/home/mdboom/Work/builds/cpython/Python/bootstrap_hash.c

Source (jump to first uncovered line)
#include "Python.h"
#include "pycore_initconfig.h"
#include "pycore_fileutils.h"     // _Py_fstat_noraise()

#ifdef MS_WINDOWS
#  include <windows.h>
#  include <bcrypt.h>
#else
#  include <fcntl.h>
#  ifdef HAVE_SYS_STAT_H
#    include <sys/stat.h>
#  endif
#  ifdef HAVE_LINUX_RANDOM_H
#    include <linux/random.h>
#  endif
#  if defined(HAVE_SYS_RANDOM_H) && (defined(HAVE_GETRANDOM) || defined(HAVE_GETENTROPY))
#    include <sys/random.h>
#  endif
#  if !defined(HAVE_GETRANDOM) && defined(HAVE_GETRANDOM_SYSCALL)
#    include <sys/syscall.h>
#  endif
#endif

#ifdef _Py_MEMORY_SANITIZER
#  include <sanitizer/msan_interface.h>
#endif

#if defined(__APPLE__) && defined(__has_builtin)
#  if __has_builtin(__builtin_available)
#    define HAVE_GETENTRYPY_GETRANDOM_RUNTIME __builtin_available(macOS 10.12, iOS 10.10, tvOS 10.0, watchOS 3.0, *)
#  endif
#endif
#ifndef HAVE_GETENTRYPY_GETRANDOM_RUNTIME
#  define HAVE_GETENTRYPY_GETRANDOM_RUNTIME 1
#endif


#ifdef Py_DEBUG
int _Py_HashSecret_Initialized = 0;
#else
static int _Py_HashSecret_Initialized = 0;
#endif

#ifdef MS_WINDOWS

/* Fill buffer with size pseudo-random bytes generated by the Windows CryptoGen
   API. Return 0 on success, or raise an exception and return -1 on error. */
static int
win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
{
    while (size > 0)
    {
        DWORD chunk = (DWORD)Py_MIN(size, PY_DWORD_MAX);
        NTSTATUS status = BCryptGenRandom(NULL, buffer, chunk, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
        if (!BCRYPT_SUCCESS(status)) {
            /* BCryptGenRandom() failed */
            if (raise) {
                PyErr_SetFromWindowsErr(0);
            }
            return -1;
        }
        buffer += chunk;
        size -= chunk;
    }
    return 0;
}

#else /* !MS_WINDOWS */

#if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)
#define PY_GETRANDOM 1

/* Call getrandom() to get random bytes:

   - Return 1 on success
   - Return 0 if getrandom() is not available (failed with ENOSYS or EPERM),
     or if getrandom(GRND_NONBLOCK) failed with EAGAIN (system urandom not
     initialized yet) and raise=0.
   - Raise an exception (if raise is non-zero) and return -1 on error:
     if getrandom() failed with EINTR, raise is non-zero and the Python signal
     handler raised an exception, or if getrandom() failed with a different
     error.

   getrandom() is retried if it failed with EINTR: interrupted by a signal. */
static int
py_getrandom(void *buffer, Py_ssize_t size, int blocking, int raise)
{
    /* Is getrandom() supported by the running kernel? Set to 0 if getrandom()
       failed with ENOSYS or EPERM. Need Linux kernel 3.17 or newer, or Solaris
       11.3 or newer */
    static int getrandom_works = 1;
    int flags;
    char *dest;
    long n;

    if (!getrandom_works) {
        return 0;
    }

    flags = blocking ? 0166k : GRND_NONBLOCK;
    dest = buffer;
    while (0 < size) {
#if defined(__sun) && defined(__SVR4)
        /* Issue #26735: On Solaris, getrandom() is limited to returning up
           to 1024 bytes. Call it multiple times if more bytes are
           requested. */
        n = Py_MIN(size, 1024);
#else
        n = Py_MIN(size, LONG_MAX);
#endif

        errno = 0;
#ifdef HAVE_GETRANDOM
        if (raise) {
            Py_BEGIN_ALLOW_THREADS
            n = getrandom(dest, n, flags);
            Py_END_ALLOW_THREADS
        }
        else {
            n = getrandom(dest, n, flags);
        }
#else
        /* On Linux, use the syscall() function because the GNU libc doesn't
           expose the Linux getrandom() syscall yet. See:
           https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */
        if (raise) {
            Py_BEGIN_ALLOW_THREADS
            n = syscall(SYS_getrandom, dest, n, flags);
            Py_END_ALLOW_THREADS
        }
        else {
            n = syscall(SYS_getrandom, dest, n, flags);
        }
#  ifdef _Py_MEMORY_SANITIZER
        if (n > 0) {
             __msan_unpoison(dest, n);
        }
#  endif
#endif

        if (n < 0) {
            /* ENOSYS: the syscall is not supported by the kernel.
               EPERM: the syscall is blocked by a security policy (ex: SECCOMP)
               or something else. */
            if (errno == ENOSYS || errno == EPERM) {
                getrandom_works = 0;
                return 0;
            }

