New osrandom_engine in C (#3229)

* New osrandom_engine in C

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

Signed-off-by: Christian Heimes <christian@python.org>

* osrandom_engine

* Fix naming bug caused by search 'n replace mistake
* Make it easier to override osrandom auto-detection
* Add engine ctrl and backend API to get implementation from ENGINE

Signed-off-by: Christian Heimes <christian@python.org>

* Better test coverage, documentation, LICENSE

Signed-off-by: Christian Heimes <christian@python.org>

* Coverage is hard.

Signed-off-by: Christian Heimes <christian@python.org>

* * enable win32 check
* read() returns size_t

Signed-off-by: Christian Heimes <christian@python.org>

* Add macOS to spelling list. Remove dead code from header file.

Signed-off-by: Christian Heimes <christian@python.org>

* remove CCRandomGenerateBytes path and update getentropy to work on macOS

This change allows us to test all the engines in our CI:
* getentropy (tested by macOS sierra)
* getrandom (tested on several linux builders)
* /dev/urandom (tested on FreeBSD, OS X 10.11 and below, & older linux)
* CryptGenRandom (tested on windows builders)

I also fixed bugs preventing compilation in the getentropy code

* getentropy() returns int and is restricted to 256 bytes on macOS, too.

Signed-off-by: Christian Heimes <christian@python.org>

* add versionadded

* Re-add import of os module

* Fixes related to Alex's recent review.

Signed-off-by: Christian Heimes <christian@python.org>

* 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 <christian@python.org>

1 files changed, 88 insertions, 0 deletions

diff --git a/src/_cffi_src/openssl/src/osrandom_engine.h b/src/_cffi_src/openssl/src/osrandom_engine.h
new file mode 100644
index 00000000..d28ebf39
--- /dev/null
+++ b/src/_cffi_src/openssl/src/osrandom_engine.h
@@ -0,0 +1,88 @@
+#ifdef _WIN32
+  #include <Wincrypt.h>
+#else
+  #include <fcntl.h>
+  #include <unistd.h>
+   /* for defined(BSD) */
+  #include <sys/param.h>
+
+  #ifdef BSD
+    /* for SYS_getentropy */
+    #include <sys/syscall.h>
+  #endif
+
+  #ifdef __APPLE__
+    #include <sys/random.h>
+  #endif
+
+  #ifdef __linux__
+    /* for SYS_getrandom */
+    #include <sys/syscall.h>
+    #ifndef GRND_NONBLOCK
+      #define GRND_NONBLOCK 0x0001
+    #endif /* GRND_NONBLOCK */
+  #endif /* __linux__ */
+#endif /* _WIN32 */
+
+#define CRYPTOGRAPHY_OSRANDOM_ENGINE_CRYPTGENRANDOM 1
+#define CRYPTOGRAPHY_OSRANDOM_ENGINE_GETENTROPY 2
+#define CRYPTOGRAPHY_OSRANDOM_ENGINE_GETRANDOM 3
+#define CRYPTOGRAPHY_OSRANDOM_ENGINE_DEV_URANDOM 4
+
+#ifndef CRYPTOGRAPHY_OSRANDOM_ENGINE
+  #if defined(_WIN32)
+    /* Windows */
+    #define CRYPTOGRAPHY_OSRANDOM_ENGINE CRYPTOGRAPHY_OSRANDOM_ENGINE_CRYPTGENRANDOM
+  #elif defined(BSD) && defined(SYS_getentropy)
+    /* OpenBSD 5.6+ or macOS 10.12+ */
+    #define CRYPTOGRAPHY_OSRANDOM_ENGINE CRYPTOGRAPHY_OSRANDOM_ENGINE_GETENTROPY
+  #elif defined(__linux__) && defined(SYS_getrandom)
+    /* Linux 3.4.17+ */
+    #define CRYPTOGRAPHY_OSRANDOM_ENGINE CRYPTOGRAPHY_OSRANDOM_ENGINE_GETRANDOM
+  #else
+    /* Keep this as last entry, fall back to /dev/urandom */
+    #define CRYPTOGRAPHY_OSRANDOM_ENGINE CRYPTOGRAPHY_OSRANDOM_ENGINE_DEV_URANDOM
+  #endif
+#endif /* CRYPTOGRAPHY_OSRANDOM_ENGINE */
+
+/* Fallbacks need /dev/urandom helper functions. */
+#if CRYPTOGRAPHY_OSRANDOM_ENGINE == CRYPTOGRAPHY_OSRANDOM_ENGINE_GETRANDOM || \
+     CRYPTOGRAPHY_OSRANDOM_ENGINE == CRYPTOGRAPHY_OSRANDOM_ENGINE_DEV_URANDOM
+  #define CRYPTOGRAPHY_OSRANDOM_NEEDS_DEV_URANDOM 1
+#endif
+
+enum {
+    CRYPTOGRAPHY_OSRANDOM_GETRANDOM_INIT_FAILED = -2,
+    CRYPTOGRAPHY_OSRANDOM_GETRANDOM_NOT_INIT,
+    CRYPTOGRAPHY_OSRANDOM_GETRANDOM_FALLBACK,
+    CRYPTOGRAPHY_OSRANDOM_GETRANDOM_WORKS
+};
+
+/* engine ctrl */
+#define CRYPTOGRAPHY_OSRANDOM_GET_IMPLEMENTATION ENGINE_CMD_BASE
+
+/* error reporting */
+static void ERR_load_Cryptography_OSRandom_strings(void);
+static void ERR_Cryptography_OSRandom_error(int function, int reason,
+                                            char *file, int line);
+
+#define CRYPTOGRAPHY_OSRANDOM_F_INIT 100
+#define CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES 101
+#define CRYPTOGRAPHY_OSRANDOM_F_FINISH 102
+#define CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_FD 300
+#define CRYPTOGRAPHY_OSRANDOM_F_DEV_URANDOM_READ 301
+
+#define CRYPTOGRAPHY_OSRANDOM_R_CRYPTACQUIRECONTEXT 100
+#define CRYPTOGRAPHY_OSRANDOM_R_CRYPTGENRANDOM 101
+#define CRYPTOGRAPHY_OSRANDOM_R_CRYPTRELEASECONTEXT 102
+
+#define CRYPTOGRAPHY_OSRANDOM_R_GETENTROPY_FAILED 200
+
+#define CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_OPEN_FAILED 300
+#define CRYPTOGRAPHY_OSRANDOM_R_DEV_URANDOM_READ_FAILED 301
+
+#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED 400
+#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_EAGAIN 401
+#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_INIT_FAILED_UNEXPECTED 402
+#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_FAILED 403
+#define CRYPTOGRAPHY_OSRANDOM_R_GETRANDOM_NOT_INIT 404