1 /*
2 * Copyright (C) 2018 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 "common/libs/utils/users.h"
18
19 #include <grp.h>
20 #include <pwd.h>
21 #include <sys/types.h>
22 #include <unistd.h>
23
24 #include <algorithm>
25 #include <cerrno>
26 #include <cstdlib>
27 #include <cstring>
28 #include <mutex>
29 #include <ostream>
30 #include <string>
31 #include <vector>
32
33 #include <android-base/file.h>
34 #include <android-base/logging.h>
35
36 #include "common/libs/utils/contains.h"
37
38 namespace cuttlefish {
39 namespace {
GetSuplementaryGroups()40 std::vector<gid_t> GetSuplementaryGroups() {
41 int num_groups = getgroups(0, nullptr);
42 if (num_groups < 0) {
43 LOG(ERROR) << "Unable to get number of supplementary groups: "
44 << std::strerror(errno);
45 return {};
46 }
47 std::vector<gid_t> groups(num_groups + 1);
48 int retval = getgroups(groups.size(), groups.data());
49 if (retval < 0) {
50 LOG(ERROR) << "Error obtaining list of supplementary groups (list size: "
51 << groups.size() << "): " << std::strerror(errno);
52 return {};
53 }
54 return groups;
55 }
56 } // namespace
57
GroupIdFromName(const std::string & group_name)58 gid_t GroupIdFromName(const std::string& group_name) {
59 struct group grp{};
60 struct group* grp_p{};
61 std::vector<char> buffer(100);
62 int result = 0;
63 while(true) {
64 result = getgrnam_r(group_name.c_str(), &grp, buffer.data(), buffer.size(),
65 &grp_p);
66 if (result != ERANGE) {
67 break;
68 }
69 buffer.resize(2*buffer.size());
70 }
71 if (result == 0) {
72 if (grp_p != nullptr) {
73 return grp.gr_gid;
74 } else {
75 // Caller may be checking with non-existent group name
76 return -1;
77 }
78 } else {
79 LOG(ERROR) << "Unable to get group id for group " << group_name << ": "
80 << std::strerror(result);
81 return -1;
82 }
83 }
84
InGroup(const std::string & group)85 bool InGroup(const std::string& group) {
86 auto gid = GroupIdFromName(group);
87 if (gid == static_cast<gid_t>(-1)) {
88 return false;
89 }
90
91 if (gid == getegid()) {
92 return true;
93 }
94
95 auto groups = GetSuplementaryGroups();
96 return Contains(groups, gid);
97 }
98
SystemWideUserHome()99 Result<std::string> SystemWideUserHome() {
100 auto uid = getuid();
101 // getpwuid() is not thread-safe, so we need a lock across all calls
102 static std::mutex getpwuid_mutex;
103 std::string home_dir;
104 {
105 std::lock_guard<std::mutex> lock(getpwuid_mutex);
106 const auto entry = getpwuid(uid);
107 if (entry) {
108 home_dir = entry->pw_dir;
109 }
110 endpwent();
111 if (home_dir.empty()) {
112 return CF_ERRNO("Failed to find the home directory using " << uid);
113 }
114 }
115 std::string home_realpath;
116 if (!android::base::Realpath(home_dir, &home_realpath)) {
117 return CF_ERRNO("Failed to convert " << home_dir << " to its Realpath");
118 }
119 return home_realpath;
120 }
121
122 } // namespace cuttlefish
123