New osrandom_engine in C (WIP)

Inspired by Python/random.c and the old implementation.

Signed-off-by: Christian Heimes <[email protected]>

src/_cffi_src/build_openssl.py

@@ -68,6 +68,7 @@ def _osx_libraries(build_static):
         "objects",
         "ocsp",
         "opensslv",
+        "osrandom_engine",
         "pem",
         "pkcs12",
         "rand",

src/_cffi_src/openssl/osrandom_engine.py

@@ -0,0 +1,29 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+from __future__ import absolute_import, division, print_function
+
+import os
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+
+with open(os.path.join(HERE, "src/osrandom_engine.h")) as f:
+    INCLUDES = f.read()
+
+TYPES = """
+static const char *const Cryptography_osrandom_engine_name;
+static const char *const Cryptography_osrandom_engine_id;
+"""
+
+FUNCTIONS = """
+int Cryptography_add_osrandom_engine(void);
+"""
+
+MACROS = """
+"""
+
+with open(os.path.join(HERE, "src/osrandom_engine.c")) as f:
+    CUSTOMIZATIONS = f.read()
+
+CONDITIONAL_NAMES = {}

src/_cffi_src/openssl/src/osrandom_engine.c

@@ -0,0 +1,350 @@
+/* Largely inspired by Python/random.c and the old implementation of osrandom_engine.c */
+
+static const char *Cryptography_osrandom_engine_id = "osrandom";
+static const char *Cryptography_osrandom_engine_name = CRYPTOGRAPHY_OSRANDOM_ENGINE_NAME;
+
+/****************************************************************************
+ * Windows
+ */
+#if defined(_WIN32)
+#define RANDOM_ENGINE 1
+
+static HCRYPTPROV hCryptProv = 0;
+
+static int osrandom_init(ENGINE *e) {
+    if (hCryptProv != 0) {
+        return 1;
+    }
+    if (CryptAcquireContext(&hCryptProv, NULL, NULL,
+                            PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+static int osrandom_rand_bytes(unsigned char *buffer, int size) {
+    if (hCryptProv == 0) {
+        return 0;
+    }
+
+    if (!CryptGenRandom(hCryptProv, (DWORD)size, buffer)) {
+        ERR_put_error(
+            ERR_LIB_RAND, 0, ERR_R_RAND_LIB,
+            "osrandom_engine.py:CryptGenRandom()", 0
+        );
+        return 0;
+    }
+    return 1;
+}
+
+static int osrandom_finish(ENGINE *e) {
+    if (CryptReleaseContext(hCryptProv, 0)) {
+        hCryptProv = 0;
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+static int osrandom_rand_status(void) {
+    if (hCryptProv == 0) {
+        return 0;
+    } else {
+        return 1;
+    }
+}
+#elif defined(CRYPTOGRAPHY_HAVE_GETENTROPY)
+
+/****************************************************************************
+ * BSD getentropy
+ */
+static int osrandom_init(ENGINE *e) {
+    return 1;
+}
+
+static int osrandom_rand_bytes(unsigned char *buffer, int size) {
+    Py_ssize_t len;
+    int res;
+    while (size > 0) {
+        len = size > 256 : 256: size;
+        res = getentropy(buffer, len);
+        if (res < 0) {
+            ERR_put_error(
+                ERR_LIB_RAND, 0, ERR_R_RAND_LIB,
+                "osrandom_engine.py:getentropy()", 0
+            );
+            return 0;
+        }
+        buffer += len;
+        size -= len;
+    }
+    return 1;
+}
+
+static int osrandom_finish(ENGINE *e) {
+    return 1;
+}
+
+static int osrandom_rand_status(void) {
+    return 1;
+}
+
+#else /* not _WIN32 and not BSD CRYPTOGRAPHY_HAVE_GETENTROPY */
+
+/****************************************************************************
+ * /dev/urandom helpers for all non-BSD Unix platforms
+ */
+
+static struct {
+    int fd;
+    dev_t st_dev;
+    ino_t st_ino;
+} urandom_cache = { -1 };
+
+/* return -1 on error */
+static int dev_urandom_fd(void) {
+    int fd, n, flags;
+    struct stat st;
+
+    /* Check that fd still points to the correct device */
+    if (urandom_cache.fd >= 0) {
+        if (fstat(urandom_cache.fd, &st)
+                || st.st_dev != urandom_cache.st_dev
+                || st.st_ino != urandom_cache.st_ino) {
+            urandom_cache.fd = -1;
+        }
+    }
+    if (urandom_cache.fd < 0) {
+        fd = open("/dev/urandom", O_RDONLY);
+        if (fd < 0) {
+            goto error;
+        }
+        if (fstat(fd, &st)) {
+            goto error;
+        }
+        /* Another thread initialized the fd */
+        if (urandom_cache.fd >= 0) {
+            do {
+                n = close(fd);
+            } while (n < 0 && errno == EINTR);
+            return urandom_cache.fd;
+        }
+        flags = fcntl(fd, F_GETFD);
+        if (flags == -1) {
+            goto error;
+        } else if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
+            goto error;
+        }
+        urandom_cache.st_dev = st.st_dev;
+        urandom_cache.st_ino = st.st_ino;
+        urandom_cache.fd = fd;
+    }
+    return urandom_cache.fd;
+
+  error:
+    if (fd != -1) {
+        do {
+            n = close(fd);
+        } while (n < 0 && errno == EINTR);
+    }
+    ERR_put_error(
+        ERR_LIB_RAND, 0, ERR_R_RAND_LIB,
