add load-random-seed

1 files changed, 65 insertions, 0 deletions

diff --git a/load-random-seed.c b/load-random-seed.c
new file mode 100644
index 0000000..491afba
--- /dev/null
+++ b/load-random-seed.c
@@ -0,0 +1,65 @@
+#include <fcntl.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+// musl forbids include/linux
+#define RNDADDENTROPY   _IOW( 'R', 0x03, int [2] )
+
+#define RAND_POOL_SIZE 512
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        fputs("usage: load-random-seed FILE\n", stderr);
+        exit(1);
+    }
+
+    int seed_fd = open(argv[1], O_RDONLY);
+    if (seed_fd == -1) {
+        perror("error opening seed file");
+        exit(1);
+    }
+    struct {
+        int entropy_count;
+        int buf_size;
+        char buf[RAND_POOL_SIZE];
+    } rpi = {
+        .entropy_count = RAND_POOL_SIZE * CHAR_BIT,
+        .buf_size = RAND_POOL_SIZE
+    };
+    size_t sz = 0;
+    do {
+        ssize_t r = read(seed_fd, &rpi.buf[sz], RAND_POOL_SIZE - sz);
+        if (r == -1) {
+            perror("error reading seed file");
+            exit(1);
+        }
+        sz += r;
+    } while (sz < RAND_POOL_SIZE);
+
+    if (close(seed_fd) == -1) {
+        perror("error closing seed file");
+        exit(1);
+    }
+
+    int urandom_fd = open("/dev/urandom", O_RDWR);
+    if (urandom_fd == -1) {
+        perror("error opening /dev/urandom");
+        exit(1);
+    }
+    if (ioctl(urandom_fd, RNDADDENTROPY, &rpi) == -1) {
+        perror("error adding entropy");
+        exit(1);
+    }
+    if (close(urandom_fd) == -1) {
+        perror("error closing /dev/urandom");
+        exit(1);
+    }
+
+    return 0;
+}