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Add error reporting and fail for EAGAIN
Add error reporting strings for various error cases. This gives us much nicer and understandable error messages. SYS_getrandom() EAGAIN is now an error. Cryptography refuses to initialize its osrandom engine when the Kernel's CPRNG hasn't been seeded yet. Signed-off-by: Christian Heimes <[email protected]>
1 parent 8575fb2 commit 2abbab4

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2 files changed

+216
-32
lines changed

2 files changed

+216
-32
lines changed

‎src/_cffi_src/openssl/src/osrandom_engine.c

Lines changed: 184 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,11 @@ static int osrandom_init(ENGINE *e) {
3030
PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) {
3131
return 1;
3232
} else {
33+
ERR_Cryptography_OSRandom_error(
34+
CRYPTOGRAPHY_OSRANDOM_F_INIT,
35+
CRYPTOGRAPHY_OSRANDOM_R_CRYPTACQUIRECONTEXT,
36+
__FILE__, __LINE__
37+
);
3338
return 0;
3439
}
3540
}
@@ -40,8 +45,11 @@ static int osrandom_rand_bytes(unsigned char *buffer, int size) {
4045
}
4146

4247
if (!CryptGenRandom(hCryptProv, (DWORD)size, buffer)) {
43-
CRYPTOGRAPHY_OSRANDOM_put_error(
44-
"osrandom_engine.py:CryptGenRandom()");
48+
ERR_Cryptography_OSRandom_error(
49+
CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES,
50+
CRYPTOGRAPHY_OSRANDOM_R_CRYPTGENRANDOM,
51+
__FILE__, __LINE__
52+
);
4553
return 0;
4654
}
4755
return 1;
@@ -52,6 +60,11 @@ static int osrandom_finish(ENGINE *e) {
5260
hCryptProv = 0;
5361
return 1;
5462
} else {
63+
ERR_Cryptography_OSRandom_error(
64+
CRYPTOGRAPHY_OSRANDOM_F_FINISH,
65+
CRYPTOGRAPHY_OSRANDOM_R_CRYPTRELEASECONTEXT,
66+
__FILE__, __LINE__
67+
);
5568
return 0;
5669
}
5770
}
@@ -83,8 +96,11 @@ static int osrandom_rand_bytes(unsigned char *buffer, int size) {
8396
len = size > 256 ? 256 : size;
8497
res = getentropy(buffer, len);
8598
if (res < 0) {
86-
CRYPTOGRAPHY_OSRANDOM_put_error(
87-
"osrandom_engine.py:getentropy()");
99+
ERR_Cryptography_OSRandom_error(
100+
CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES,
101+
CRYPTOGRAPHY_OSRANDOM_R_GETENTROPY_FAILED,
102+
__FILE__, __LINE__
103+
);
88104
return 0;
89105
}
90106
buffer += len;
@@ -166,8 +182,11 @@ static int dev_urandom_fd(void) {
166182
n = close(fd);
167183
} while (n < 0 && errno == EINTR);
168184
}
169-
CRYPTOGRAPHY_OSRANDOM_put_error(
170-
"osrandom_engine.py:dev_urandom_fd()");
185+
ERR_Cryptography_OSRandom_error(
186+
CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_FD,
187+
CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_OPEN_FAILED,
188+
__FILE__, __LINE__
189+
);
171190
return -1;
172191
}
173192

@@ -186,8 +205,11 @@ static int dev_urandom_read(unsigned char *buffer, int size) {
186205
} while (n < 0 && errno == EINTR);
187206

188207
if (n <= 0) {
189-
CRYPTOGRAPHY_OSRANDOM_put_error(
190-
"osrandom_engine.py:dev_urandom_read()");
208+
ERR_Cryptography_OSRandom_error(
209+
CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_READ,
210+
CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_READ_FAILED,
211+
__FILE__, __LINE__
212+
);
191213
return 0;
192214
}
193215
buffer += n;
@@ -221,28 +243,51 @@ static void dev_urandom_close(void) {
221243
#if CRYPTOGRAPHY_OSRANDOM_ENGINE == CRYPTOGRAPHY_OSRANDOM_ENGINE_GETRANDOM
222244
static const char *Cryptography_osrandom_engine_name = "osrandom_engine getrandom()";
223245