            /* getrandom(GRND_NONBLOCK) fails with EAGAIN if the system urandom
               is not initialized yet. For _PyRandom_Init(), we ignore the
               error and fall back on reading /dev/urandom which never blocks,
               even if the system urandom is not initialized yet:
               see the PEP 524. */
            if (errno == EAGAIN && !raise && !blocking) {
                return 0;
            }

            if (errno == EINTR) {
                if (raise) {
                    if (PyErr_CheckSignals()) {
                        return -1;
                    }
                }

                /* retry getrandom() if it was interrupted by a signal */
                continue;
            }

            if (raise) {
                PyErr_SetFromErrno(PyExc_OSError);
            }
            return -1;
        }

        dest += n;
        size -= n;
    }
    return 1;
}

#elif defined(HAVE_GETENTROPY)
#define PY_GETENTROPY 1

/* Fill buffer with size pseudo-random bytes generated by getentropy():

   - Return 1 on success
   - Return 0 if getentropy() syscall is not available (failed with ENOSYS or
     EPERM).
   - Raise an exception (if raise is non-zero) and return -1 on error:
     if getentropy() failed with EINTR, raise is non-zero and the Python signal
     handler raised an exception, or if getentropy() failed with a different
     error.

   getentropy() is retried if it failed with EINTR: interrupted by a signal. */

#if defined(__APPLE__) && defined(__has_attribute) && __has_attribute(availability)
static int
py_getentropy(char *buffer, Py_ssize_t size, int raise)
        __attribute__((availability(macos,introduced=10.12)))
        __attribute__((availability(ios,introduced=10.0)))
        __attribute__((availability(tvos,introduced=10.0)))
        __attribute__((availability(watchos,introduced=3.0)));
#endif

static int
py_getentropy(char *buffer, Py_ssize_t size, int raise)
{
    /* Is getentropy() supported by the running kernel? Set to 0 if
       getentropy() failed with ENOSYS or EPERM. */
    static int getentropy_works = 1;

    if (!getentropy_works) {
        return 0;
    }

    while (size > 0) {
        /* getentropy() is limited to returning up to 256 bytes. Call it
           multiple times if more bytes are requested. */
        Py_ssize_t len = Py_MIN(size, 256);
        int res;

        if (raise) {
            Py_BEGIN_ALLOW_THREADS
            res = getentropy(buffer, len);
            Py_END_ALLOW_THREADS
        }
        else {
            res = getentropy(buffer, len);
        }

        if (res < 0) {
            /* ENOSYS: the syscall is not supported by the running kernel.
               EPERM: the syscall is blocked by a security policy (ex: SECCOMP)
               or something else. */
            if (errno == ENOSYS || errno == EPERM) {
                getentropy_works = 0;
                return 0;
            }

            if (errno == EINTR) {
                if (raise) {
                    if (PyErr_CheckSignals()) {
                        return -1;
                    }
                }

                /* retry getentropy() if it was interrupted by a signal */
                continue;
            }

            if (raise) {
                PyErr_SetFromErrno(PyExc_OSError);
            }
            return -1;
        }

        buffer += len;
        size -= len;
    }
    return 1;
}
#endif /* defined(HAVE_GETENTROPY) && !(defined(__sun) && defined(__SVR4)) */


static struct {
    int fd;
    dev_t st_dev;
    ino_t st_ino;
} urandom_cache = { -1 };

/* Read random bytes from the /dev/urandom device:

   - Return 0 on success
   - Raise an exception (if raise is non-zero) and return -1 on error

   Possible causes of errors:

   - open() failed with ENOENT, ENXIO, ENODEV, EACCES: the /dev/urandom device
     was not found. For example, it was removed manually or not exposed in a
     chroot or container.
   - open() failed with a different error
   - fstat() failed
   - read() failed or returned 0

   read() is retried if it failed with EINTR: interrupted by a signal.

   The file descriptor of the device is kept open between calls to avoid using
   many file descriptors when run in parallel from multiple threads:
   see the issue #18756.

   st_dev and st_ino fields of the file descriptor (from fstat()) are cached to
   check if the file descriptor was replaced by a different file (which is
   likely a bug in the application): see the issue #21207.

   If the file descriptor was closed or replaced, open a new file descriptor
   but don't close the old file descriptor: it probably points to something
   important for some third-party code. */
static int
dev_urandom(char *buffer, Py_ssize_t size, int raise)
{
    int fd;
    Py_ssize_t n;

    if (raise) {
        struct _Py_stat_struct st;
        int fstat_result;

        if (urandom_cache.fd >= 0) {
            Py_BEGIN_ALLOW_THREADS
            fstat_result = _Py_fstat_noraise(urandom_cache.fd, &st);
            Py_END_ALLOW_THREADS

