Remove ability to independently select random number generator

Remove the ability to select random number generator independently from
SSL library. Instead, use the random number generator from the SSL
library (today only OpenSSL supported) if one is configured. If no SSL
library is configured, use the platform default (which means use
CryptoAPI on Win32 and /dev/urandom on Linux).

This also restructures pg_strong_random.c to have three clearly separate
sections, one for each implementation, with two functions in each,
instead of a scattered set of ifdefs throughout the whole file.

Author: Daniel Gustafsson, Magnus Hagander, Michael Paquier
Discussion: https://postgr.es/m/632623.1605460616@sss.pgh.pa.us

3 files changed, 83 insertions, 130 deletions

diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index fb270df678a..de8f838e536 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -862,9 +862,6 @@
 /* Define to 1 to build with BSD Authentication support. (--with-bsd-auth) */
 #undef USE_BSD_AUTH
 
-/* Define to use /dev/urandom for random number generation */
-#undef USE_DEV_URANDOM
-
 /* Define to build with ICU support. (--with-icu) */
 #undef USE_ICU
 
@@ -887,9 +884,6 @@
 /* Define to build with OpenSSL support. (--with-openssl) */
 #undef USE_OPENSSL
 
-/* Define to use OpenSSL for random number generation */
-#undef USE_OPENSSL_RANDOM
-
 /* Define to 1 to build with PAM support. (--with-pam) */
 #undef USE_PAM
 
@@ -914,9 +908,6 @@
 /* Define to select unnamed POSIX semaphores. */
 #undef USE_UNNAMED_POSIX_SEMAPHORES
 
-/* Define to use native Windows API for random number generation */
-#undef USE_WIN32_RANDOM
-
 /* Define to select Win32-style semaphores. */
 #undef USE_WIN32_SEMAPHORES
 
diff --git a/src/port/pg_strong_random.c b/src/port/pg_strong_random.c
index 6d85f50b7c8..12bbd7fb08b 100644
--- a/src/port/pg_strong_random.c
+++ b/src/port/pg_strong_random.c
@@ -24,107 +24,15 @@
 #include <unistd.h>
 #include <sys/time.h>
 
-#ifdef USE_OPENSSL_RANDOM
-#include <openssl/rand.h>
-#endif
-#ifdef USE_WIN32_RANDOM
-#include <wincrypt.h>
-#endif
-
-#ifdef USE_WIN32_RANDOM
-/*
- * Cache a global crypto provider that only gets freed when the process
- * exits, in case we need random numbers more than once.
- */
-static HCRYPTPROV hProvider = 0;
-#endif
-
-#if defined(USE_DEV_URANDOM)
-/*
- * Read (random) bytes from a file.
- */
-static bool
-random_from_file(const char *filename, void *buf, size_t len)
-{
-	int			f;
-	char	   *p = buf;
-	ssize_t		res;
-
-	f = open(filename, O_RDONLY, 0);
-	if (f == -1)
-		return false;
-
-	while (len)
-	{
-		res = read(f, p, len);
-		if (res <= 0)
-		{
-			if (errno == EINTR)
-				continue;		/* interrupted by signal, just retry */
-
-			close(f);
-			return false;
-		}
-
-		p += res;
-		len -= res;
-	}
-
-	close(f);
-	return true;
-}
-#endif
-
 /*
- * pg_strong_random_init
- *
- * Initialize the randomness state of "strong" random numbers.  This is invoked
- * *after* forking a process, and should include initialization steps specific
- * to the chosen random source to prove fork-safety.
- */
-void
-pg_strong_random_init(void)
-{
-#if defined(USE_OPENSSL)
-	/*
-	 * Make sure processes do not share OpenSSL randomness state. We need to
-	 * call this even if pg_strong_random is implemented using another source
-	 * for random numbers to ensure fork-safety in our TLS backend.  This is no
-	 * longer required in OpenSSL 1.1.1 and later versions, but until we drop
-	 * support for version < 1.1.1 we need to do this.
-	*/
-	RAND_poll();
-#endif
-
-#if defined(USE_OPENSSL_RANDOM)
-	/*
-	 * In case the backend is using the PRNG from OpenSSL without being built
-	 * with support for OpenSSL, make sure to perform post-fork initialization.
-	 * If the backend is using OpenSSL then we have already performed this
-	 * step. The same version caveat as discussed in the comment above applies
-	 * here as well.
-	 */
-#ifndef USE_OPENSSL
-	RAND_poll();
-#endif
-
-#elif defined(USE_WIN32_RANDOM)
-	/* no initialization needed for WIN32 */
-
-#elif defined(USE_DEV_URANDOM)
-	/* no initialization needed for /dev/urandom */
-
-#else
-#error no source of random numbers configured
-#endif
-}
-
-/*
- * pg_strong_random
+ * pg_strong_random & pg_strong_random_init
  *
  * Generate requested number of random bytes. The returned bytes are
  * cryptographically secure, suitable for use e.g. in authentication.
  *
+ * Before pg_strong_random is called in any process, the generator must first
+ * be initialized by calling pg_strong_random_init().
+ *
  * We rely on system facilities for actually generating the numbers.
  * We support a number of sources:
  *
@@ -132,21 +40,32 @@ pg_strong_random_init(void)
  * 2. Windows' CryptGenRandom() function
  * 3. /dev/urandom
  *
- * The configure script will choose which one to use, and set
- * a USE_*_RANDOM flag accordingly.
- *
  * Returns true on success, and false if none of the sources
  * were available. NB: It is important to check the return value!
  * Proceeding with key generation when no random data was available
  * would lead to predictable keys and security issues.
  */
-bool
-pg_strong_random(void *buf, size_t len)
+
+
+
+#ifdef USE_OPENSSL
+
+#include <openssl/rand.h>
+
+void
+pg_strong_random_init(void)
 {
 	/*
-	 * When built with OpenSSL, use OpenSSL's RAND_bytes function.
+	 * Make sure processes do not share OpenSSL randomness state.  This is no
+	 * longer required in OpenSSL 1.1.1 and later versions, but until we drop
+	 * support for version < 1.1.1 we need to do this.
 	 */
-#if defined(USE_OPENSSL_RANDOM)
+	RAND_poll();
+}
+
+bool
+pg_strong_random(void *buf, size_t len)
+{
 	int			i;
 