+        "osrandom_engine.py:dev_urandom_fd()", 0);
+    return -1;
+}
+
+static int dev_urandom_read(unsigned char *buffer, int size) {
+    int fd, n;
+
+    fd = dev_urandom_fd();
+    if (fd < 0) {
+        return 0;
+    }
+
+    while (size > 0) {
+        do {
+            n = read(fd, buffer, (size_t)size);
+        } while (n < 0 && errno == EINTR);
+
+        if (n <= 0) {
+            ERR_put_error(
+                ERR_LIB_RAND, 0, ERR_R_RAND_LIB,
+                "osrandom_engine.py:dev_urandom_read()", 0);
+            return 0;
+        }
+        buffer += n;
+        size -= n;
+    }
+    return 1;
+}
+
+static void dev_urandom_close(void) {
+    if (urandom_cache.fd >= 0) {
+        int fd, n;
+        struct stat st;
+
+        if (fstat(urandom_cache.fd, &st)
+                && st.st_dev == urandom_cache.st_dev
+                && st.st_ino == urandom_cache.st_ino) {
+            fd = urandom_cache.fd;
+            urandom_cache.fd = -1;
+            do {
+                n = close(fd);
+            } while (n < 0 && errno == EINTR);
+        }
+    }
+}
+
+/****************************************************************************
+ * Linux getrandom engine with fallback to dev_urandom
+ */
+
+#ifdef CRYPTOGRAPHY_HAVE_SYS_GETRANDOM
+static int getrandom_works = -1;
+
+static int osrandom_init(ENGINE *e) {
+    if (getrandom_works == -1) {
+        long n;
+        char dest[1];
+        n = syscall(SYS_getrandom, dest, sizeof(dest), GRND_NONBLOCK);
+        /* TODO: EAGAIN when Kernel RNG is not initialized. */
+        if (n < 0 && (errno == ENOSYS || errno == EPERM)) {
+            getrandom_works = 0;
+        } else {
+            getrandom_works = 1;
+        }
+    }
+    /* fallback to dev urandom */
+    if (getrandom_works == 0) {
+        int fd = dev_urandom_fd();
+        if (fd < 0) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+static int osrandom_rand_bytes(unsigned char *buffer, int size) {
+    if (getrandom_works == 1) {
+        long n;
+        while (size > 0) {
+            do {
+                n = syscall(SYS_getrandom, buffer, size, GRND_NONBLOCK);
+            } while (n < 0 && errno == EINTR);
+
+            if (n <= 0) {
+                ERR_put_error(
+                    ERR_LIB_RAND, 0, ERR_R_RAND_LIB,
+                    "osrandom_engine.py:SYS_getrandom", 0);
+                return 0;
+            }
+            buffer += n;
+            size -= n;
+        }
+        return 1;
+    } else {
+        return dev_urandom_read(buffer, size);
+    }
+}
+
+static int osrandom_finish(ENGINE *e) {
+    dev_urandom_close();
+    return 1;
+}
+
+static int osrandom_rand_status(void) {
+    if ((getrandom_works != 1) && (urandom_cache.fd < 0)) {
+        return 0;
+    }
+    return 1;
+}
+#endif /* CRYPTOGRAPHY_HAVE_SYS_GETRANDOM */
+
+/****************************************************************************
+ * dev_urandom engine for all remaining platforms
+ */
+
+#ifdef CRYPTOGRAPHY_USE_DEV_URANDOM
+
+static int osrandom_init(ENGINE *e) {
+    int fd = dev_urandom_fd();
+    if (fd < 0) {
+        return 0;
+    }
+    return 1;
+}
+
+static int osrandom_rand_bytes(unsigned char *buffer, int size) {
+    return dev_urandom_read(buffer, size);
+}
+
+static int osrandom_finish(ENGINE *e) {
+    dev_urandom_close();
+    return 1;
+}
+
+static int osrandom_rand_status(void) {
+    if (urandom_cache.fd < 0) {
+        return 0;
+    }
+    return 1;
+}
+
+#endif /* CRYPTOGRAPHY_USE_DEV_URANDOM */
+#endif /* _WIN32 */
+
+/* This replicates the behavior of the OpenSSL FIPS RNG, which returns a
+   -1 in the event that there is an error when calling RAND_pseudo_bytes. */
+static int osrandom_pseudo_rand_bytes(unsigned char *buffer, int size) {
+    int res = osrandom_rand_bytes(buffer, size);
+    if (res == 0) {
+        return -1;
+    } else {
+        return res;
+    }
+}
+
+static RAND_METHOD osrandom_rand = {
+    NULL,
+    osrandom_rand_bytes,
+    NULL,
+    NULL,
+    osrandom_pseudo_rand_bytes,
+    osrandom_rand_status,
+};
+
+/* Returns 1 if successfully added, 2 if engine has previously been added,
+   and 0 for error. */
+int Cryptography_add_osrandom_engine(void) {
+    ENGINE *e;
+    e = ENGINE_by_id(Cryptography_osrandom_engine_id);
+    if (e != NULL) {
+        ENGINE_free(e);
+        return 2;
+    } else {
+        ERR_clear_error();
+    }
+
+    e = ENGINE_new();
+    if (e == NULL) {
+        return 0;
+    }
+    if(!ENGINE_set_id(e, Cryptography_osrandom_engine_id) ||
+            !ENGINE_set_name(e, Cryptography_osrandom_engine_name) ||
+            !ENGINE_set_RAND(e, &osrandom_rand) ||
+            !ENGINE_set_init_function(e, osrandom_init) ||
+            !ENGINE_set_finish_function(e, osrandom_finish)) {
+        ENGINE_free(e);
+        return 0;
+    }
+    if (!ENGINE_add(e)) {
+        ENGINE_free(e);
+        return 0;
+    }
+    if (!ENGINE_free(e)) {
+        return 0;
+    }
+
+    return 1;
+}