[Libguestfs] [PATCH 39/67] lib: Turn 'random_chars' function used by libvirt backend into utility function.

[Richard W.M. Jones]

From: "Richard W.M. Jones" <rjones at redhat.com>

(cherry picked from commit e5285cc4210683887a5a4a853fe4e6a72c23e74d)
---
 src/guestfs-internal-frontend.h |  1 +
 src/launch-libvirt.c            | 34 ++--------------------------------
 src/utils.c                     | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/src/guestfs-internal-frontend.h b/src/guestfs-internal-frontend.h
index db6122f..2070fa8 100644
--- a/src/guestfs-internal-frontend.h
+++ b/src/guestfs-internal-frontend.h
@@ -97,6 +97,7 @@ extern size_t guestfs___count_strings (char *const *);
 extern char *guestfs___concat_strings (char *const *);
 extern char *guestfs___join_strings (const char *sep, char *const *);
 extern char *guestfs___exit_status_to_string (int status, const char *cmd_name, char *buffer, size_t buflen);
+extern int guestfs___random_string (char *ret, size_t len);
 
 /* These functions are used internally by the CLEANUP_* macros.
  * Don't call them directly.
diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
index 826d40d..de725e0 100644
--- a/src/launch-libvirt.c
+++ b/src/launch-libvirt.c
@@ -131,7 +131,6 @@ static void debug_socket_permissions (guestfs_h *g);
 static void libvirt_error (guestfs_h *g, const char *fs, ...) __attribute__((format (printf,2,3)));
 static int is_custom_qemu (guestfs_h *g);
 static int is_blk (const char *path);
-static int random_chars (char *ret, size_t len);
 static void ignore_errors (void *ignore, virErrorPtr ignore2);
 static char *make_qcow2_overlay (guestfs_h *g, const char *backing_device, const char *format, const char *selinux_imagelabel);
 static int make_drive_priv (guestfs_h *g, struct drive *drv, const char *selinux_imagelabel);
@@ -791,8 +790,8 @@ construct_libvirt_xml_name (guestfs_h *g,
 {
   char name[DOMAIN_NAME_LEN+1];
 
-  if (random_chars (name, DOMAIN_NAME_LEN) == -1) {
-    perrorf (g, "/dev/urandom");
+  if (guestfs___random_string (name, DOMAIN_NAME_LEN) == -1) {
+    perrorf (g, "guestfs___random_string");
     return -1;
   }
 
@@ -1487,35 +1486,6 @@ is_blk (const char *path)
   return S_ISBLK (statbuf.st_mode);
 }
 
-static int
-random_chars (char *ret, size_t len)
-{
-  int fd;
-  size_t i;
-  unsigned char c;
-  int saved_errno;
-
-  fd = open ("/dev/urandom", O_RDONLY|O_CLOEXEC);
-  if (fd == -1)
-    return -1;
-
-  for (i = 0; i < len; ++i) {
-    if (read (fd, &c, 1) != 1) {
-      saved_errno = errno;
-      close (fd);
-      errno = saved_errno;
-      return -1;
-    }
-    ret[i] = "0123456789abcdefghijklmnopqrstuvwxyz"[c % 36];
-  }
-  ret[len] = '\0';
-
-  if (close (fd) == -1)
-    return -1;
-
-  return 0;
-}
-
 static void
 ignore_errors (void *ignore, virErrorPtr ignore2)
 {
diff --git a/src/utils.c b/src/utils.c
index 358c124..4a9ae96 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -22,6 +22,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <libintl.h>
@@ -125,3 +127,40 @@ guestfs___exit_status_to_string (int status, const char *cmd_name,
 
   return buffer;
 }
+
+/* Notes:
+ *
+ * The 'ret' buffer must have length len+1 in order to store the final
+ * \0 character.
+ *
+ * There is about 5 bits of randomness per output character (so about
+ * 5*len bits of randomness in the resulting string).
+ */
+int
+guestfs___random_string (char *ret, size_t len)
+{
+  int fd;
+  size_t i;
+  unsigned char c;
+  int saved_errno;
+
+  fd = open ("/dev/urandom", O_RDONLY|O_CLOEXEC);
+  if (fd == -1)
+    return -1;
+
+  for (i = 0; i < len; ++i) {
+    if (read (fd, &c, 1) != 1) {
+      saved_errno = errno;
+      close (fd);
+      errno = saved_errno;
+      return -1;
+    }
+    ret[i] = "0123456789abcdefghijklmnopqrstuvwxyz"[c % 36];
+  }
+  ret[len] = '\0';
+
+  if (close (fd) == -1)
+    return -1;
+
+  return 0;
+}
-- 
1.8.3.1