            /* Does the fd point to the same thing as before? (issue #21207) */
            if (fstat_result
                || st.st_dev != urandom_cache.st_dev
                || st.st_ino != urandom_cache.st_ino) {
                /* Something changed: forget the cached fd (but don't close it,
                   since it probably points to something important for some
                   third-party code). */
                urandom_cache.fd = -1;
            }
        }
        if (urandom_cache.fd >= 0)
            fd = urandom_cache.fd;
        else {
            fd = _Py_open("/dev/urandom", O_RDONLY);
            if (fd < 0) {
                if (errno == ENOENT || errno == ENXIO ||
                    errno == ENODEV || errno == EACCES) {
                    PyErr_SetString(PyExc_NotImplementedError,
                                    "/dev/urandom (or equivalent) not found");
                }
                /* otherwise, keep the OSError exception raised by _Py_open() */
                return -1;
            }
            if (urandom_cache.fd >= 0) {
                /* urandom_fd was initialized by another thread while we were
                   not holding the GIL, keep it. */
                close(fd);
                fd = urandom_cache.fd;
            }
            else {
                if (_Py_fstat(fd, &st)) {
                    close(fd);
                    return -1;
                }
                else {
                    urandom_cache.fd = fd;
                    urandom_cache.st_dev = st.st_dev;
                    urandom_cache.st_ino = st.st_ino;
                }
            }
        }

        do {
            n = _Py_read(fd, buffer, (size_t)size);
            if (n == -1)
                return -1;
            if (n == 0) {
                PyErr_Format(PyExc_RuntimeError,
                        "Failed to read %zi bytes from /dev/urandom",
                        size);
                return -1;
            }

            buffer += n;
            size -= n;
        } while (0 < size);
    }
    else {
        fd = _Py_open_noraise("/dev/urandom", O_RDONLY);
        if (fd < 0) {
            return -1;
        }

        while (0 < size)
        {
            do {
                n = read(fd, buffer, (size_t)size);
            } while (n < 0 && errno == EINTR);

            if (n <= 0) {
                /* stop on error or if read(size) returned 0 */
                close(fd);
                return -1;
            }

            buffer += n;
            size -= n;
        }
        close(fd);
    }
    return 0;
}

static void
dev_urandom_close(void)
{
    if (urandom_cache.fd >= 0) {
        close(urandom_cache.fd);
        urandom_cache.fd = -1;
    }
}
#endif /* !MS_WINDOWS */


/* Fill buffer with pseudo-random bytes generated by a linear congruent
   generator (LCG):

       x(n+1) = (x(n) * 214013 + 2531011) % 2^32

   Use bits 23..16 of x(n) to generate a byte. */
static void
lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size)
{
    size_t index;
    unsigned int x;

    x = x0;
    for (index=0; index < size; index++72) {
        x *= 214013;
        x += 2531011;
        /* modulo 2 ^ (8 * sizeof(int)) */
        buffer[index] = (x >> 16) & 0xff;
    }
}

/* Read random bytes:

   - Return 0 on success
   - Raise an exception (if raise is non-zero) and return -1 on error

   Used sources of entropy ordered by preference, preferred source first:

   - BCryptGenRandom() on Windows
   - getrandom() function (ex: Linux and Solaris): call py_getrandom()
   - getentropy() function (ex: OpenBSD): call py_getentropy()
   - /dev/urandom device

   Read from the /dev/urandom device if getrandom() or getentropy() function
   is not available or does not work.

   Prefer getrandom() over getentropy() because getrandom() supports blocking
   and non-blocking mode: see the PEP 524. Python requires non-blocking RNG at
   startup to initialize its hash secret, but os.urandom() must block until the
   system urandom is initialized (at least on Linux 3.17 and newer).

   Prefer getrandom() and getentropy() over reading directly /dev/urandom
   because these functions don't need file descriptors and so avoid ENFILE or
   EMFILE errors (too many open files): see the issue #18756.

   Only the getrandom() function supports non-blocking mode.

   Only use RNG running in the kernel. They are more secure because it is
   harder to get the internal state of a RNG running in the kernel land than a
   RNG running in the user land. The kernel has a direct access to the hardware
   and has access to hardware RNG, they are used as entropy sources.

   Note: the OpenSSL RAND_pseudo_bytes() function does not automatically reseed
   its RNG on fork(), two child processes (with the same pid) generate the same
   random numbers: see issue #18747. Kernel RNGs don't have this issue,
   they have access to good quality entropy sources.

   If raise is zero:

   - Don't raise an exception on error
   - Don't call the Python signal handler (don't call PyErr_CheckSignals()) if
     a function fails with EINTR: retry directly the interrupted function
   - Don't release the GIL to call functions.
*/
static int
pyurandom(void *buffer, Py_ssize_t size, int blocking, int raise)
{
#if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)
    int res;
#endif

    if (size < 0) {
        if (raise) {
            PyErr_Format(PyExc_ValueError,
                         "negative argument not allowed");
        }
        return -1;
    }

    if (size == 0) {
        return 0;
    }

#ifdef MS_WINDOWS
    return win32_urandom((unsigned char *)buffer, size, raise);
#else

#if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)
    if (HAVE_GETENTRYPY_GETRANDOM_RUNTIME) {
#ifdef PY_GETRANDOM
        res = py_getrandom(buffer, size, blocking, raise);
#else
        res = py_getentropy(buffer, size, raise);
#endif
        if (res < 0) {
            return -1;
        }
        if (res == 1) {
            return 0;
        }
        /* getrandom() or getentropy() function is not available: failed with
           ENOSYS or EPERM. Fall back on reading from /dev/urandom. */
        } /* end of availability block */
#endif

    return dev_urandom(buffer, size, raise);
#endif
}

/* Fill buffer with size pseudo-random bytes from the operating system random
   number generator (RNG). It is suitable for most cryptographic purposes
   except long living private keys for asymmetric encryption.

