crypto lib

src/crypto/random.c

@@ -0,0 +1,62 @@
+#include <assert.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "hash.h"
+#include "random.h"
+
+static void generate_system_random_bytes(size_t n, void *result) {
+  int fd;
+  if ((fd = open("/dev/urandom", O_RDONLY | O_NOCTTY | O_CLOEXEC)) < 0) {
+    err(EXIT_FAILURE, "open /dev/urandom");
+  }
+  for (;;) {
+    ssize_t res = read(fd, result, n);
+    if ((size_t) res == n) {
+      break;
+    }
+    if (res < 0) {
+      if (errno != EINTR) {
+        err(EXIT_FAILURE, "read /dev/urandom");
+      }
+    } else if (res == 0) {
+      errx(EXIT_FAILURE, "read /dev/urandom: end of file");
+    } else {
+      result = padd(result, (size_t) res);
+      n -= (size_t) res;
+    }
+  }
+  if (close(fd) < 0) {
+    err(EXIT_FAILURE, "close /dev/urandom");
+  }
+}
+
+static struct keccak_state state;
+
+void init_random(void) {
+  generate_system_random_bytes(32, &state);
+}
+
+void generate_random_bytes(size_t n, void *result) {
+  if (n == 0) {
+    return;
+  }
+  for (;;) {
+    keccak_permutation(&state);
+    if (n <= HASH_DATA_AREA) {
+      memcpy(result, &state, n);
+      return;
+    } else {
+      memcpy(result, &state, HASH_DATA_AREA);
+      result = padd(result, HASH_DATA_AREA);
+      n -= HASH_DATA_AREA;
+    }
+  }
+}