224-
static int getrandom_works = -1;
246+
static int getrandom_works = CRYPTOGRAPHY_OSRANDOM_GETRANDOM_NOT_INIT;
225247

226248
static int osrandom_init(ENGINE *e) {
227249
/* We try to detect working getrandom until we succeed. */
228-
if (getrandom_works != 1) {
250+
if (getrandom_works != CRYPTOGRAPHY_OSRANDOM_GETRANDOM_WORKS) {
229251
long n;
230252
char dest[1];
231253
n = syscall(SYS_getrandom, dest, sizeof(dest), GRND_NONBLOCK);
232-
if (n < 0) {
233-
/* Can fail with:
234-
* - ENOSYS: Kernel does not support the syscall.
235-
* - ENOPERM: seccomp prevents syscall.
236-
* - EAGAIN: Kernel CRPNG has not been seeded yet.
237-
* EINTR cannot occur for buflen < 256.
238-
*/
239-
getrandom_works = 0;
254+
if (n == sizeof(dest)) {
255+
getrandom_works = CRYPTOGRAPHY_OSRANDOM_GETRANDOM_WORKS;
240256
} else {
241-
getrandom_works = 1;
257+
int e = errno;
258+
switch(e) {
259+
case ENOSYS:
260+
/* Fallback: Kernel does not support the syscall. */
261+
getrandom_works = CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK;
262+
break;
263+
case EPERM:
264+
/* Fallback: seccomp prevents syscall */
265+
getrandom_works = CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK;
266+
break;
267+
case EAGAIN:
268+
/* Failure: Kernel CRPNG has not been seeded yet */
269+
ERR_Cryptography_OSRandom_error(
270+
CRYPTOGRAPHY_OSRANDOM_F_INIT,
271+
CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_EAGAIN,
272+
__FILE__, __LINE__
273+
);
274+
getrandom_works = CRYPTOGRAPHY_OSRANDOM_GETRANDOM_INIT_FAILED;
275+
break;
276+
default:
277+
/* EINTR cannot occur for buflen < 256. */
278+
ERR_Cryptography_OSRandom_error(
279+
CRYPTOGRAPHY_OSRANDOM_F_INIT,
280+
CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_UNEXPECTED,
281+
"errno", e
282+
);
283+
getrandom_works = CRYPTOGRAPHY_OSRANDOM_GETRANDOM_INIT_FAILED;
284+
break;
285+
}
242286
}
243287
}
288+
244289
/* fallback to dev urandom */
245-
if (getrandom_works == 0) {
290+
if (getrandom_works == CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK) {
246291
int fd = dev_urandom_fd();
247292
if (fd < 0) {
248293
return 0;
@@ -252,25 +297,45 @@ static int osrandom_init(ENGINE *e) {
252297
}
253298

254299
static int osrandom_rand_bytes(unsigned char *buffer, int size) {
255-
if (getrandom_works == 1) {
256-
long n;
300+
long n;
301+
302+
switch(getrandom_works) {
303+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_INIT_FAILED:
304+
ERR_Cryptography_OSRandom_error(
305+
CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES,
306+
CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED,
307+
__FILE__, __LINE__
308+
);
309+
return 0;
310+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_NOT_INIT:
311+
ERR_Cryptography_OSRandom_error(
312+
CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES,
313+
CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_NOT_INIT,
314+
__FILE__, __LINE__
315+
);
316+
return 0;
317+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK:
318+
return dev_urandom_read(buffer, size);
319+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_WORKS:
257320
while (size > 0) {
258321
do {
259322
n = syscall(SYS_getrandom, buffer, size, GRND_NONBLOCK);
260323
} while (n < 0 && errno == EINTR);
261324