   On Linux 3.17 and newer, the getrandom() syscall is used in blocking mode:
   block until the system urandom entropy pool is initialized (128 bits are
   collected by the kernel).

   Return 0 on success. Raise an exception and return -1 on error. */
int
_PyOS_URandom(void *buffer, Py_ssize_t size)
{
    return pyurandom(buffer, size, 1, 1);
}

/* Fill buffer with size pseudo-random bytes from the operating system random
   number generator (RNG). It is not suitable for cryptographic purpose.

   On Linux 3.17 and newer (when getrandom() syscall is used), if the system
   urandom is not initialized yet, the function returns "weak" entropy read
   from /dev/urandom.

   Return 0 on success. Raise an exception and return -1 on error. */
int
_PyOS_URandomNonblock(void *buffer, Py_ssize_t size)
{
    return pyurandom(buffer, size, 0, 1);
}


PyStatus
_Py_HashRandomization_Init(const PyConfig *config)
{
    void *secret = &_Py_HashSecret;
    Py_ssize_t secret_size = sizeof(_Py_HashSecret_t);

    if (_Py_HashSecret_Initialized) {
        return _PyStatus_OK();
    }
    _Py_HashSecret_Initialized = 1;

    if (config->use_hash_seed) {
        if (config->hash_seed == 0) {
            /* disable the randomized hash */
            memset(secret, 0, secret_size);
        }
        else {
            /* use the specified hash seed */
            lcg_urandom(config->hash_seed, secret, secret_size);
        }
    }
    else {
        /* use a random hash seed */
        int res;

        /* _PyRandom_Init() is called very early in the Python initialization
           and so exceptions cannot be used (use raise=0).

           _PyRandom_Init() must not block Python initialization: call
           pyurandom() is non-blocking mode (blocking=0): see the PEP 524. */
        res = pyurandom(secret, secret_size, 0, 0);
        if (res < 0) {
            return _PyStatus_ERR("failed to get random numbers "
                                 "to initialize Python");
        }
    }
    return _PyStatus_OK();
}


void
_Py_HashRandomization_Fini(void)
{
#ifndef MS_WINDOWS
    dev_urandom_close();
#endif
}

