1 // Copyright 2019 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "host/commands/process_sandboxer/filesystem.h"
16
17 #include <sys/stat.h>
18
19 #include <deque>
20 #include <initializer_list>
21 #include <string>
22 #include <string_view>
23
24 #include <absl/strings/str_cat.h>
25 #include <absl/strings/str_join.h>
26 #include <absl/strings/str_split.h>
27 #include <absl/strings/strip.h>
28
29 namespace cuttlefish::process_sandboxer {
30
31 // Copied from sandboxed_api/util/path.cc
32
33 namespace internal {
34
35 constexpr char kPathSeparator[] = "/";
36
JoinPathImpl(std::initializer_list<absl::string_view> paths)37 std::string JoinPathImpl(std::initializer_list<absl::string_view> paths) {
38 std::string result;
39 for (const auto& path : paths) {
40 if (path.empty()) {
41 continue;
42 }
43 if (result.empty()) {
44 absl::StrAppend(&result, path);
45 continue;
46 }
47 const auto comp = absl::StripPrefix(path, kPathSeparator);
48 if (absl::EndsWith(result, kPathSeparator)) {
49 absl::StrAppend(&result, comp);
50 } else {
51 absl::StrAppend(&result, kPathSeparator, comp);
52 }
53 }
54 return result;
55 }
56
57 } // namespace internal
58
59 // Copied from sandboxed_api/util/fileops.cc
60
61 namespace {
62
StripBasename(std::string_view path)63 std::string StripBasename(std::string_view path) {
64 const auto last_slash = path.find_last_of('/');
65 if (last_slash == std::string::npos) {
66 return "";
67 }
68 if (last_slash == 0) {
69 return "/";
70 }
71 return std::string(path.substr(0, last_slash));
72 }
73
74 } // namespace
75
CreateDirectoryRecursively(const std::string & path,int mode)76 bool CreateDirectoryRecursively(const std::string& path, int mode) {
77 if (mkdir(path.c_str(), mode) == 0 || errno == EEXIST) {
78 return true;
79 }
80
81 // We couldn't create the dir for reasons we can't handle.
82 if (errno != ENOENT) {
83 return false;
84 }
85
86 // The ENOENT case, the parent directory doesn't exist yet.
87 // Let's create it.
88 const std::string dir = StripBasename(path);
89 if (dir == "/" || dir.empty()) {
90 return false;
91 }
92 if (!CreateDirectoryRecursively(dir, mode)) {
93 return false;
94 }
95
96 // Now the parent dir exists, retry creating the directory.
97 return mkdir(path.c_str(), mode) == 0;
98 }
99
CleanPath(const std::string_view unclean_path)100 std::string CleanPath(const std::string_view unclean_path) {
101 int dotdot_num = 0;
102 std::deque<absl::string_view> parts;
103 for (absl::string_view part :
104 absl::StrSplit(unclean_path, '/', absl::SkipEmpty())) {
105 if (part == "..") {
106 if (parts.empty()) {
107 ++dotdot_num;
108 } else {
109 parts.pop_back();
110 }
111 } else if (part != ".") {
112 parts.push_back(part);
113 }
114 }
115 if (absl::StartsWith(unclean_path, "/")) {
116 if (parts.empty()) {
117 return "/";
118 }
119 parts.push_front("");
120 } else {
121 for (; dotdot_num; --dotdot_num) {
122 parts.push_front("..");
123 }
124 if (parts.empty()) {
125 return ".";
126 }
127 }
128 return absl::StrJoin(parts, "/");
129 }
130
131 } // namespace cuttlefish::process_sandboxer
132