityException e) {
-            // this is a bug in some devices https://github.com/AdguardTeam/AdguardForAndroid/issues/173
+            // A SecurityException is normally raised when trying to query a package of another user/profile
+            // without holding the INTERACT_ACROSS_USERS/INTERACT_ACROSS_PROFILES permissions
             e.printStackTrace();
         }
 

app/src/main/java/com/emanuelef/remote_capture/CaptureService.java

@@ -418,6 +418,12 @@ public class CaptureService extends VpnService implements Runnable {
                 Utils.showToast(this, R.string.vpn_setup_failed);
                 return abortStart();
             }
+        } else {
+            // Root capture
+            if(checkCallingOrSelfPermission(Utils.INTERACT_ACROSS_USERS) != PackageManager.PERMISSION_GRANTED) {
+                boolean success = Utils.rootGrantPermission(Utils.INTERACT_ACROSS_USERS);
+                Utils.showToast(this, success ? R.string.permission_granted : R.string.permission_grant_fail, "INTERACT_ACROSS_USERS");
+            }
         }
 
         mWhitelist = PCAPdroid.getInstance().getMalwareWhitelist();
@@ -1224,4 +1230,5 @@ public class CaptureService extends VpnService implements Runnable {
     public static native void nativeSetFirewallEnabled(boolean enabled);
     public static native int getNumCheckedMalwareConnections();
     public static native int getNumCheckedFirewallConnections();
+    public static native int rootCmd(String prog, String args);
 }

app/src/main/java/com/emanuelef/remote_capture/Utils.java

@@ -127,6 +127,7 @@ import javax.net.ssl.HttpsURLConnection;
 
 public class Utils {
     static final String TAG = "Utils";
+    public static final String INTERACT_ACROSS_USERS = "android.permission.INTERACT_ACROSS_USERS";
     public static final int UID_UNKNOWN = -1;
     public static final int UID_NO_FILTER = -2;
     private static Boolean rootAvailable = null;
@@ -502,13 +503,13 @@ public class Utils {
         return false;
     }
 
-    public static void showToast(Context context, int id) {
-        String msg = context.getResources().getString(id);
+    public static void showToast(Context context, int id, Object... args) {
+        String msg = context.getResources().getString(id, (Object[]) args);
         Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
     }
 
-    public static void showToastLong(Context context, int id) {
-        String msg = context.getResources().getString(id);
+    public static void showToastLong(Context context, int id, Object... args) {
+        String msg = context.getResources().getString(id, (Object[]) args);
         Toast.makeText(context, msg, Toast.LENGTH_LONG).show();
     }
 
@@ -1182,4 +1183,8 @@ public class Utils {
         tv.setText(text);
         tv.setMovementMethod(LinkMovementMethod.getInstance());
     }
+
+    public static boolean rootGrantPermission(String perm) {
+        return CaptureService.rootCmd("pm", String.format("grant %s %s", BuildConfig.APPLICATION_ID, perm)) == 0;
+    }
 }

app/src/main/jni/common/utils.c

@@ -21,6 +21,8 @@
 #include <errno.h>
 #include <unistd.h>
 #include <stdarg.h>
+#include <sys/wait.h>
+#include <paths.h>
 #include "utils.h"
 
 memtrack_t memtrack = {0};
@@ -28,6 +30,9 @@ int loglevel = 0;
 const char *logtag = "pcapdroid-native";
 void (*logcallback)(int lvl, const char *msg) = NULL;
 
+// Needed for local compilation, don't remove
+extern char **environ;
+
 /* ******************************************************* */
 