Coverage Report

Created: 2022-07-08 09:39

Line	Count	Source (jump to first uncovered line)
1	#include "Python.h"
2	#include "pycore_initconfig.h"
3	#include "pycore_fileutils.h" // _Py_fstat_noraise()
4
5	#ifdef MS_WINDOWS
6	# include <windows.h>
7	# include <bcrypt.h>
8	#else
9	# include <fcntl.h>
10	# ifdef HAVE_SYS_STAT_H
11	# include <sys/stat.h>
12	# endif
13	# ifdef HAVE_LINUX_RANDOM_H
14	# include <linux/random.h>
15	# endif
16	# if defined(HAVE_SYS_RANDOM_H) && (defined(HAVE_GETRANDOM) \|\| defined(HAVE_GETENTROPY))
17	# include <sys/random.h>
18	# endif
19	# if !defined(HAVE_GETRANDOM) && defined(HAVE_GETRANDOM_SYSCALL)
20	# include <sys/syscall.h>
21	# endif
22	#endif
23
24	#ifdef _Py_MEMORY_SANITIZER
25	# include <sanitizer/msan_interface.h>
26	#endif
27
28	#if defined(__APPLE__) && defined(__has_builtin)
29	# if __has_builtin(__builtin_available)
30	# define HAVE_GETENTRYPY_GETRANDOM_RUNTIME __builtin_available(macOS 10.12, iOS 10.10, tvOS 10.0, watchOS 3.0, *)
31	# endif
32	#endif
33	#ifndef HAVE_GETENTRYPY_GETRANDOM_RUNTIME
34	# define HAVE_GETENTRYPY_GETRANDOM_RUNTIME 1
35	#endif
36
37
38	#ifdef Py_DEBUG
39	int _Py_HashSecret_Initialized = 0;
40	#else
41	static int _Py_HashSecret_Initialized = 0;
42	#endif
43
44	#ifdef MS_WINDOWS
45
46	/* Fill buffer with size pseudo-random bytes generated by the Windows CryptoGen
47	API. Return 0 on success, or raise an exception and return -1 on error. */
48	static int
49	win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
50	{
51	while (size > 0)
52	{
53	DWORD chunk = (DWORD)Py_MIN(size, PY_DWORD_MAX);
54	NTSTATUS status = BCryptGenRandom(NULL, buffer, chunk, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
55	if (!BCRYPT_SUCCESS(status)) {
56	/* BCryptGenRandom() failed */
57	if (raise) {
58	PyErr_SetFromWindowsErr(0);
59	}
60	return -1;
61	}
62	buffer += chunk;
63	size -= chunk;
64	}
65	return 0;
66	}
67
68	#else /* !MS_WINDOWS */
69
70	#if defined(HAVE_GETRANDOM) \|\| defined(HAVE_GETRANDOM_SYSCALL)
71	#define PY_GETRANDOM 1
72
73	/* Call getrandom() to get random bytes:
74
75	- Return 1 on success
76	- Return 0 if getrandom() is not available (failed with ENOSYS or EPERM),
77	or if getrandom(GRND_NONBLOCK) failed with EAGAIN (system urandom not
78	initialized yet) and raise=0.
79	- Raise an exception (if raise is non-zero) and return -1 on error:
80	if getrandom() failed with EINTR, raise is non-zero and the Python signal
81	handler raised an exception, or if getrandom() failed with a different
82	error.
83
84	getrandom() is retried if it failed with EINTR: interrupted by a signal. */
85	static int
86	py_getrandom(void *buffer, Py_ssize_t size, int blocking, int raise)
87	{
88	/* Is getrandom() supported by the running kernel? Set to 0 if getrandom()
89	failed with ENOSYS or EPERM. Need Linux kernel 3.17 or newer, or Solaris
90	11.3 or newer */
91	static int getrandom_works = 1;
92	int flags;
93	char *dest;
94	long n;
95
96	if (!getrandom_works) { Branch (96:9): [True: 0, False: 166k]
97	return 0;
98	}
99
100	flags = blocking ? 0166k : GRND_NONBLOCK; Branch (100:13): [True: 166k, False: 143]
101	dest = buffer;
102	while (0 < size) { Branch (102:12): [True: 166k, False: 166k]
103	#if defined(__sun) && defined(__SVR4)
104	/* Issue #26735: On Solaris, getrandom() is limited to returning up
105	to 1024 bytes. Call it multiple times if more bytes are
106	requested. */
107	n = Py_MIN(size, 1024);
108	#else
109	n = Py_MIN(size, LONG_MAX);
110	#endif
111
112	errno = 0;
113	#ifdef HAVE_GETRANDOM
114	if (raise) { Branch (114:13): [True: 166k, False: 70]
115	Py_BEGIN_ALLOW_THREADS
116	n = getrandom(dest, n, flags);
117	Py_END_ALLOW_THREADS
118	}
119	else {
120	n = getrandom(dest, n, flags);
121	}
122	#else
123	/* On Linux, use the syscall() function because the GNU libc doesn't
124	expose the Linux getrandom() syscall yet. See:
125	https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */
126	if (raise) {
127	Py_BEGIN_ALLOW_THREADS
128	n = syscall(SYS_getrandom, dest, n, flags);
129	Py_END_ALLOW_THREADS
130	}
131	else {
132	n = syscall(SYS_getrandom, dest, n, flags);
133	}
134	# ifdef _Py_MEMORY_SANITIZER
135	if (n > 0) {
136	__msan_unpoison(dest, n);
137	}
138	# endif
139	#endif
140
141	if (n < 0) { Branch (141:13): [True: 0, False: 166k]
142	/* ENOSYS: the syscall is not supported by the kernel.
143	EPERM: the syscall is blocked by a security policy (ex: SECCOMP)
144	or something else. */
145	if (errno == ENOSYS \|\| errno == EPERM) { Branch (145:17): [True: 0, False: 0] Branch (145:36): [True: 0, False: 0]
146	getrandom_works = 0;
147	return 0;
148	}
149
150	/* getrandom(GRND_NONBLOCK) fails with EAGAIN if the system urandom
