Botan  2.12.1
Crypto and TLS for C++11
system_rng.cpp
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1 /*
2 * System RNG
3 * (C) 2014,2015,2017,2018 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #include <botan/system_rng.h>
9 
10 #if defined(BOTAN_TARGET_OS_HAS_RTLGENRANDOM)
11  #include <botan/dyn_load.h>
12  #define NOMINMAX 1
13  #define _WINSOCKAPI_ // stop windows.h including winsock.h
14  #include <windows.h>
15 
16 #elif defined(BOTAN_TARGET_OS_HAS_CRYPTO_NG)
17  #include <bcrypt.h>
18 
19 #elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
20  #include <stdlib.h>
21 
22 #elif defined(BOTAN_TARGET_OS_HAS_GETRANDOM)
23  #include <sys/random.h>
24  #include <errno.h>
25 
26 #elif defined(BOTAN_TARGET_OS_HAS_DEV_RANDOM)
27  #include <sys/types.h>
28  #include <sys/stat.h>
29  #include <fcntl.h>
30  #include <unistd.h>
31  #include <errno.h>
32 #endif
33 
34 namespace Botan {
35 
36 namespace {
37 
38 #if defined(BOTAN_TARGET_OS_HAS_RTLGENRANDOM)
39 
40 class System_RNG_Impl final : public RandomNumberGenerator
41  {
42  public:
43  System_RNG_Impl() : m_advapi("advapi32.dll")
44  {
45  // This throws if the function is not found
46  m_rtlgenrandom = m_advapi.resolve<RtlGenRandom_fptr>("SystemFunction036");
47  }
48 
49  void randomize(uint8_t buf[], size_t len) override
50  {
51  bool success = m_rtlgenrandom(buf, ULONG(len)) == TRUE;
52  if(!success)
53  throw System_Error("RtlGenRandom failed");
54  }
55 
56  void add_entropy(const uint8_t[], size_t) override { /* ignored */ }
57  bool is_seeded() const override { return true; }
58  bool accepts_input() const override { return false; }
59  void clear() override { /* not possible */ }
60  std::string name() const override { return "RtlGenRandom"; }
61  private:
62  // Use type BYTE instead of BOOLEAN because of a naming conflict
63  // https://msdn.microsoft.com/en-us/library/windows/desktop/aa387694(v=vs.85).aspx
64  // https://msdn.microsoft.com/en-us/library/windows/desktop/aa383751(v=vs.85).aspx
65  using RtlGenRandom_fptr = BYTE (NTAPI *)(PVOID, ULONG);
66 
67  Dynamically_Loaded_Library m_advapi;
68  RtlGenRandom_fptr m_rtlgenrandom;
69  };
70 
71 #elif defined(BOTAN_TARGET_OS_HAS_CRYPTO_NG)
72 
73 class System_RNG_Impl final : public RandomNumberGenerator
74  {
75  public:
76  System_RNG_Impl()
77  {
78  NTSTATUS ret = ::BCryptOpenAlgorithmProvider(&m_prov,
79  BCRYPT_RNG_ALGORITHM,
80  MS_PRIMITIVE_PROVIDER, 0);
81  if(ret != STATUS_SUCCESS)
82  throw System_Error("System_RNG failed to acquire crypto provider", ret);
83  }
84 
85  ~System_RNG_Impl()
86  {
87  ::BCryptCloseAlgorithmProvider(m_prov, 0);
88  }
89 
90  void randomize(uint8_t buf[], size_t len) override
91  {
92  NTSTATUS ret = ::BCryptGenRandom(m_prov, static_cast<PUCHAR>(buf), static_cast<ULONG>(len), 0);
93  if(ret != STATUS_SUCCESS)
94  throw System_Error("System_RNG call to BCryptGenRandom failed", ret);
95  }
96 
97  void add_entropy(const uint8_t in[], size_t length) override
98  {
99  /*
100  There is a flag BCRYPT_RNG_USE_ENTROPY_IN_BUFFER to provide
101  entropy inputs, but it is ignored in Windows 8 and later.
