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.

1 files changed, 76 insertions, 0 deletions

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;
+}