151	is not initialized yet. For _PyRandom_Init(), we ignore the
152	error and fall back on reading /dev/urandom which never blocks,
153	even if the system urandom is not initialized yet:
154	see the PEP 524. */
155	if (errno == EAGAIN && !raise && !blocking) { Branch (155:17): [True: 0, False: 0] Branch (155:36): [True: 0, False: 0] Branch (155:46): [True: 0, False: 0]
156	return 0;
157	}
158
159	if (errno == EINTR) { Branch (159:17): [True: 0, False: 0]
160	if (raise) { Branch (160:21): [True: 0, False: 0]
161	if (PyErr_CheckSignals()) { Branch (161:25): [True: 0, False: 0]
162	return -1;
163	}
164	}
165
166	/* retry getrandom() if it was interrupted by a signal */
167	continue;
168	}
169
170	if (raise) { Branch (170:17): [True: 0, False: 0]
171	PyErr_SetFromErrno(PyExc_OSError);
172	}
173	return -1;
174	}
175
176	dest += n;
177	size -= n;
178	}
179	return 1;
180	}
181
182	#elif defined(HAVE_GETENTROPY)
183	#define PY_GETENTROPY 1
184
185	/* Fill buffer with size pseudo-random bytes generated by getentropy():
186
187	- Return 1 on success
188	- Return 0 if getentropy() syscall is not available (failed with ENOSYS or
189	EPERM).
190	- Raise an exception (if raise is non-zero) and return -1 on error:
191	if getentropy() failed with EINTR, raise is non-zero and the Python signal
192	handler raised an exception, or if getentropy() failed with a different
193	error.
194
195	getentropy() is retried if it failed with EINTR: interrupted by a signal. */
196
197	#if defined(__APPLE__) && defined(__has_attribute) && __has_attribute(availability)
198	static int
199	py_getentropy(char *buffer, Py_ssize_t size, int raise)
200	__attribute__((availability(macos,introduced=10.12)))
201	__attribute__((availability(ios,introduced=10.0)))
202	__attribute__((availability(tvos,introduced=10.0)))
203	__attribute__((availability(watchos,introduced=3.0)));
204	#endif
205
206	static int
207	py_getentropy(char *buffer, Py_ssize_t size, int raise)
208	{
209	/* Is getentropy() supported by the running kernel? Set to 0 if
210	getentropy() failed with ENOSYS or EPERM. */
211	static int getentropy_works = 1;
212
213	if (!getentropy_works) {
214	return 0;
215	}
216
217	while (size > 0) {
218	/* getentropy() is limited to returning up to 256 bytes. Call it
219	multiple times if more bytes are requested. */
220	Py_ssize_t len = Py_MIN(size, 256);
221	int res;
222
223	if (raise) {
224	Py_BEGIN_ALLOW_THREADS
225	res = getentropy(buffer, len);
226	Py_END_ALLOW_THREADS
227	}
228	else {
229	res = getentropy(buffer, len);
230	}
231
232	if (res < 0) {
233	/* ENOSYS: the syscall is not supported by the running kernel.
234	EPERM: the syscall is blocked by a security policy (ex: SECCOMP)
235	or something else. */
236	if (errno == ENOSYS \|\| errno == EPERM) {
237	getentropy_works = 0;
238	return 0;
239	}
240
241	if (errno == EINTR) {
242	if (raise) {
243	if (PyErr_CheckSignals()) {
244	return -1;
245	}
246	}
247
248	/* retry getentropy() if it was interrupted by a signal */
249	continue;
250	}
251
252	if (raise) {
253	PyErr_SetFromErrno(PyExc_OSError);
254	}
255	return -1;
256	}
257
258	buffer += len;
259	size -= len;
260	}
261	return 1;
262	}
263	#endif /* defined(HAVE_GETENTROPY) && !(defined(__sun) && defined(__SVR4)) */
264
265
266	static struct {
267	int fd;
268	dev_t st_dev;
269	ino_t st_ino;
270	} urandom_cache = { -1 };
271
272	/* Read random bytes from the /dev/urandom device:
273
274	- Return 0 on success
275	- Raise an exception (if raise is non-zero) and return -1 on error
276
277	Possible causes of errors:
278
279	- open() failed with ENOENT, ENXIO, ENODEV, EACCES: the /dev/urandom device
280	was not found. For example, it was removed manually or not exposed in a
281	chroot or container.
282	- open() failed with a different error
283	- fstat() failed
284	- read() failed or returned 0
285
286	read() is retried if it failed with EINTR: interrupted by a signal.
287
288	The file descriptor of the device is kept open between calls to avoid using
289	many file descriptors when run in parallel from multiple threads:
290	see the issue #18756.
291
292	st_dev and st_ino fields of the file descriptor (from fstat()) are cached to
293	check if the file descriptor was replaced by a different file (which is
294	likely a bug in the application): see the issue #21207.
295
296	If the file descriptor was closed or replaced, open a new file descriptor
297	but don't close the old file descriptor: it probably points to something
298	important for some third-party code. */
299	static int
300	dev_urandom(char *buffer, Py_ssize_t size, int raise)
301	{
302	int fd;
303	Py_ssize_t n;
304
305	if (raise) { Branch (305:9): [True: 0, False: 0]
