1 // Copyright 2006 Google LLC
2 //
3 // Redistribution and use in source and binary forms, with or without
4 // modification, are permitted provided that the following conditions are
5 // met:
6 //
7 // * Redistributions of source code must retain the above copyright
8 // notice, this list of conditions and the following disclaimer.
9 // * Redistributions in binary form must reproduce the above
10 // copyright notice, this list of conditions and the following disclaimer
11 // in the documentation and/or other materials provided with the
12 // distribution.
13 // * Neither the name of Google LLC nor the names of its
14 // contributors may be used to endorse or promote products derived from
15 // this software without specific prior written permission.
16 //
17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
20 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
21 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28
29 #ifdef HAVE_CONFIG_H
30 #include <config.h> // Must come first
31 #endif
32
33 #include "common/linux/eintr_wrapper.h"
34 #include "common/linux/guid_creator.h"
35
36 #include <assert.h>
37 #include <fcntl.h>
38 #include <pthread.h>
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <string.h>
42 #include <sys/stat.h>
43 #include <time.h>
44 #include <unistd.h>
45
46 #if defined(HAVE_SYS_RANDOM_H)
47 #include <sys/random.h>
48 #endif
49
50 //
51 // GUIDGenerator
52 //
53 // This class is used to generate random GUID.
54 // Currently use random number to generate a GUID since Linux has
55 // no native GUID generator. This should be OK since we don't expect
56 // crash to happen very offen.
57 //
58 class GUIDGenerator {
59 public:
BytesToUInt32(const uint8_t bytes[])60 static uint32_t BytesToUInt32(const uint8_t bytes[]) {
61 return ((uint32_t) bytes[0]
62 | ((uint32_t) bytes[1] << 8)
63 | ((uint32_t) bytes[2] << 16)
64 | ((uint32_t) bytes[3] << 24));
65 }
66
UInt32ToBytes(uint8_t bytes[],uint32_t n)67 static void UInt32ToBytes(uint8_t bytes[], uint32_t n) {
68 bytes[0] = n & 0xff;
69 bytes[1] = (n >> 8) & 0xff;
70 bytes[2] = (n >> 16) & 0xff;
71 bytes[3] = (n >> 24) & 0xff;
72 }
73
CreateGUID(GUID * guid)74 static bool CreateGUID(GUID *guid) {
75 #if defined(HAVE_ARC4RANDOM) // Android, BSD, ...
76 CreateGuidFromArc4Random(guid);
77 #else // Linux
78 bool success = false;
79
80 #if defined(HAVE_SYS_RANDOM_H) && defined(HAVE_GETRANDOM)
81 success = CreateGUIDFromGetrandom(guid);
82 #endif // HAVE_SYS_RANDOM_H && HAVE_GETRANDOM
83 if (!success) {
84 success = CreateGUIDFromDevUrandom(guid);
85 }
86
87 if (!success) {
88 CreateGUIDFromRand(guid);
89 success = true;
90 }
91 #endif
92
93 // Put in the version according to RFC 4122.
94 guid->data3 &= 0x0fff;
95 guid->data3 |= 0x4000;
96
97 // Put in the variant according to RFC 4122.
98 guid->data4[0] &= 0x3f;
99 guid->data4[0] |= 0x80;
100
101 return true;
102 }
103
104 private:
105 #ifdef HAVE_ARC4RANDOM
CreateGuidFromArc4Random(GUID * guid)106 static void CreateGuidFromArc4Random(GUID *guid) {
107 char *buf = reinterpret_cast<char*>(guid);
108
109 for (size_t i = 0; i < sizeof(GUID); i += sizeof(uint32_t)) {
110 uint32_t random_data = arc4random();
111
112 memcpy(buf + i, &random_data, sizeof(uint32_t));
113 }
114 }
115 #else
116 static void InitOnce() {
117 pthread_once(&once_control, &InitOnceImpl);
118 }
119
120 static void InitOnceImpl() {
121 // time(NULL) is a very poor seed, so lacking anything better mix an
122 // address into it. We drop the four rightmost bits as they're likely to
123 // be 0 on almost all architectures.
124 srand(time(NULL) | ((uintptr_t)&once_control >> 4));
125 }
126
127 static pthread_once_t once_control;
128
129 #if defined(HAVE_SYS_RANDOM_H) && defined(HAVE_GETRANDOM)
130 static bool CreateGUIDFromGetrandom(GUID *guid) {
131 char *buf = reinterpret_cast<char*>(guid);
132 int read_bytes = getrandom(buf, sizeof(GUID), GRND_NONBLOCK);
133
134 return (read_bytes == static_cast<int>(sizeof(GUID)));
135 }
136 #endif // HAVE_SYS_RANDOM_H && HAVE_GETRANDOM
137
138 // Populate the GUID using random bytes read from /dev/urandom, returns false
139 // if the GUID wasn't fully populated with random data.
140 static bool CreateGUIDFromDevUrandom(GUID *guid) {
141 char *buf = reinterpret_cast<char*>(guid);
142 int fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
143
144 if (fd == -1) {
145 return false;
146 }
147
148 ssize_t read_bytes = HANDLE_EINTR(read(fd, buf, sizeof(GUID)));
149 close(fd);
150
151 return (read_bytes == static_cast<ssize_t>(sizeof(GUID)));
152 }
153
154 // Populate the GUID using a stream of random bytes obtained from rand().
155 static void CreateGUIDFromRand(GUID *guid) {
156 char *buf = reinterpret_cast<char*>(guid);
157
158 InitOnce();
159
160 for (size_t i = 0; i < sizeof(GUID); i++) {
161 buf[i] = rand();
162 }
163 }
164 #endif
165 };
166
167 #ifndef HAVE_ARC4RANDOM
168 pthread_once_t GUIDGenerator::once_control = PTHREAD_ONCE_INIT;
169 #endif
170
CreateGUID(GUID * guid)171 bool CreateGUID(GUID *guid) {
172 return GUIDGenerator::CreateGUID(guid);
173 }
174
175 // Parse guid to string.
GUIDToString(const GUID * guid,char * buf,int buf_len)176 bool GUIDToString(const GUID *guid, char *buf, int buf_len) {
177 // Should allow more space the the max length of GUID.
178 assert(buf_len > kGUIDStringLength);
179 int num = snprintf(buf, buf_len, kGUIDFormatString,
180 guid->data1, guid->data2, guid->data3,
181 GUIDGenerator::BytesToUInt32(&(guid->data4[0])),
182 GUIDGenerator::BytesToUInt32(&(guid->data4[4])));
183 if (num != kGUIDStringLength)
184 return false;
185
186 buf[num] = '\0';
187 return true;
188 }
189