262325
if (n <= 0) {
263-
CRYPTOGRAPHY_OSRANDOM_put_error(
264-
"osrandom_engine.py:SYS_getrandom");
326+
ERR_Cryptography_OSRandom_error(
327+
CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES,
328+
CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_FAILED,
329+
__FILE__, __LINE__
330+
);
265331
return 0;
266332
}
267333
buffer += n;
268334
size -= n;
269335
}
270336
return 1;
271-
} else {
272-
return dev_urandom_read(buffer, size);
273337
}
338+
return 0; /* unreachable */
274339
}
275340

276341
static int osrandom_finish(ENGINE *e) {
@@ -279,17 +344,31 @@ static int osrandom_finish(ENGINE *e) {
279344
}
280345

281346
static int osrandom_rand_status(void) {
282-
if ((getrandom_works != 1) && (urandom_cache.fd < 0)) {
347+
switch(getrandom_works) {
348+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_INIT_FAILED:
349+
return 0;
350+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_NOT_INIT:
283351
return 0;
352+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK:
353+
return urandom_cache.fd >= 0;
354+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_WORKS:
355+
return 1;
284356
}
285-
return 1;
357+
return 0; /* unreachable */
286358
}
287359

288360
static const char *osurandom_get_implementation(void) {
289-
if (getrandom_works == 1) {
361+
switch(getrandom_works) {
362+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_INIT_FAILED:
363+
return "<failed>";
364+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_NOT_INIT:
365+
return "<not initialized>";
366+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK:
367+
return "/dev/urandom";
368+
case CRYPTOGRAPHY_OSRANDOM_GETRANDOM_WORKS:
290369
return "getrandom";
291370
}
292-
return "/dev/urandom";
371+
return "<invalid>"; /* unreachable */
293372
}
294373
#endif /* CRYPTOGRAPHY_OSRANDOM_ENGINE_GETRANDOM */
295374

@@ -384,10 +463,85 @@ static int osrandom_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f) (void))
384463
}
385464
}
386465

466+
/* error reporting */
467+
#define ERR_FUNC(func) ERR_PACK(0, func, 0)
468+
#define ERR_REASON(reason) ERR_PACK(0, 0, reason)
469+
470+
static ERR_STRING_DATA CRYPTOGRAPHY_OSRANDOM_lib_name[] = {
471+
{0, "osrandom_engine"},
472+
{0, NULL}
473+
};
474+
475+
static ERR_STRING_DATA CRYPTOGRAPHY_OSRANDOM_str_funcs[] = {
476+
{ERR_FUNC(CRYPTOGRAPHY_OSRANDOM_F_INIT),
477+
"osrandom_init"},
478+
{ERR_FUNC(CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES),
479+
"osrandom_rand_bytes"},
480+
{ERR_FUNC(CRYPTOGRAPHY_OSRANDOM_F_FINISH),
481+
"osrandom_finish"},
482+
{ERR_FUNC(CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_FD),
483+
"dev_urandom_fd"},
484+
{ERR_FUNC(CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_READ),
485+
"dev_urandom_read"},
486+
{0, NULL}
487+
};
488+
489+
static ERR_STRING_DATA CRYPTOGRAPHY_OSRANDOM_str_reasons[] = {
490+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_CRYPTACQUIRECONTEXT),
491+
"CryptAcquireContext() failed."},
492+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_CRYPTGENRANDOM),
493+
"CryptGenRandom() failed."},
494+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_CRYPTRELEASECONTEXT),
495+
"CryptReleaseContext() failed."},
496+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_GETENTROPY_FAILED),
497+
"getentropy() failed"},
498+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_OPEN_FAILED),
499+
"open('/dev/urandom') failed."},
500+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_READ_FAILED),
501+
"Reading from /dev/urandom fd failed."},
502+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED),
503+
"getrandom() initialization failed."},
504+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_EAGAIN),
505+
"getrandom() initialization failed with EAGAIN. Most likely Kernel "
506+
"CPRNG is not seeded yet."},
507+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_UNEXPECTED),
508+
"getrandom() initialization failed with unexpected errno."},
509+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_FAILED),
510+
"getrandom() syscall failed."},
511+
{ERR_REASON(CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_NOT_INIT),
512+
"getrandom() engine was not properly initialized."},
513+
{0, NULL}
514+
};
515+
516+
static int Cryptography_OSRandom_lib_error_code = 0;
517+
518+
static void ERR_load_Cryptography_OSRandom_strings(void)
519+
{
520+
if (Cryptography_OSRandom_lib_error_code == 0) {
521+
Cryptography_OSRandom_lib_error_code = ERR_get_next_error_library();
522+
ERR_load_strings(Cryptography_OSRandom_lib_error_code,
523+
CRYPTOGRAPHY_OSRANDOM_lib_name);
524+
ERR_load_strings(Cryptography_OSRandom_lib_error_code,
525+
CRYPTOGRAPHY_OSRANDOM_str_funcs);
526+
ERR_load_strings(Cryptography_OSRandom_lib_error_code,
527+
CRYPTOGRAPHY_OSRANDOM_str_reasons);
528+
}
529+
}
530+
531+
static void ERR_Cryptography_OSRandom_error(int function, int reason,
532+
char *file, int line)
533+
{
534+
ERR_PUT_error(Cryptography_OSRandom_lib_error_code, function, reason,
535+
file, line);
536+
}
537+
387538
/* Returns 1 if successfully added, 2 if engine has previously been added,
388539
and 0 for error. */
389540
int Cryptography_add_osrandom_engine(void) {
390541
ENGINE *e;
542+
543+
ERR_load_Cryptography_OSRandom_strings();
544+
391545
e = ENGINE_by_id(Cryptography_osrandom_engine_id);
392546
if (e != NULL) {
393547
ENGINE_free(e);