306	struct _Py_stat_struct st;
307	int fstat_result;
308
309	if (urandom_cache.fd >= 0) { Branch (309:13): [True: 0, False: 0]
310	Py_BEGIN_ALLOW_THREADS
311	fstat_result = _Py_fstat_noraise(urandom_cache.fd, &st);
312	Py_END_ALLOW_THREADS
313
314	/* Does the fd point to the same thing as before? (issue #21207) */
315	if (fstat_result Branch (315:17): [True: 0, False: 0]
316	\|\| st.st_dev != urandom_cache.st_dev Branch (316:20): [True: 0, False: 0]
317	\|\| st.st_ino != urandom_cache.st_ino) { Branch (317:20): [True: 0, False: 0]
318	/* Something changed: forget the cached fd (but don't close it,
319	since it probably points to something important for some
320	third-party code). */
321	urandom_cache.fd = -1;
322	}
323	}
324	if (urandom_cache.fd >= 0) Branch (324:13): [True: 0, False: 0]
325	fd = urandom_cache.fd;
326	else {
327	fd = _Py_open("/dev/urandom", O_RDONLY);
328	if (fd < 0) { Branch (328:17): [True: 0, False: 0]
329	if (errno == ENOENT \|\| errno == ENXIO \|\| Branch (329:21): [True: 0, False: 0] Branch (329:40): [True: 0, False: 0]
330	errno == ENODEV \|\| errno == EACCES) { Branch (330:21): [True: 0, False: 0] Branch (330:40): [True: 0, False: 0]
331	PyErr_SetString(PyExc_NotImplementedError,
332	"/dev/urandom (or equivalent) not found");
333	}
334	/* otherwise, keep the OSError exception raised by _Py_open() */
335	return -1;
336	}
337	if (urandom_cache.fd >= 0) { Branch (337:17): [True: 0, False: 0]
338	/* urandom_fd was initialized by another thread while we were
339	not holding the GIL, keep it. */
340	close(fd);
341	fd = urandom_cache.fd;
342	}
343	else {
344	if (_Py_fstat(fd, &st)) { Branch (344:21): [True: 0, False: 0]
345	close(fd);
346	return -1;
347	}
348	else {
349	urandom_cache.fd = fd;
350	urandom_cache.st_dev = st.st_dev;
351	urandom_cache.st_ino = st.st_ino;
352	}
353	}
354	}
355
356	do {
357	n = _Py_read(fd, buffer, (size_t)size);
358	if (n == -1) Branch (358:17): [True: 0, False: 0]
359	return -1;
360	if (n == 0) { Branch (360:17): [True: 0, False: 0]
361	PyErr_Format(PyExc_RuntimeError,
362	"Failed to read %zi bytes from /dev/urandom",
363	size);
364	return -1;
365	}
366
367	buffer += n;
368	size -= n;
369	} while (0 < size); Branch (369:18): [True: 0, False: 0]
370	}
371	else {
372	fd = _Py_open_noraise("/dev/urandom", O_RDONLY);
373	if (fd < 0) { Branch (373:13): [True: 0, False: 0]
374	return -1;
375	}
376
377	while (0 < size) Branch (377:16): [True: 0, False: 0]
378	{
379	do {
380	n = read(fd, buffer, (size_t)size);
381	} while (n < 0 && errno == EINTR); Branch (381:22): [True: 0, False: 0] Branch (381:31): [True: 0, False: 0]
382
383	if (n <= 0) { Branch (383:17): [True: 0, False: 0]
384	/* stop on error or if read(size) returned 0 */
385	close(fd);
386	return -1;
387	}
388
389	buffer += n;
390	size -= n;
391	}
392	close(fd);
393	}
394	return 0;
395	}
396
397	static void
398	dev_urandom_close(void)
399	{
400	if (urandom_cache.fd >= 0) { Branch (400:9): [True: 0, False: 103]
401	close(urandom_cache.fd);
402	urandom_cache.fd = -1;
403	}
404	}
405	#endif /* !MS_WINDOWS */
406
407
408	/* Fill buffer with pseudo-random bytes generated by a linear congruent
409	generator (LCG):
410
411	x(n+1) = (x(n) * 214013 + 2531011) % 2^32
412
413	Use bits 23..16 of x(n) to generate a byte. */
414	static void
415	lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size)
416	{
417	size_t index;
418	unsigned int x;
419
420	x = x0;
421	for (index=0; index < size; index++72 ) { Branch (421:19): [True: 72, False: 3]
422	x *= 214013;
423	x += 2531011;
424	/* modulo 2 ^ (8 * sizeof(int)) */
425	buffer[index] = (x >> 16) & 0xff;
426	}
427	}
428
429	/* Read random bytes:
430
431	- Return 0 on success
432	- Raise an exception (if raise is non-zero) and return -1 on error
433
434	Used sources of entropy ordered by preference, preferred source first:
435
436	- BCryptGenRandom() on Windows
437	- getrandom() function (ex: Linux and Solaris): call py_getrandom()
438	- getentropy() function (ex: OpenBSD): call py_getentropy()
439	- /dev/urandom device
440
441	Read from the /dev/urandom device if getrandom() or getentropy() function
442	is not available or does not work.
443
444	Prefer getrandom() over getentropy() because getrandom() supports blocking
445	and non-blocking mode: see the PEP 524. Python requires non-blocking RNG at
446	startup to initialize its hash secret, but os.urandom() must block until the
447	system urandom is initialized (at least on Linux 3.17 and newer).
448
449	Prefer getrandom() and getentropy() over reading directly /dev/urandom
450	because these functions don't need file descriptors and so avoid ENFILE or
451	EMFILE errors (too many open files): see the issue #18756.
