[PATCH 5/5] mcookie: add --max-size option

Sami Kerola
2014-03-08T21:43:39Z

Just in case someone wants to add entropy from device with invocation
demonstrated below.

$ mcookie --file /dev/urandom --max-size 64k

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
---
misc-utils/mcookie.1 | 15 +++++++++++++++
misc-utils/mcookie.c | 29 ++++++++++++++++++++++++-----
2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/misc-utils/mcookie.1 b/misc-utils/mcookie.1
index df6137f..1b6ac76 100644
--- a/misc-utils/mcookie.1
+++ b/misc-utils/mcookie.1
@@ -27,6 +27,21 @@ in this preference order.
Use additional file as a macig cookie random seed. When file is defined
as '-' character input is read from stdin.
.TP
+\fB\-m\fR, \fB\-\-max\-size\fR=\fInumber\fR
+Read form
+.I FILE
+only
+.I number
+of bytes. This option is meant to be used when reading additional
+randomness from a device.
+.IP
+The
+.I number
+argument may be followed by the multiplicative suffixes KiB=1024,
+MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is
+optional, e.g., "K" has the same meaning as "KiB") or the suffixes
+KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB.
+.TP
\fB\-v\fR, \fB\-\-verbose\fR
Inform where randomness originated, with amount of entropy read from each
source.
diff --git a/misc-utils/mcookie.c b/misc-utils/mcookie.c
index 31f33e4..caa1b8f 100644
--- a/misc-utils/mcookie.c
+++ b/misc-utils/mcookie.c
@@ -23,6 +23,7 @@
#include "nls.h"
#include "closestream.h"
#include "randutils.h"
+#include "strutils.h"
#include "xalloc.h"

#include <fcntl.h>
@@ -43,6 +44,7 @@ struct mcookie_control {
char **files;
int nfiles;
int fd;
+ uint64_t maxsz;
unsigned int
verbose:1;
};
@@ -50,11 +52,22 @@ struct mcookie_control {
/* The basic function to hash a file */
static size_t hash_file(struct mcookie_control *ctl)
{
- size_t count = 0;
- ssize_t r;
+ size_t count = 0, read_sz;
+ ssize_t r = 1;
unsigned char buf[BUFFERSIZE];
-
- while ((r = read(ctl->fd, buf, sizeof(buf))) > 0) {
+ int stop = 0;
+
+ read_sz = sizeof(buf);
+ while (!stop) {
+ if (ctl->maxsz) {
+ if (ctl->maxsz <= read_sz) {
+ read_sz = ctl->maxsz;
+ stop = 1;
+ } else
+ ctl->maxsz -= read_sz;
+ }
+ if ((r = read(ctl->fd, buf, read_sz)) == 0)
+ break;
MD5Update(&(ctl->ctx), buf, r);
count += r;
}
@@ -70,6 +83,7 @@ static void __attribute__((__noreturn__)) usage(FILE * out)
fprintf(out, _(" %s [options]\n"), program_invocation_short_name);
fputs(USAGE_OPTIONS, out);
fputs(_(" -f, --file <file> use file as a cookie seed\n"), out);
+ fputs(_(" -m, --max-size <num> limit how much is read from seed files\n"), out);
fputs(_(" -v, --verbose explain what is being done\n"), out);
fputs(USAGE_SEPARATOR, out);
fputs(USAGE_HELP, out);
@@ -117,6 +131,7 @@ int main(int argc, char **argv)

static const struct option longopts[] = {
{"file", required_argument, NULL, 'f'},
+ {"max-size", required_argument, NULL, 'm'},
{"verbose", no_argument, NULL, 'v'},
{"version", no_argument, NULL, 'V'},
{"help", no_argument, NULL, 'h'},
@@ -135,7 +150,7 @@ int main(int argc, char **argv)
ctl.files = xmalloc(sizeof(char *) * argc);

while ((c =
- getopt_long(argc, argv, "f:vVh", longopts, NULL)) != -1)
+ getopt_long(argc, argv, "f:m:vVh", longopts, NULL)) != -1)
switch (c) {
case 'v':
ctl.verbose = 1;
@@ -144,6 +159,10 @@ int main(int argc, char **argv)
ctl.files[ctl.nfiles] = optarg;
ctl.nfiles++;
break;
+ case 'm':
+ ctl.maxsz = strtosize_or_err(optarg,
+ _("failed to parse length"));
+ break;
case 'V':
printf(UTIL_LINUX_VERSION);
return EXIT_SUCCESS;
--
1.9.0