 void set_log_level(int lvl) {
@@ -191,3 +196,78 @@ void hexdump(const char *buf, size_t bufsize) {
     out[idx] = '\0';
     log_d("%s", out);
 }
+
+/* ******************************************************* */
+
+int run_shell_cmd(const char *prog, const char *args, bool as_root, bool check_error) {
+    int in_p[2], out_p[2];
+    int rv = -1;
+    pid_t pid;
+
+    if((pipe(in_p) != 0) || (pipe(out_p) != 0)) {
+        log_f("pipe failed[%d]: %s", errno, strerror(errno));
+        return -1;
+    }
+
+    if((pid = fork()) == 0) {
+        // child
+        char *argp[] = {"sh", "-c", as_root ? "su" : "sh", NULL};
+
+        close(in_p[1]);
+        close(out_p[0]);
+
+        dup2(in_p[0], STDIN_FILENO);
+        dup2(out_p[1], STDOUT_FILENO);
+        dup2(out_p[1], STDERR_FILENO);
+
+        execve(_PATH_BSHELL, argp, environ);
+        fprintf(stderr, "execve failed[%d]: %s", errno, strerror(errno));
+        exit(1);
+    } else if(pid > 0) {
+        // parent
+        int out = out_p[0];
+        close(in_p[0]);
+        close(out_p[1]);
+
+        // write "su" command input
+        log_d("run_shell_cmd[%d]: %s %s", pid, prog, args);
+        write(in_p[1], prog, strlen(prog));
+        write(in_p[1], " ", 1);
+        write(in_p[1], args, strlen(args));
+        write(in_p[1], "\n", 1);
+        close(in_p[1]);
+
+        waitpid(pid, &rv, 0);
+
+        if(check_error && (rv != 0)) {
+            char buf[128];
+            struct timeval timeout = {0};
+            fd_set fds;
+
+            buf[0] = '\0';
+            FD_ZERO(&fds);
+            FD_SET(out, &fds);
+
+            select(out + 1, &fds, NULL, NULL, &timeout);
+            if (FD_ISSET(out, &fds)) {
+                int num = read(out, buf, sizeof(buf) - 1);
+                if (num > 0)
+                    buf[num] = '\0';
+            }
+
+            log_f("su \"%s\" invocation failed: %s", prog, buf);
+            rv = -1;
+        }
+
+        close(out_p[0]);
+    } else {
+        log_f("fork() failed[%d]: %s", errno, strerror(errno));
+        close(in_p[0]);
+        close(in_p[1]);
+        close(out_p[0]);
+        close(out_p[1]);
+        return -1;
+    }
+
+    return rv;
+}

app/src/main/jni/common/utils.h

@@ -62,5 +62,6 @@ void tupleSwapPeers(zdtun_5tuple_t *tuple);
 char loglvl2char(int lvl);
 char* humanSize(char *buf, int bufsize, double bytes);
 void hexdump(const char *buf, size_t bufsize);
+int run_shell_cmd(const char *prog, const char *args, bool as_root, bool check_error);
 
 #endif // __LOG_UTILS_H__

app/src/main/jni/core/capture_root.c

@@ -19,16 +19,11 @@
 
 #include <sys/un.h>
 #include <linux/limits.h>
-#include <sys/wait.h>
-#include <paths.h>
 #include "pcapdroid.h"
 #include "pcapd/pcapd.h"
 #include "common/utils.h"
 #include "third_party/uthash.h"
 
-// Needed for local compilation, don't remove
-extern char **environ;
-
 #ifdef FUZZING
 extern int openPcap(pcapdroid_t *pd);
 extern int nextPacket(pcapdroid_t *pd, pcapd_hdr_t *hdr, char *buf, size_t bufsize);
@@ -50,81 +45,6 @@ typedef struct pcap_conn_t {
 
 /* ******************************************************* */
 
-static int run_cmd(const char *prog, const char *args, bool as_root, bool check_error) {
-    int in_p[2], out_p[2];
-    int rv = -1;
-    pid_t pid;
-
-    if((pipe(in_p) != 0) || (pipe(out_p) != 0)) {
-        log_f("pipe failed[%d]: %s", errno, strerror(errno));
-        return -1;
-    }
-
-    if((pid = fork()) == 0) {
-        // child
-        char *argp[] = {"sh", "-c", as_root ? "su" : "sh", NULL};
-
-        close(in_p[1]);
-        close(out_p[0]);
-
-        dup2(in_p[0], STDIN_FILENO);
-        dup2(out_p[1], STDOUT_FILENO);
-        dup2(out_p[1], STDERR_FILENO);
-
-        execve(_PATH_BSHELL, argp, environ);
-        fprintf(stderr, "execve failed[%d]: %s", errno, strerror(errno));
-        exit(1);
-    } else if(pid > 0) {
-        // parent
-        int out = out_p[0];
-        close(in_p[0]);
-        close(out_p[1]);
-
-        // write "su" command input
-        log_d("run_cmd[%d]: %s %s", pid, prog, args);
-        write(in_p[1], prog, strlen(prog));
-        write(in_p[1], " ", 1);
-        write(in_p[1], args, strlen(args));
-        write(in_p[1], "\n", 1);
-        close(in_p[1]);
-
-        waitpid(pid, &rv, 0);
-
-        if(check_error && (rv != 0)) {
-            char buf[128];
-            struct timeval timeout = {0};
-            fd_set fds;
-
-            buf[0] = '\0';
-            FD_ZERO(&fds);
-            FD_SET(out, &fds);
-
-            select(out + 1, &fds, NULL, NULL, &timeout);
-            if (FD_ISSET(out, &fds)) {
-                int num = read(out, buf, sizeof(buf) - 1);
-                if (num > 0)
-                    buf[num] = '\0';
-            }
-
-            log_f("su \"%s\" invocation failed: %s", prog, buf);
-            rv = -1;
-        }
-
-        close(out_p[0]);
-    } else {
-        log_f("fork() failed[%d]: %s", errno, strerror(errno));
-        close(in_p[0]);
-        close(in_p[1]);
-        close(out_p[0]);
-        close(out_p[1]);
-        return -1;
-    }
-
-    return rv;
-}
-
-/* ******************************************************* */
-
 static void kill_pcapd(pcapdroid_t *nc) {
     int pid;
     char pid_s[8];
@@ -138,7 +58,7 @@ static void kill_pcapd(pcapdroid_t *nc) {
 