452
453	Only the getrandom() function supports non-blocking mode.
454
455	Only use RNG running in the kernel. They are more secure because it is
456	harder to get the internal state of a RNG running in the kernel land than a
457	RNG running in the user land. The kernel has a direct access to the hardware
458	and has access to hardware RNG, they are used as entropy sources.
459
460	Note: the OpenSSL RAND_pseudo_bytes() function does not automatically reseed
461	its RNG on fork(), two child processes (with the same pid) generate the same
462	random numbers: see issue #18747. Kernel RNGs don't have this issue,
463	they have access to good quality entropy sources.
464
465	If raise is zero:
466
467	- Don't raise an exception on error
468	- Don't call the Python signal handler (don't call PyErr_CheckSignals()) if
469	a function fails with EINTR: retry directly the interrupted function
470	- Don't release the GIL to call functions.
471	*/
472	static int
473	pyurandom(void *buffer, Py_ssize_t size, int blocking, int raise)
474	{
475	#if defined(PY_GETRANDOM) \|\| defined(PY_GETENTROPY)
476	int res;
477	#endif
478
479	if (size < 0) { Branch (479:9): [True: 0, False: 166k]
480	if (raise) { Branch (480:13): [True: 0, False: 0]
481	PyErr_Format(PyExc_ValueError,
482	"negative argument not allowed");
483	}
484	return -1;
485	}
486
487	if (size == 0) { Branch (487:9): [True: 3, False: 166k]
488	return 0;
489	}
490
491	#ifdef MS_WINDOWS
492	return win32_urandom((unsigned char *)buffer, size, raise);
493	#else
494
495	#if defined(PY_GETRANDOM) \|\| defined(PY_GETENTROPY)
496	if (HAVE_GETENTRYPY_GETRANDOM_RUNTIME) {
497	#ifdef PY_GETRANDOM
498	res = py_getrandom(buffer, size, blocking, raise);
499	#else
500	res = py_getentropy(buffer, size, raise);
501	#endif
502	if (res < 0) { Branch (502:13): [True: 0, False: 166k]
503	return -1;
504	}
505	if (res == 1) { Branch (505:13): [True: 166k, False: 0]
506	return 0;
507	}
508	/* getrandom() or getentropy() function is not available: failed with
509	ENOSYS or EPERM. Fall back on reading from /dev/urandom. */
510	} /* end of availability block */
511	#endif
512
513	return dev_urandom(buffer, size, raise);
514	#endif
515	}
516
517	/* Fill buffer with size pseudo-random bytes from the operating system random
518	number generator (RNG). It is suitable for most cryptographic purposes
519	except long living private keys for asymmetric encryption.
520
521	On Linux 3.17 and newer, the getrandom() syscall is used in blocking mode:
522	block until the system urandom entropy pool is initialized (128 bits are
523	collected by the kernel).
524
525	Return 0 on success. Raise an exception and return -1 on error. */
526	int
527	_PyOS_URandom(void *buffer, Py_ssize_t size)
528	{
529	return pyurandom(buffer, size, 1, 1);
530	}
531
532	/* Fill buffer with size pseudo-random bytes from the operating system random
533	number generator (RNG). It is not suitable for cryptographic purpose.
534
535	On Linux 3.17 and newer (when getrandom() syscall is used), if the system
536	urandom is not initialized yet, the function returns "weak" entropy read
537	from /dev/urandom.
538
539	Return 0 on success. Raise an exception and return -1 on error. */
540	int
541	_PyOS_URandomNonblock(void *buffer, Py_ssize_t size)
542	{
543	return pyurandom(buffer, size, 0, 1);
544	}
545
546
547	PyStatus
548	_Py_HashRandomization_Init(const PyConfig *config)
549	{
550	void *secret = &_Py_HashSecret;
551	Py_ssize_t secret_size = sizeof(_Py_HashSecret_t);
552
553	if (_Py_HashSecret_Initialized) { Branch (553:9): [True: 34, False: 73]
554	return _PyStatus_OK();
555	}
556	_Py_HashSecret_Initialized = 1;
557
558	if (config->use_hash_seed) { Branch (558:9): [True: 3, False: 70]
559	if (config->hash_seed == 0) { Branch (559:13): [True: 0, False: 3]
560	/* disable the randomized hash */
561	memset(secret, 0, secret_size);
562	}
563	else {
564	/* use the specified hash seed */
565	lcg_urandom(config->hash_seed, secret, secret_size);
566	}
567	}
568	else {
569	/* use a random hash seed */
570	int res;
571
572	/* _PyRandom_Init() is called very early in the Python initialization
573	and so exceptions cannot be used (use raise=0).
574
575	_PyRandom_Init() must not block Python initialization: call
576	pyurandom() is non-blocking mode (blocking=0): see the PEP 524. */
577	res = pyurandom(secret, secret_size, 0, 0);
578	if (res < 0) { Branch (578:13): [True: 0, False: 70]
579	return _PyStatus_ERR("failed to get random numbers "
580	"to initialize Python");
581	}
582	}
583	return _PyStatus_OK();
584	}
585
586
587	void
588	_Py_HashRandomization_Fini(void)
589	{
590	#ifndef MS_WINDOWS
591	dev_urandom_close();
592	#endif
593	}