From 6cff8357023adb4d5c9daa027522f883f3905f4c Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Thu, 22 Mar 2018 14:58:29 +0000
Subject: win32: allow use of shell's PRNG for /dev/urandom

Allow either ISAAC or the shell's built-in pseudo-random number
generator to be used for /dev/urandom.  The latter is smaller so
it's the default.
---
 win32/Kbuild      | 11 ++++----
 win32/sh_random.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+), 5 deletions(-)
 create mode 100644 win32/sh_random.c

(limited to 'win32')

diff --git a/win32/Kbuild b/win32/Kbuild
index 00950e0f7..f8c8fb5af 100644
--- a/win32/Kbuild
+++ b/win32/Kbuild
@@ -7,18 +7,19 @@ lib-y:=
 lib-$(CONFIG_PLATFORM_MINGW32) += env.o
 lib-$(CONFIG_PLATFORM_MINGW32) += fnmatch.o
 lib-$(CONFIG_PLATFORM_MINGW32) += fsync.o
+lib-$(CONFIG_PLATFORM_MINGW32) += inet_pton.o
 lib-$(CONFIG_PLATFORM_MINGW32) += ioctl.o
-lib-$(CONFIG_PLATFORM_MINGW32) += isaac.o
+lib-$(CONFIG_FEATURE_PRNG_ISAAC) += isaac.o
 lib-$(CONFIG_PLATFORM_MINGW32) += mingw.o
 lib-$(CONFIG_PLATFORM_MINGW32) += process.o
-lib-$(CONFIG_PLATFORM_MINGW32) += regex.o
+lib-$(CONFIG_PLATFORM_MINGW32) += mntent.o
 lib-$(CONFIG_PLATFORM_MINGW32) += net.o
-lib-$(CONFIG_PLATFORM_MINGW32) += inet_pton.o
 lib-$(CONFIG_PLATFORM_MINGW32) += poll.o
-lib-$(CONFIG_PLATFORM_MINGW32) += select.o
 lib-$(CONFIG_PLATFORM_MINGW32) += popen.o
+lib-$(CONFIG_PLATFORM_MINGW32) += regex.o
+lib-$(CONFIG_PLATFORM_MINGW32) += select.o
+lib-$(CONFIG_FEATURE_PRNG_SHELL) += sh_random.o
 lib-$(CONFIG_PLATFORM_MINGW32) += statfs.o
-lib-$(CONFIG_PLATFORM_MINGW32) += mntent.o
 lib-$(CONFIG_PLATFORM_MINGW32) += strptime.o
 lib-$(CONFIG_PLATFORM_MINGW32) += system.o
 lib-$(CONFIG_PLATFORM_MINGW32) += termios.o
diff --git a/win32/sh_random.c b/win32/sh_random.c
new file mode 100644
index 000000000..2948e4a55
--- /dev/null
+++ b/win32/sh_random.c
@@ -0,0 +1,76 @@
+#include "libbb.h"
+#include "../shell/random.h"
+
+/* call 'fn' to put data in 'dt' then copy it to generator state */
+#define GET_DATA(fn, dt) \
+	fn(&dt); \
+	u = (uint32_t *)&dt; \
+	for (j=0; j<sizeof(dt)/sizeof(uint32_t); ++j) { \
+		state[i++%2] ^= *u++; \
+	}
+
+/*
+ * Obtain a few bytes of random-ish data to initialise the generator.
+ * This is unlikely to be very robust:  don't rely on it for
+ * anything that needs to be secure.
+ */
+static void get_entropy(uint32_t state[2])
+{
+	int i, j;
+	SYSTEMTIME tm;
+	MEMORYSTATUS ms;
+	SYSTEM_INFO si;
+	LARGE_INTEGER pc;
+	uint32_t *u;
+
+	i = 0;
+	state[i++%2] ^= (uint32_t)GetCurrentProcessId();
+	state[i++%2] ^= (uint32_t)GetCurrentThreadId();
+	state[i++%2] ^= (uint32_t)GetTickCount();
+
+	GET_DATA(GetLocalTime, tm)
+	GET_DATA(GlobalMemoryStatus, ms)
+	GET_DATA(GetSystemInfo, si)
+	GET_DATA(QueryPerformanceCounter, pc)
+
+#if 0
+	{
+		unsigned char *p = (unsigned char *)state;
+
+		for (j=0; j<8; ++j) {
+			fprintf(stderr, "%02x", *p++);
+			if ((j&3) == 3) {
+				fprintf(stderr, " ");
+			}
+		}
+		fprintf(stderr, "\n");
+	}
+#endif
+}
+
+ssize_t get_random_bytes(void *buf, ssize_t count)
+{
+	static random_t rnd;
+	ssize_t save_count = count;
+	uint32_t value;
+	unsigned char *ptr = (unsigned char *)&value;
+
+	if (buf == NULL || count < 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (UNINITED_RANDOM_T(&rnd)) {
+		uint32_t state[2] = {0, 0};
+
+		get_entropy(state);
+		INIT_RANDOM_T(&rnd, state[0] ? state[0] : 1, state[1]);
+	}
+
+	for (;count > 0; buf+=4, count-=4) {
+		value = full_random(&rnd);
+		memcpy(buf, ptr, count >= 4 ? 4 : count);
+	}
+
+	return save_count;
+}
-- 
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