mcookie: use lib/randutils

The mcookie should reuse existing code, and there is definitely no need
to prefer /dev/random for this utility.  See reference for explanation
about later statement.

References: http://www.2uo.de/myths-about-urandom/
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

diff --git a/include/randutils.h b/include/randutils.h
index dec5e355a43947a0133087a9ef2fcd1181b0da99..17e2a02fac07701f2f01c94216a3ddc91c3766ba 100644 (file)
--- a/include/randutils.h
+++ b/include/randutils.h
@@ -8,5 +8,6 @@
 
 extern int random_get_fd(void);
 extern void random_get_bytes(void *buf, size_t nbytes);
+extern const char *random_tell_source(void);
 
 #endif

diff --git a/lib/randutils.c b/lib/randutils.c
index ed79aad920fe49950400b99ca37e7184cd3c04f9..684ac0ac160af22e0442368f21c6881884a9ae0d 100644 (file)
--- a/lib/randutils.c
+++ b/lib/randutils.c
@@ -15,7 +15,9 @@
 
 #include <sys/syscall.h>
 
+#include "c.h"
 #include "randutils.h"
+#include "nls.h"
 
 #ifdef HAVE_TLS
 #define THREAD_LOCAL static __thread
@@ -108,6 +110,26 @@ void random_get_bytes(void *buf, size_t nbytes)
        return;
 }
 
+
+/*
+ * Tell source of randomness.
+ */
+const char *random_tell_source(void)
+{
+       size_t i;
+       static const char *random_sources[] = {
+               "/dev/urandom",
+               "/dev/random"
+       };
+
+       for (i = 0; i < ARRAY_SIZE(random_sources); i++) {
+               if (!access(random_sources[i], R_OK))
+                       return random_sources[i];
+       }
+
+       return _("libc pseudo-random functions");
+}
+
 #ifdef TEST_PROGRAM
 int main(int argc __attribute__ ((__unused__)),
          char *argv[] __attribute__ ((__unused__)))

diff --git a/misc-utils/Makemodule.am b/misc-utils/Makemodule.am
index 05407de9b3211456ddec4d204ad9460a4eae484d..f31e4e18553d0daa0887c9faf86e43b238029917 100644 (file)
--- a/misc-utils/Makemodule.am
+++ b/misc-utils/Makemodule.am
@@ -32,6 +32,7 @@ look_SOURCES = misc-utils/look.c
 usrbin_exec_PROGRAMS += mcookie
 dist_man_MANS += misc-utils/mcookie.1
 mcookie_SOURCES = misc-utils/mcookie.c lib/md5.c
+mcookie_LDADD = $(LDADD) libcommon.la
 
 usrbin_exec_PROGRAMS += namei
 dist_man_MANS += misc-utils/namei.1

diff --git a/misc-utils/mcookie.1 b/misc-utils/mcookie.1
index fc7e030478d9516f07a1edd33e59b5e55b3b5911..b974ff0f929464c4648235890d9d5742eed78351 100644 (file)
--- a/misc-utils/mcookie.1
+++ b/misc-utils/mcookie.1
@@ -1,6 +1,6 @@
 .\" mcookie.1 --
 .\" Public Domain 1995 Rickard E. Faith (faith@cs.unc.edu)
-.TH MCOOKIE 1 "June 2011" "util-linux" "User Commands"
+.TH MCOOKIE 1 "March 2014" "util-linux" "User Commands"
 .SH NAME
 mcookie \- generate magic cookies for xauth
 .SH SYNOPSIS
@@ -15,23 +15,21 @@ xauth add :0 . `mcookie`
 .RE
 .PP
 The "random" number generated is actually the output of the MD5 message
-digest fed with various pieces of random information: the current time, the
-process id, the parent process id, and optionally the contents of an input
-file. and several bytes of information from the first of the following
-devices which is present:
-.IR /dev/random ,
+digest fed with random information from one of the sources
 .IR /dev/urandom ,
-files in
-.IR /proc ,
-.IR /dev/audio .
+.IR /dev/random ,
+or
+.I "libc pseudo-random functions"
+in this preference order.
 .SH OPTIONS
 .TP
 \fB\-f\fR, \fB\-\-file\fR=\fIFILE\fR
-Use file as a macig cookie seed. When file is defined as `-' character
-input is read from stdin.
+Use additional file as a macig cookie random seed.  When file is defined
+as '-' character input is read from stdin.
 .TP
 \fB\-v\fR, \fB\-\-verbose\fR
-Explain what is being done.
+Inform where randomness originated, with amount of entropy read from each
+source.
 .TP
 \fB\-V\fR, \fB\-\-version\fR
 Display version information and exit.
@@ -39,27 +37,18 @@ Display version information and exit.
 \fB\-h\fR, \fB\-\-help\fR
 Display help text and exit.
 .SH BUGS
-The entropy in the generated 128-bit is probably quite small (and,
-therefore, vulnerable to attack) unless a non-pseudorandom number generator
-is used (e.g.,
-.I /dev/random
-under Linux).
-.PP
-It is assumed that none of the devices opened will block.
+It is assumed that none of the randomness sources will block.
 .SH FILES
-.I /dev/random
-.br
 .I /dev/urandom
 .br
-.I /dev/audio
-.br
-.I /proc/stat
-.br
-.I /proc/loadavg
+.I /dev/random
 .SH "SEE ALSO"
 .BR X (1),
 .BR xauth (1),
-.BR md5sum (1)
+.BR md5sum (1),
+.BR rand (3)
 .SH AVAILABILITY
 The mcookie command is part of the util-linux package and is available from
-ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
+.UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
+Linux Kernel Archive
+.UE .

