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cmdgen: option to specify the random number device to use.

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E.g. you might pass '--random-device=/dev/urandom'.

Mostly because I got sick of waiting for /dev/random to finish
blocking while I was trying to generate throwaway keys for testing bug
fixes in cmdgen itself. But it might also be useful on systems that
call their random device by a different name that we haven't
encountered.

(Since cmdgen also reads the saved PuTTY random seed file, setting
this option to /dev/zero will not render key generation deterministic.
It's tempting to provide _some_ way to do that, for testing purposes
and clearly marked as dangerous of course, but I think it would take
more faff than this.)
This commit is contained in:
Simon Tatham
2016-03-30 08:17:03 +01:00
parent ad87950539
commit 435b29da88
3 changed files with 27 additions and 7 deletions
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17
cmdgen.c
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@ -37,7 +37,7 @@
* run tests.
*/
#define get_random_data get_random_data_diagnostic
char *get_random_data(int len)
char *get_random_data(int len, const char *device)
{
char *buf = snewn(len, char);
memset(buf, 'x', len);
@ -177,6 +177,8 @@ void help(void)
" specify file containing old key passphrase\n"
" --new-passphrase file\n"
" specify file containing new key passphrase\n"
" --random-device device\n"
" specify device to read entropy from (e.g. /dev/urandom)\n"
);
}
@ -245,6 +247,7 @@ int main(int argc, char **argv)
char *old_passphrase = NULL, *new_passphrase = NULL;
int load_encrypted;
progfn_t progressfn = is_interactive() ? progress_update : no_progress;
const char *random_device = NULL;
/* ------------------------------------------------------------------
* Parse the command line to figure out what we've been asked to do.
@ -338,6 +341,16 @@ int main(int argc, char **argv)
if (!new_passphrase)
errs = TRUE;
}
} else if (!strcmp(opt, "-random-device")) {
if (!val && argc > 1)
--argc, val = *++argv;
if (!val) {
errs = TRUE;
fprintf(stderr, "puttygen: option `-%s'"
" expects an argument\n", opt);
} else {
random_device = val;
}
} else {
errs = TRUE;
fprintf(stderr,
@ -677,7 +690,7 @@ int main(int argc, char **argv)
strftime(default_comment, 30, "rsa-key-%Y%m%d", &tm);
random_ref();
entropy = get_random_data(bits / 8);
entropy = get_random_data(bits / 8, random_device);
if (!entropy) {
fprintf(stderr, "puttygen: failed to collect entropy, "
"could not generate key\n");