[git] GCRYPT - branch, master, updated. libgcrypt-1.7.0-3-gee5a322

[by Werner Koch]

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       via  ee5a32226a7ca4ab067864e06623fc11a1768900 (commit)
      from  4545372c0f8dd35aef2a7abc12b588ed1a4a0363 (commit)

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- Log -----------------------------------------------------------------
commit ee5a32226a7ca4ab067864e06623fc11a1768900
Author: Werner Koch <wk at gnupg.org>
Date:   Tue Apr 26 15:46:30 2016 +0200

    random: Try to use getrandom() instead of /dev/urandom (Linux only).
    
    * configure.ac: Check for syscall.
    * random/rndlinux.c [HAVE_SYSCALL]: Include sys/syscall.h.
    (_gcry_rndlinux_gather_random): Use getrandom is available.
    
    Signed-off-by: Werner Koch <wk at gnupg.org>

diff --git a/configure.ac b/configure.ac
index 5f9f711..ad06dfd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1514,7 +1514,7 @@ AC_CHECK_FUNCS(strtoul memmove stricmp atexit raise)
 # Other checks
 AC_CHECK_FUNCS(strerror rand mmap getpagesize sysconf waitpid wait4)
 AC_CHECK_FUNCS(gettimeofday getrusage gethrtime clock_gettime syslog)
-AC_CHECK_FUNCS(fcntl ftruncate flockfile)
+AC_CHECK_FUNCS(syscall fcntl ftruncate flockfile)
 
 GNUPG_CHECK_MLOCK
 
diff --git a/random/rndlinux.c b/random/rndlinux.c
index 0cb65df..592b9ac 100644
--- a/random/rndlinux.c
+++ b/random/rndlinux.c
@@ -32,6 +32,10 @@
 #include <string.h>
 #include <unistd.h>
 #include <fcntl.h>
+#if defined(__linux__) && defined(HAVE_SYSCALL)
+# include <sys/syscall.h>
+#endif
+
 #include "types.h"
 #include "g10lib.h"
 #include "rand-internal.h"
@@ -232,6 +236,50 @@ _gcry_rndlinux_gather_random (void (*add)(const void*, size_t,
             }
         }
 
+      /* If we have a modern Linux kernel and we want to read from the
+       * the non-blocking /dev/urandom, we first try to use the new
+       * getrandom syscall.  That call guarantees that the kernel's
+       * RNG has been properly seeded before returning any data.  This
+       * is different from /dev/urandom which may, due to its
+       * non-blocking semantics, return data even if the kernel has
+       * not been properly seeded.  Unfortunately we need to use a
+       * syscall and not a new device and thus we are not able to use
+       * select(2) to have a timeout. */
+#if defined(__linux__) && defined(HAVE_SYSCALL) && defined(__NR_getrandom)
+      if (fd == fd_urandom)
+        {
+          long ret;
+          size_t nbytes;
+
+          do
+            {
+              nbytes = length < sizeof(buffer)? length : sizeof(buffer);
+              if (nbytes > 256)
+                nbytes = 256;
+              ret = syscall (__NR_getrandom,
+                             (void*)buffer, (size_t)nbytes, (unsigned int)0);
+            }
+          while (ret == -1 && errno == EINTR);
+          if (ret == -1 && errno == ENOSYS)
+            ; /* The syscall is not supported - fallback to /dev/urandom.  */
+          else
+            { /* The syscall is supported.  Some sanity checks.  */
+              if (ret == -1)
+                log_fatal ("unexpected error from getrandom: %s\n",
+                           strerror (errno));
+              else if (ret != nbytes)
+                log_fatal ("getrandom returned only"
+                           " %ld of %zu requested bytes\n", ret, nbytes);
+
+              log_debug ("getrandom returned %zu requested bytes\n", nbytes);
+              (*add)(buffer, nbytes, origin);
+              length -= nbytes;
+              continue; /* until LENGTH is zero.  */
+            }
+          log_debug ("syscall(getrandom) not supported; errno = %d\n", errno);
+        }
+#endif
+
       do
         {
           size_t nbytes;

-----------------------------------------------------------------------

Summary of changes:
 configure.ac      |  2 +-
 random/rndlinux.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)


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