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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "diagnose_usb.h"
     18 
     19 #include <errno.h>
     20 #include <unistd.h>
     21 
     22 #include <string>
     23 
     24 #include <android-base/stringprintf.h>
     25 
     26 #if defined(__linux__)
     27 #include <grp.h>
     28 #include <pwd.h>
     29 #endif
     30 
     31 static const char kPermissionsHelpUrl[] = "http://developer.android.com/tools/device.html";
     32 
     33 // Returns a message describing any potential problems we find with udev, or an empty string if we
     34 // can't find plugdev information (i.e. udev is not installed).
     35 static std::string GetUdevProblem() {
     36 #if defined(__linux__)
     37     errno = 0;
     38     group* plugdev_group = getgrnam("plugdev");
     39 
     40     if (plugdev_group == nullptr) {
     41         if (errno != 0) {
     42             perror("failed to read plugdev group info");
     43         }
     44         // We can't give any generally useful advice here, just let the caller print the help URL.
     45         return "";
     46     }
     47 
     48     // getgroups(2) indicates that the GNU group_member(3) may not check the egid so we check it
     49     // additionally just to be sure.
     50     if (group_member(plugdev_group->gr_gid) || getegid() == plugdev_group->gr_gid) {
     51         // The user is in plugdev so the problem is likely with the udev rules.
     52         return "user in plugdev group; are your udev rules wrong?";
     53     }
     54     passwd* pwd = getpwuid(getuid());
     55     return android::base::StringPrintf("user %s is not in the plugdev group",
     56                                        pwd ? pwd->pw_name : "?");
     57 #else
     58     return "";
     59 #endif
     60 }
     61 
     62 // Short help text must be a single line, and will look something like:
     63 //
     64 //   no permissions (reason); see [URL]
     65 std::string UsbNoPermissionsShortHelpText() {
     66     std::string help_text = "no permissions";
     67 
     68     std::string problem(GetUdevProblem());
     69     if (!problem.empty()) help_text += " (" + problem + ")";
     70 
     71     return android::base::StringPrintf("%s; see [%s]", help_text.c_str(), kPermissionsHelpUrl);
     72 }
     73 
     74 // Long help text can span multiple lines but doesn't currently provide more detailed information:
     75 //
     76 //   insufficient permissions for device: reason
     77 //   See [URL] for more information
     78 std::string UsbNoPermissionsLongHelpText() {
     79     std::string header = "insufficient permissions for device";
     80 
     81     std::string problem(GetUdevProblem());
     82     if (!problem.empty()) header += ": " + problem;
     83 
     84     return android::base::StringPrintf("%s\nSee [%s] for more information", header.c_str(),
     85                                        kPermissionsHelpUrl);
     86 }
     87