‎src/_cffi_src/openssl/src/osrandom_engine.h

Lines changed: 32 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -51,8 +51,38 @@
5151
#define CRYPTOGRAPHY_OSRANDOM_NEEDS_DEV_URANDOM 1
5252
#endif
5353

54-
#define CRYPTOGRAPHY_OSRANDOM_put_error(funcname) \
55-
ERR_put_error(ERR_LIB_RAND, 0, 0, funcname, 0)
54+
enum {
55+
CRYPTOGRAPHY_OSRANDOM_GETRANDOM_INIT_FAILED = -2,
56+
CRYPTOGRAPHY_OSRANDOM_GETRANDOM_NOT_INIT,
57+
CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK,
58+
CRYPTOGRAPHY_OSRANDOM_GETRANDOM_WORKS
59+
};
5660

5761
/* engine ctrl */
5862
#define CRYPTOGRAPHY_OSRANDOM_GET_IMPLEMENTATION ENGINE_CMD_BASE
63+
64+
/* error reporting */
65+
static void ERR_load_Cryptography_OSRandom_strings(void);
66+
static void ERR_Cryptography_OSRandom_error(int function, int reason,
67+
char *file, int line);
68+
69+
#define CRYPTOGRAPHY_OSRANDOM_F_INIT 100
70+
#define CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES 101
71+
#define CRYPTOGRAPHY_OSRANDOM_F_FINISH 102
72+
#define CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_FD 300
73+
#define CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_READ 301
74+
75+
#define CRYPTOGRAPHY_OSRANDOM_R_CRYPTACQUIRECONTEXT 100
76+
#define CRYPTOGRAPHY_OSRANDOM_R_CRYPTGENRANDOM 101
77+
#define CRYPTOGRAPHY_OSRANDOM_R_CRYPTRELEASECONTEXT 102
78+
79+
#define CRYPTOGRAPHY_OSRANDOM_R_GETENTROPY_FAILED 200
80+
81+
#define CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_OPEN_FAILED 300
82+
#define CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_READ_FAILED 301
83+
84+
#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED 400
85+
#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_EAGAIN 401
86+
#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_UNEXPECTED 402
87+
#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_FAILED 403
88+
#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_NOT_INIT 404

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