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Catch EPERM error in py_getrandom()

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Issue #27955: Fallback on reading /dev/urandom device when the getrandom()
syscall fails with EPERM, for example when blocked by SECCOMP.
This commit is contained in:
Victor Stinner 2016-09-20 22:46:02 +02:00
parent af59732102
commit 6d8bc46cc0
2 changed files with 11 additions and 7 deletions
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3
Misc/NEWS
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@ -10,6 +10,9 @@ Release date: TBA
Core and Builtins Core and Builtins
----------------- -----------------
- Issue #27955: Fallback on reading /dev/urandom device when the getrandom()
syscall fails with EPERM, for example when blocked by SECCOMP.
- Issue #28131: Fix a regression in zipimport's compile_source(). zipimport - Issue #28131: Fix a regression in zipimport's compile_source(). zipimport
should use the same optimization level as the interpreter. should use the same optimization level as the interpreter.

15
Python/random.c
View file

@ -121,8 +121,8 @@ py_getentropy(unsigned char *buffer, Py_ssize_t size, int fatal)
/* Call getrandom() /* Call getrandom()
- Return 1 on success - Return 1 on success
- Return 0 if getrandom() syscall is not available (failed with ENOSYS) - Return 0 if getrandom() syscall is not available (failed with ENOSYS or
or if getrandom(GRND_NONBLOCK) failed with EAGAIN (system urandom EPERM) or if getrandom(GRND_NONBLOCK) failed with EAGAIN (system urandom
not initialized yet) and raise=0. not initialized yet) and raise=0.
- Raise an exception (if raise is non-zero) and return -1 on error: - Raise an exception (if raise is non-zero) and return -1 on error:
getrandom() failed with EINTR and the Python signal handler raised an getrandom() failed with EINTR and the Python signal handler raised an
@ -131,7 +131,7 @@ static int
py_getrandom(void *buffer, Py_ssize_t size, int raise) py_getrandom(void *buffer, Py_ssize_t size, int raise)
{ {
/* Is getrandom() supported by the running kernel? Set to 0 if getrandom() /* Is getrandom() supported by the running kernel? Set to 0 if getrandom()
failed with ENOSYS. Need Linux kernel 3.17 or newer, or Solaris failed with ENOSYS or EPERM. Need Linux kernel 3.17 or newer, or Solaris
11.3 or newer */ 11.3 or newer */
static int getrandom_works = 1; static int getrandom_works = 1;
@ -182,8 +182,9 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise)
if (n < 0) { if (n < 0) {
/* ENOSYS: getrandom() syscall not supported by the kernel (but /* ENOSYS: getrandom() syscall not supported by the kernel (but
* maybe supported by the host which built Python). */ * maybe supported by the host which built Python). EPERM:
if (errno == ENOSYS) { * getrandom() syscall blocked by SECCOMP or something else. */
if (errno == ENOSYS || errno == EPERM) {
getrandom_works = 0; getrandom_works = 0;
return 0; return 0;
} }
@ -250,7 +251,7 @@ dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size)
if (py_getrandom(buffer, size, 0) == 1) { if (py_getrandom(buffer, size, 0) == 1) {
return; return;
} }
/* getrandom() failed with ENOSYS, /* getrandom() failed with ENOSYS or EPERM,
fall back on reading /dev/urandom */ fall back on reading /dev/urandom */
#endif #endif
@ -301,7 +302,7 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
if (res == 1) { if (res == 1) {
return 0; return 0;
} }
/* getrandom() failed with ENOSYS, /* getrandom() failed with ENOSYS or EPERM,
fall back on reading /dev/urandom */ fall back on reading /dev/urandom */
#endif #endif