bpo-22257: Small changes for PEP 432. (#1728)

PEP 432 specifies a number of large changes to interpreter startup code, including exposing a cleaner C-API. The major changes depend on a number of smaller changes. This patch includes all those smaller changes.

1 files changed, 629 insertions, 0 deletions

diff --git a/Python/bootstrap_hash.c b/Python/bootstrap_hash.c
new file mode 100644
index 0000000..27d26ea
--- /dev/null
+++ b/Python/bootstrap_hash.c
@@ -0,0 +1,629 @@
+#include "Python.h"
+#ifdef MS_WINDOWS
+#  include <windows.h>
+/* All sample MSDN wincrypt programs include the header below. It is at least
+ * required with Min GW. */
+#  include <wincrypt.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_DEBUG
+int _Py_HashSecret_Initialized = 0;
+#else
+static int _Py_HashSecret_Initialized = 0;
+#endif
+
+#ifdef MS_WINDOWS
+static HCRYPTPROV hCryptProv = 0;
+
+static int
+win32_urandom_init(int raise)
+{
+    /* Acquire context */
+    if (!CryptAcquireContext(&hCryptProv, NULL, NULL,
+                             PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
+        goto error;
+
+    return 0;
+
+error:
+    if (raise) {
+        PyErr_SetFromWindowsErr(0);
+    }
+    return -1;
+}
+
+/* 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)
+{
+    Py_ssize_t chunk;
+
+    if (hCryptProv == 0)
+    {
+        if (win32_urandom_init(raise) == -1) {
+            return -1;
+        }
+    }
+
+    while (size > 0)
+    {
+        chunk = size > INT_MAX ? INT_MAX : size;
+        if (!CryptGenRandom(hCryptProv, (DWORD)chunk, buffer))
+        {
+            /* CryptGenRandom() 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 ? 0 : GRND_NONBLOCK;
+    dest = buffer;
+    while (0 < size) {
+#ifdef sun
+        /* 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);
+        }
+#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 initialiazed 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. */
+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) */
+
+
+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;
+
+        if (urandom_cache.fd >= 0) {
+            /* Does the fd point to the same thing as before? (issue #21207) */
+            if (_Py_fstat_noraise(urandom_cache.fd, &st)
+                || 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++) {
+        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:
+
+   - CryptGenRandom() 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)
+#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. */
+#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);
+}
+
+int Py_ReadHashSeed(char *seed_text,
+                    int *use_hash_seed,
+                    unsigned long *hash_seed)
+{
+    Py_BUILD_ASSERT(sizeof(_Py_HashSecret_t) == sizeof(_Py_HashSecret.uc));
+    /* Convert a text seed to a numeric one */
+    if (seed_text && *seed_text != '\0' && strcmp(seed_text, "random") != 0) {
+        char *endptr = seed_text;
+        unsigned long seed;
+        seed = strtoul(seed_text, &endptr, 10);
+        if (*endptr != '\0'
+            || seed > 4294967295UL
+            || (errno == ERANGE && seed == ULONG_MAX))
+        {
+            return -1;
+        }
+        /* Use a specific hash */
+        *use_hash_seed = 1;
+        *hash_seed = seed;
+    }
+    else {
+        /* Use a random hash */
+        *use_hash_seed = 0;
+        *hash_seed = 0;
+    }
+    return 0;
+}
+
+static void
+init_hash_secret(int use_hash_seed,
+                 unsigned long hash_seed)
+{
+    void *secret = &_Py_HashSecret;
+    Py_ssize_t secret_size = sizeof(_Py_HashSecret_t);
+
+    if (_Py_HashSecret_Initialized)
+        return;
+    _Py_HashSecret_Initialized = 1;
+
+    if (use_hash_seed) {
+        if (hash_seed == 0) {
+            /* disable the randomized hash */
+            memset(secret, 0, secret_size);
+        }
+        else {
+            /* use the specified hash seed */
+            lcg_urandom(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) {
+            Py_FatalError("failed to get random numbers to initialize Python");
+        }
+    }
+}
+
+void
+_Py_HashRandomization_Init(void)
+{
+    char *seed_text;
+    int use_hash_seed = -1;
+    unsigned long hash_seed;
+
+    if (use_hash_seed < 0) {
+        seed_text = Py_GETENV("PYTHONHASHSEED");
+        if (Py_ReadHashSeed(seed_text, &use_hash_seed, &hash_seed) < 0) {
+            Py_FatalError("PYTHONHASHSEED must be \"random\" or an integer "
+                          "in range [0; 4294967295]");
+        }
+    }
+    init_hash_secret(use_hash_seed, hash_seed);
+}
+
+void
+_Py_HashRandomization_Fini(void)
+{
+#ifdef MS_WINDOWS
+    if (hCryptProv) {
+        CryptReleaseContext(hCryptProv, 0);
+        hCryptProv = 0;
+    }
+#else
+    dev_urandom_close();
+#endif
+}