diff --git a/misc-utils/mcookie.c b/misc-utils/mcookie.c
index 3761c4b8cae7ab253d25a9ccc760f083b3bdcf44..33e10eb4a7a7952e10bae70223183017df7fe6e2 100644 (file)
--- a/misc-utils/mcookie.c
+++ b/misc-utils/mcookie.c
@@ -22,6 +22,7 @@
 #include "md5.h"
 #include "nls.h"
 #include "closestream.h"
+#include "randutils.h"
 
 #include <fcntl.h>
 #include <getopt.h>
@@ -31,21 +32,11 @@
 #include <sys/time.h>
 #include <unistd.h>
 
-#define BUFFERSIZE     4096
-
-struct rngs {
-       const char *path;
-       int minlength, maxlength;
-} rngs[] = {
-       {"/dev/random",         16, 16},  /* 16 bytes = 128 bits suffice */
-       {"/proc/interrupts",     0,  0},
-       {"/proc/slabinfo",       0,  0},
-       {"/proc/stat",           0,  0},
-       {"/dev/urandom",        32, 64},
+enum {
+       BUFFERSIZE = 4096,
+       RAND_BYTES = 128
 };
 
-#define RNGS (sizeof(rngs)/sizeof(struct rngs))
-
 /* The basic function to hash a file */
 static off_t hash_file(struct MD5Context *ctx, int fd)
 {
@@ -83,15 +74,11 @@ int main(int argc, char **argv)
        size_t i;
        struct MD5Context ctx;
        unsigned char digest[MD5LENGTH];
-       unsigned char buf[BUFFERSIZE];
+       unsigned char buf[RAND_BYTES];
        int fd;
        int c;
-       pid_t pid;
        char *file = NULL;
        int verbose = 0;
-       int r;
-       struct timeval tv;
-       struct timezone tz;
 
        static const struct option longopts[] = {
                {"file", required_argument, NULL, 'f'},
@@ -125,13 +112,6 @@ int main(int argc, char **argv)
                }
 
        MD5Init(&ctx);
-       gettimeofday(&tv, &tz);
-       MD5Update(&ctx, (unsigned char *) &tv, sizeof(tv));
-
-       pid = getppid();
-       MD5Update(&ctx, (unsigned char *) &pid, sizeof(pid));
-       pid = getpid();
-       MD5Update(&ctx, (unsigned char *) &pid, sizeof(pid));
 
        if (file) {
                int count = 0;
@@ -158,28 +138,11 @@ int main(int argc, char **argv)
                }
        }
 
-       for (i = 0; i < RNGS; i++) {
-               if ((fd = open(rngs[i].path, O_RDONLY | O_NONBLOCK)) >= 0) {
-                       int count = sizeof(buf);
-
-                       if (rngs[i].maxlength && count > rngs[i].maxlength)
-                               count = rngs[i].maxlength;
-                       r = read(fd, buf, count);
-                       if (r > 0)
-                               MD5Update(&ctx, buf, r);
-                       else
-                               r = 0;
-                       close(fd);
-                       if (verbose)
-                               fprintf(stderr,
-                                       P_("Got %d byte from %s\n",
-                                          "Got %d bytes from %s\n", r),
-                                       r, rngs[i].path);
-                       if (rngs[i].minlength && r >= rngs[i].minlength)
-                               break;
-               } else if (verbose)
-                       warn(_("cannot open %s"), rngs[i].path);
-       }
+       random_get_bytes(&buf, RAND_BYTES);
+       MD5Update(&ctx, buf, RAND_BYTES);
+       if (verbose)
+               fprintf(stderr,
+                       _("Got %d bytes from %s\n"), RAND_BYTES, random_tell_source());
 
        MD5Final(digest, &ctx);
        for (i = 0; i < MD5LENGTH; i++)