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#endif
29
30static const char kPermissionsHelpUrl[] = "http://developer.android.com/tools/device.html";
31
32// Returns a message describing any potential problems we find with udev, or nullptr if we can't
33// find plugdev information (i.e. udev is not installed).
34static const char* GetUdevProblem() {
35#if defined(__linux__)
36    errno = 0;
37    group* plugdev_group = getgrnam("plugdev");
38
39    if (plugdev_group == nullptr) {
40        if (errno != 0) {
41            perror("failed to read plugdev group info");
42        }
43        // We can't give any generally useful advice here, just let the caller print the help URL.
44        return nullptr;
45    }
46
47    // getgroups(2) indicates that the group_member() may not check the egid so we check it
48    // additionally just to be sure.
49    if (group_member(plugdev_group->gr_gid) || getegid() == plugdev_group->gr_gid) {
50        // The user is in plugdev so the problem is likely with the udev rules.
51        return "verify udev rules";
52    }
53    return "udev requires plugdev group membership";
54#else
55    return nullptr;
56#endif
57}
58
59// Short help text must be a single line, and will look something like:
60//   no permissions (reason); see <URL>
61std::string UsbNoPermissionsShortHelpText() {
62    std::string help_text = "no permissions";
63
64    const char* problem = GetUdevProblem();
65    if (problem != nullptr) {
66        help_text += android::base::StringPrintf(" (%s)", problem);
67    }
68
69    return android::base::StringPrintf("%s; see [%s]", help_text.c_str(), kPermissionsHelpUrl);
70}
71
72// Long help text can span multiple lines and should provide more detailed information.
73std::string UsbNoPermissionsLongHelpText() {
74    std::string header = "insufficient permissions for device";
75
76    const char* problem = GetUdevProblem();
77    if (problem != nullptr) {
78        header += android::base::StringPrintf(": %s", problem);
79    }
80
81    return android::base::StringPrintf("%s.\nSee [%s] for more information.",
82                                       header.c_str(), kPermissionsHelpUrl);
83}
84