 	/*
@@ -174,11 +93,26 @@ pg_strong_random(void *buf, size_t len)
 	if (RAND_bytes(buf, len) == 1)
 		return true;
 	return false;
+}
 
-	/*
-	 * Windows has CryptoAPI for strong cryptographic numbers.
-	 */
-#elif defined(USE_WIN32_RANDOM)
+#elif WIN32
+
+#include <wincrypt.h>
+/*
+ * Cache a global crypto provider that only gets freed when the process
+ * exits, in case we need random numbers more than once.
+ */
+static HCRYPTPROV hProvider = 0;
+
+void
+pg_strong_random_init(void)
+{
+	/* No initialization needed on WIN32 */
+}
+
+bool
+pg_strong_random(void *buf, size_t len)
+{
 	if (hProvider == 0)
 	{
 		if (!CryptAcquireContext(&hProvider,
@@ -201,17 +135,48 @@ pg_strong_random(void *buf, size_t len)
 			return true;
 	}
 	return false;
+}
 
-	/*
-	 * Read /dev/urandom ourselves.
-	 */
-#elif defined(USE_DEV_URANDOM)
-	if (random_from_file("/dev/urandom", buf, len))
-		return true;
-	return false;
+#else							/* not USE_OPENSSL or WIN32 */
 
-#else
-	/* The autoconf script should not have allowed this */
-#error no source of random numbers configured
-#endif
+/*
+ * Without OpenSSL or Win32 support, just read /dev/urandom ourselves.
+ */
+
+void
+pg_strong_random_init(void)
+{
+	/* No initialization needed */
+}
+
+bool
+pg_strong_random(void *buf, size_t len)
+{
+	int			f;
+	char	   *p = buf;
+	ssize_t		res;
+
+	f = open("/dev/urandom", O_RDONLY, 0);
+	if (f == -1)
+		return false;
+
+	while (len)
+	{
+		res = read(f, p, len);
+		if (res <= 0)
+		{
+			if (errno == EINTR)
+				continue;		/* interrupted by signal, just retry */
+
+			close(f);
+			return false;
+		}
+
+		p += res;
+		len -= res;
+	}
+
+	close(f);
+	return true;
 }
+#endif
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index 17e480546cf..22d6abd3674 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -475,7 +475,6 @@ sub GenerateFiles
 		USE_ASSERT_CHECKING => $self->{options}->{asserts} ? 1 : undef,
 		USE_BONJOUR         => undef,
 		USE_BSD_AUTH        => undef,
-		USE_DEV_URANDOM     => undef,
 		USE_ICU => $self->{options}->{icu} ? 1 : undef,
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
@@ -483,7 +482,6 @@ sub GenerateFiles
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
 		USE_OPENSSL                => undef,
-		USE_OPENSSL_RANDOM         => undef,
 		USE_PAM                    => undef,
 		USE_SLICING_BY_8_CRC32C    => undef,
 		USE_SSE42_CRC32C           => undef,
@@ -492,7 +490,6 @@ sub GenerateFiles
 		USE_SYSV_SEMAPHORES                 => undef,
 		USE_SYSV_SHARED_MEMORY              => undef,
 		USE_UNNAMED_POSIX_SEMAPHORES        => undef,
-		USE_WIN32_RANDOM                    => 1,
 		USE_WIN32_SEMAPHORES                => 1,
 		USE_WIN32_SHARED_MEMORY             => 1,
 		WCSTOMBS_L_IN_XLOCALE               => undef,