[Qemu-devel] [PATCH v2 05/14] crypto: Use getrandom for qcrypto_random_bytes

[Richard Henderson]

Prefer it to direct use of /dev/urandom.

Cc: Daniel P. Berrangé <berra...@redhat.com>
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
 crypto/random-platform.c | 21 +++++++++++++++++++++
 configure                | 18 +++++++++++++++++-
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/crypto/random-platform.c b/crypto/random-platform.c
index 8bfce99a65..bdaa8fbbfb 100644
--- a/crypto/random-platform.c
+++ b/crypto/random-platform.c
@@ -26,6 +26,8 @@
 #ifdef _WIN32
 #include <wincrypt.h>
 static HCRYPTPROV hCryptProv;
+#elif defined(CONFIG_GETRANDOM)
+#include <sys/random.h>
 #else
 static int fd; /* a file handle to either /dev/urandom or /dev/random */
 #endif
@@ -39,6 +41,12 @@ int qcrypto_random_init(Error **errp)
                          "Unable to create cryptographic provider");
         return -1;
     }
+#elif defined(CONFIG_GETRANDOM)
+    errno = 0;
+    if (getrandom(NULL, 0, 0) < 0 && errno == ENOSYS) {
+        error_setg_errno(errp, errno, "getrandom");
+        return -1;
+    }
 #else
     /* TBD perhaps also add support for BSD getentropy / Linux
      * getrandom syscalls directly */
@@ -65,6 +73,19 @@ int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
                          "Unable to read random bytes");
         return -1;
     }
+#elif defined(CONFIG_GETRANDOM)
+    while (buflen > 0) {
+        ssize_t got = getrandom(buf, buflen, 0);
+        if (unlikely(got < 0)) {
+            if (errno != EINTR) {
+                error_setg_errno(errp, errno, "getrandom");
+                return -1;
+            }
+        } else {
+            buflen -= got;
+            buf += got;
+        }
+    }
 #else
     while (buflen > 0) {
         ssize_t got = read(fd, buf, buflen);
diff --git a/configure b/configure
index 8992b3aade..6a32284d26 100755
--- a/configure
+++ b/configure
@@ -5783,6 +5783,20 @@ if compile_prog "" "" ; then
     have_utmpx=yes
 fi
 
+##########################################
+# check for getrandom()
+
+have_getrandom=no
+cat > $TMPC << EOF
+#include <sys/random.h>
+int main(void) {
+    return getrandom(0, 0, GRND_NONBLOCK);
+}
+EOF
+if compile_prog "" "" ; then
+    have_getrandom=yes
+fi
+
 ##########################################
 # checks for sanitizers
 
@@ -7170,7 +7184,9 @@ fi
 if test "$have_utmpx" = "yes" ; then
   echo "HAVE_UTMPX=y" >> $config_host_mak
 fi
-
+if test "$have_getrandom" = "yes" ; then
+  echo "CONFIG_GETRANDOM=y" >> $config_host_mak
+fi
 if test "$ivshmem" = "yes" ; then
   echo "CONFIG_IVSHMEM=y" >> $config_host_mak
 fi
-- 
2.17.1