102  */
103  }
104 
105  bool is_seeded() const override { return true; }
106  bool accepts_input() const override { return false; }
107  void clear() override { /* not possible */ }
108  std::string name() const override { return "crypto_ng"; }
109  private:
110  BCRYPT_ALG_HANDLE m_prov;
111  };
112 
113 #elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
114 
115 class System_RNG_Impl final : public RandomNumberGenerator
116  {
117  public:
118  // No constructor or destructor needed as no userland state maintained
119 
120  void randomize(uint8_t buf[], size_t len) override
121  {
122  ::arc4random_buf(buf, len);
123  }
124 
125  bool accepts_input() const override { return false; }
126  void add_entropy(const uint8_t[], size_t) override { /* ignored */ }
127  bool is_seeded() const override { return true; }
128  void clear() override { /* not possible */ }
129  std::string name() const override { return "arc4random"; }
130  };
131 
132 #elif defined(BOTAN_TARGET_OS_HAS_GETRANDOM)
133 
134 class System_RNG_Impl final : public RandomNumberGenerator
135  {
136  public:
137  // No constructor or destructor needed as no userland state maintained
138 
139  void randomize(uint8_t buf[], size_t len) override
140  {
141  const unsigned int flags = 0;
142 
143  while(len > 0)
144  {
145  const ssize_t got = ::getrandom(buf, len, flags);
146 
147  if(got < 0)
148  {
149  if(errno == EINTR)
150  continue;
151  throw System_Error("System_RNG getrandom failed", errno);
152  }
153 
154  buf += got;
155  len -= got;
156  }
157  }
158 
159  bool accepts_input() const override { return false; }
160  void add_entropy(const uint8_t[], size_t) override { /* ignored */ }
161  bool is_seeded() const override { return true; }
162  void clear() override { /* not possible */ }
163  std::string name() const override { return "getrandom"; }
164  };
165 
166 
167 #elif defined(BOTAN_TARGET_OS_HAS_DEV_RANDOM)
168 
169 // Read a random device
170 
171 class System_RNG_Impl final : public RandomNumberGenerator
172  {
173  public:
174  System_RNG_Impl()
175  {
176 #ifndef O_NOCTTY
177 #define O_NOCTTY 0
178 #endif
179 
180  m_fd = ::open(BOTAN_SYSTEM_RNG_DEVICE, O_RDWR | O_NOCTTY);
181 
182  if(m_fd >= 0)
183  {
184  m_writable = true;
185  }
186  else
187  {
188  /*
189  Cannot open in read-write mode. Fall back to read-only,
190  calls to add_entropy will fail, but randomize will work
191  */
192  m_fd = ::open(BOTAN_SYSTEM_RNG_DEVICE, O_RDONLY | O_NOCTTY);
193  m_writable = false;
194  }
195 
196  if(m_fd < 0)
197  throw System_Error("System_RNG failed to open RNG device", errno);
198  }
199 
200  ~System_RNG_Impl()
201  {
202  ::close(m_fd);
203  m_fd = -1;
204  }
205 
206  void randomize(uint8_t buf[], size_t len) override;
207  void add_entropy(const uint8_t in[], size_t length) override;
208  bool is_seeded() const override { return true; }
209  bool accepts_input() const override { return m_writable; }
210  void clear() override { /* not possible */ }
211  std::string name() const override { return BOTAN_SYSTEM_RNG_DEVICE; }
212  private:
213  int m_fd;
214  bool m_writable;
215  };
216 
217 void System_RNG_Impl::randomize(uint8_t buf[], size_t len)
218  {
219  while(len)
220  {
221  ssize_t got = ::read(m_fd, buf, len);
222 
223  if(got < 0)
224  {
225  if(errno == EINTR)
226  continue;
227  throw System_Error("System_RNG read failed", errno);
228  }
229  if(got == 0)
230  throw System_Error("System_RNG EOF on device"); // ?!?
231 
232  buf += got;
233  len -= got;
234  }
235  }
236 
237 void System_RNG_Impl::add_entropy(const uint8_t input[], size_t len)
238  {
239  if(!m_writable)
240  return;
241 
242  while(len)
243  {
244  ssize_t got = ::write(m_fd, input, len);
245 
246  if(got < 0)
247  {
248  if(errno == EINTR)
249  continue;
250 
251  /*
252  * This is seen on OS X CI, despite the fact that the man page
253  * for macOS urandom explicitly states that writing to it is
254  * supported, and write(2) does not document EPERM at all.
255  * But in any case EPERM seems indicative of a policy decision
256  * by the OS or sysadmin that additional entropy is not wanted
257  * in the system pool, so we accept that and return here,
258  * since there is no corrective action possible.
259  *
260  * In Linux EBADF or EPERM is returned if m_fd is not opened for
261  * writing.
262  */
263  if(errno == EPERM || errno == EBADF)
264  return;
265 
266  // maybe just ignore any failure here and return?
267  throw System_Error("System_RNG write failed", errno);
268  }
269 
270  input += got;
271  len -= got;
272  }
273  }
274 
275 #endif
276 
277 }
278 
280  {
281  static System_RNG_Impl g_system_rng;
282  return g_system_rng;
283  }
284 
285 }
RandomNumberGenerator & system_rng()
Definition: system_rng.cpp:279
int(* final)(unsigned char *, CTX *)
Flags flags(Flag flags)
Definition: p11.h:858
std::string name
#define O_NOCTTY
Definition: alg_id.cpp:13
#define TRUE
Definition: pkcs11t.h:31