random-util: add crypto_random_bytes_allocate_iovec()

Just a simple helper that allocates some memory, initializes it
randomly, and places this in a struct iovec.

src/basic/random-util.c

@@ -21,6 +21,7 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "io-util.h"
+#include "iovec-util.h"
 #include "missing_random.h"
 #include "missing_syscall.h"
 #include "missing_threads.h"
@@ -164,6 +165,24 @@ int crypto_random_bytes(void *p, size_t n) {
         return loop_read_exact(fd, p, n, false);
 }
 
+int crypto_random_bytes_allocate_iovec(size_t n, struct iovec *ret) {
+        _cleanup_free_ void *p = NULL;
+        int r;
+
+        assert(ret);
+
+        p = malloc(MAX(n, 1U));
+        if (!p)
+                return -ENOMEM;
+
+        r = crypto_random_bytes(p, n);
+        if (r < 0)
+                return r;
+
+        *ret = IOVEC_MAKE(TAKE_PTR(p), n);
+        return 0;
+}
+
 size_t random_pool_size(void) {
         _cleanup_free_ char *s = NULL;
         int r;

src/basic/random-util.h

@@ -4,9 +4,11 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <sys/uio.h>
 
 void random_bytes(void *p, size_t n); /* Returns random bytes suitable for most uses, but may be insecure sometimes. */
 int crypto_random_bytes(void *p, size_t n); /* Returns secure random bytes after waiting for the RNG to initialize. */
+int crypto_random_bytes_allocate_iovec(size_t n, struct iovec *ret);
 
 static inline uint64_t random_u64(void) {
         uint64_t u;