     if(pid != 0) {
         log_d("Killing old pcapd with pid %d", pid);
-        run_cmd("kill", pid_s, true, false);
+        run_shell_cmd("kill", pid_s, true, false);
     }
 
     fclose(f);
@@ -244,7 +164,7 @@ static int connectPcapd(pcapdroid_t *pd) {
     // Start the daemon
     char args[256];
     snprintf(args, sizeof(args), "-l pcapd.log -i '%s' -d -u %d -t -b '%s'", pd->root.capture_interface, pd->app_filter, bpf);
-    if(run_cmd(pcapd, args, pd->root.as_root, true) != 0)
+    if(run_shell_cmd(pcapd, args, pd->root.as_root, true) != 0)
         goto cleanup;
 
     // Wait for pcapd to start

app/src/main/jni/core/jni_impl.c

@@ -793,6 +793,19 @@ Java_com_emanuelef_remote_1capture_CaptureService_nativeSetFirewallEnabled(JNIEn
 
 /* ******************************************************* */
 
+JNIEXPORT int JNICALL
+Java_com_emanuelef_remote_1capture_CaptureService_rootCmd(JNIEnv *env, jclass clazz, jstring prog,
+                                                          jstring args) {
+    const char *prog_s = (*env)->GetStringUTFChars(env, prog, 0);
+    const char *args_s = (*env)->GetStringUTFChars(env, args, 0);
+    int rv = run_shell_cmd(prog_s, args_s, true, true);
+
+    (*env)->ReleaseStringUTFChars(env, prog, prog_s);
+    (*env)->ReleaseStringUTFChars(env, args, args_s);
+
+    return rv;
+}
+
 char* getStringPref(pcapdroid_t *pd, const char *key, char *buf, int bufsize) {
     JNIEnv *env = pd->env;
 
@@ -904,5 +917,4 @@ void getApplicationByUid(pcapdroid_t *pd, jint uid, char *buf, int bufsize) {
     if(obj) (*env)->DeleteLocalRef(env, obj);
 }
 
-#endif // ANDROID
-
+#endif // ANDROID

app/src/main/res/values/strings.xml

@@ -359,4 +359,6 @@
     <string name="app_intro_firewall_msg">With the integrated <a href='%1$s'>Firewall</a> you can easily block Internet access to individual apps and domains\n\nCombine this with the built-in traffic visibility to get the ultimate tool to protect your privacy</string>
     <string name="app_intro_malware_detection">Enhance the security of your device with the <a href='%1$s'>malware detection</a> feature\n\nBy using up-to-date blacklists, it can detect, block and alert malicious connections in real-time</string>
     <string name="app_intro_traffic_dump">PCAPdroid provides <a href='%1$s'>multiple ways</a> to dump the traffic in the standard PCAP format for further analysis\n\nVia the <a href='%2$s'>trailer option</a>, you can add app names to the packets and display them in Wireshark</string>
+    <string name="permission_granted">%1$s permission was granted</string>
+    <string name="permission_grant_fail">%1$s permission could not be granted</string>
 </resources>