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cmdgen: command-line control of PPK save parameters.

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This allows you to manually adjust the Argon2 parameters so that you
can trade off CPU requirements in legitimate use against difficulty of
brute-force attack. It also allows downgrading the key file version
back to the widespread PPK v2, so you can manually back-port a key
that you accidentally generated too new.
This commit is contained in:
Simon Tatham 2021-02-22 18:13:12 +00:00
parent b8f3fc4bd1
commit 117cee8ea6
1 changed files with 72 additions and 2 deletions
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74
cmdgen.c
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@ -150,6 +150,20 @@ void help(void)
" proven numbers that have been proven to be prime\n"
" proven-even also try harder for an even distribution\n"
" --strong-rsa use \"strong\" primes as RSA key factors\n"
" --ppk-param <key>=<value>[,<key>=<value>,...]\n"
" specify parameters when writing PuTTY private key file "
"format:\n"
" version PPK format version (min 2, max 3, "
"default 3)\n"
" memory Kb of memory to use in password hash "
"(default 8192)\n"
" time approx milliseconds to hash for "
"(default 100)\n"
" passes exact number of hash passes to run "
"(alternative to 'time')\n"
" parallelism number of parallelisable threads in the "
"hash function\n"
" (default 1)\n"
);
}
@ -227,6 +241,7 @@ int main(int argc, char **argv)
int exit_status = 0;
const PrimeGenerationPolicy *primegen = &primegen_probabilistic;
bool strong_rsa = false;
ppk_save_parameters params = ppk_save_default_parameters;
if (is_interactive())
progress_fp = stderr;
@ -366,6 +381,62 @@ int main(int argc, char **argv)
strong_rsa = true;
} else if (!strcmp(opt, "-reencrypt")) {
reencrypt = true;
} else if (!strcmp(opt, "-ppk-param") ||
!strcmp(opt, "-ppk-params")) {
if (!val && argc > 1)
--argc, val = *++argv;
if (!val) {
errs = true;
fprintf(stderr, "puttygen: option `-%s'"
" expects an argument\n", opt);
} else {
char *nextval;
for (; val; val = nextval) {
nextval = strchr(val, ',');
if (nextval)
*nextval++ = '\0';
char *optvalue = strchr(val, '=');
if (!optvalue) {
errs = true;
fprintf(stderr, "puttygen: PPK parameter "
"'%s' expected a value\n", val);
continue;
}
*optvalue++ = '\0';
char *end;
unsigned long n = strtoul(optvalue, &end, 0);
if (!*optvalue || *end) {
errs = true;
fprintf(stderr, "puttygen: value '%s' for "
"PPK parameter '%s': expected a "
"number\n", optvalue, val);
continue;
}
if (!strcmp(val, "version")) {
params.fmt_version = n;
} else if (!strcmp(val, "memory") ||
!strcmp(val, "mem")) {
params.argon2_mem = n;
} else if (!strcmp(val, "time")) {
params.argon2_passes_auto = true;
params.argon2_milliseconds = n;
} else if (!strcmp(val, "passes")) {
params.argon2_passes_auto = false;
params.argon2_milliseconds = n;
} else if (!strcmp(val, "parallelism") ||
!strcmp(val, "parallel")) {
params.argon2_parallelism = n;
} else {
errs = true;
fprintf(stderr, "puttygen: unrecognised "
"PPK parameter '%s'\n", val);
continue;
}
}
}
} else {
errs = true;
fprintf(stderr,
@ -1033,8 +1104,7 @@ int main(int argc, char **argv)
}
} else {
assert(ssh2key);
ret = ppk_save_f(outfilename, ssh2key, new_passphrase,
&ppk_save_default_parameters);
ret = ppk_save_f(outfilename, ssh2key, new_passphrase, &params);
if (!ret) {
fprintf(stderr, "puttygen: unable to save SSH-2 private key\n");
RETURN(1);