blob: a4be9d369638ba7252a30974568d02191b8ef70b [file] [log] [blame]
/* $OpenBSD: ssh-sk-helper.c,v 1.8 2020/01/10 23:43:26 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is a tiny program used to isolate the address space used for
* security key middleware signing operations from ssh-agent. It is similar
* to ssh-pkcs11-helper.c but considerably simpler as the operations for
* security keys are stateless.
*
* Please crank SSH_SK_HELPER_VERSION in sshkey.h for any incompatible
* protocol changes.
*/
#include "includes.h"
#include <limits.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include "xmalloc.h"
#include "log.h"
#include "sshkey.h"
#include "authfd.h"
#include "misc.h"
#include "sshbuf.h"
#include "msg.h"
#include "uidswap.h"
#include "sshkey.h"
#include "ssherr.h"
#include "ssh-sk.h"
#ifdef ENABLE_SK
extern char *__progname;
static struct sshbuf *reply_error(int r, char *fmt, ...)
__attribute__((__format__ (printf, 2, 3)));
static struct sshbuf *
reply_error(int r, char *fmt, ...)
{
char *msg;
va_list ap;
struct sshbuf *resp;
va_start(ap, fmt);
xvasprintf(&msg, fmt, ap);
va_end(ap);
error("%s: %s", __progname, msg);
free(msg);
if (r >= 0)
fatal("%s: invalid error code %d", __func__, r);
if ((resp = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if (sshbuf_put_u32(resp, SSH_SK_HELPER_ERROR) != 0 ||
sshbuf_put_u32(resp, (u_int)-r) != 0)
fatal("%s: buffer error", __progname);
return resp;
}
/* If the specified string is zero length, then free it and replace with NULL */
static void
null_empty(char **s)
{
if (s == NULL || *s == NULL || **s != '\0')
return;
free(*s);
*s = NULL;
}
static struct sshbuf *
process_sign(struct sshbuf *req)
{
int r = SSH_ERR_INTERNAL_ERROR;
struct sshbuf *resp, *kbuf;
struct sshkey *key;
uint32_t compat;
const u_char *message;
u_char *sig;
size_t msglen, siglen;
char *provider, *pin;
if ((r = sshbuf_froms(req, &kbuf)) != 0 ||
(r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
(r = sshbuf_get_string_direct(req, &message, &msglen)) != 0 ||
(r = sshbuf_get_cstring(req, NULL, NULL)) != 0 || /* alg */
(r = sshbuf_get_u32(req, &compat)) != 0 ||
(r = sshbuf_get_cstring(req, &pin, NULL)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (sshbuf_len(req) != 0)
fatal("%s: trailing data in request", __progname);
if ((r = sshkey_private_deserialize(kbuf, &key)) != 0)
fatal("Unable to parse private key: %s", ssh_err(r));
if (!sshkey_is_sk(key))
fatal("Unsupported key type %s", sshkey_ssh_name(key));
debug("%s: ready to sign with key %s, provider %s: "
"msg len %zu, compat 0x%lx", __progname, sshkey_type(key),
provider, msglen, (u_long)compat);
null_empty(&pin);
if ((r = sshsk_sign(provider, key, &sig, &siglen,
message, msglen, compat, pin)) != 0) {
resp = reply_error(r, "Signing failed: %s", ssh_err(r));
goto out;
}
if ((resp = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_SIGN)) != 0 ||
(r = sshbuf_put_string(resp, sig, siglen)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
out:
sshbuf_free(kbuf);
free(provider);
if (pin != NULL)
freezero(pin, strlen(pin));
return resp;
}
static struct sshbuf *
process_enroll(struct sshbuf *req)
{
int r;
u_int type;
char *provider, *application, *pin, *device, *userid;
uint8_t flags;
struct sshbuf *challenge, *attest, *kbuf, *resp;
struct sshkey *key;
if ((attest = sshbuf_new()) == NULL ||
(kbuf = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if ((r = sshbuf_get_u32(req, &type)) != 0 ||
(r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
(r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
(r = sshbuf_get_cstring(req, &application, NULL)) != 0 ||
(r = sshbuf_get_cstring(req, &userid, NULL)) != 0 ||
(r = sshbuf_get_u8(req, &flags)) != 0 ||
(r = sshbuf_get_cstring(req, &pin, NULL)) != 0 ||
(r = sshbuf_froms(req, &challenge)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (sshbuf_len(req) != 0)
fatal("%s: trailing data in request", __progname);
if (type > INT_MAX)
fatal("%s: bad type %u", __progname, type);
if (sshbuf_len(challenge) == 0) {
sshbuf_free(challenge);
challenge = NULL;
}
null_empty(&device);
null_empty(&userid);
null_empty(&pin);
if ((r = sshsk_enroll((int)type, provider, device, application, userid,
flags, pin, challenge, &key, attest)) != 0) {
resp = reply_error(r, "Enrollment failed: %s", ssh_err(r));
goto out;
}
if ((resp = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if ((r = sshkey_private_serialize(key, kbuf)) != 0)
fatal("%s: serialize private key: %s", __progname, ssh_err(r));
if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_ENROLL)) != 0 ||
(r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
(r = sshbuf_put_stringb(resp, attest)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
out:
sshkey_free(key);
sshbuf_free(kbuf);
sshbuf_free(attest);
sshbuf_free(challenge);
free(provider);
free(application);
if (pin != NULL)
freezero(pin, strlen(pin));
return resp;
}
static struct sshbuf *
process_load_resident(struct sshbuf *req)
{
int r;
char *provider, *pin, *device;
struct sshbuf *kbuf, *resp;
struct sshkey **keys = NULL;
size_t nkeys = 0, i;
if ((kbuf = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if ((r = sshbuf_get_cstring(req, &provider, NULL)) != 0 ||
(r = sshbuf_get_cstring(req, &device, NULL)) != 0 ||
(r = sshbuf_get_cstring(req, &pin, NULL)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (sshbuf_len(req) != 0)
fatal("%s: trailing data in request", __progname);
null_empty(&device);
null_empty(&pin);
if ((r = sshsk_load_resident(provider, device, pin,
&keys, &nkeys)) != 0) {
resp = reply_error(r, " sshsk_load_resident failed: %s",
ssh_err(r));
goto out;
}
if ((resp = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if ((r = sshbuf_put_u32(resp, SSH_SK_HELPER_LOAD_RESIDENT)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
for (i = 0; i < nkeys; i++) {
debug("%s: key %zu %s %s", __func__, i,
sshkey_type(keys[i]), keys[i]->sk_application);
sshbuf_reset(kbuf);
if ((r = sshkey_private_serialize(keys[i], kbuf)) != 0)
fatal("%s: serialize private key: %s",
__progname, ssh_err(r));
if ((r = sshbuf_put_stringb(resp, kbuf)) != 0 ||
(r = sshbuf_put_cstring(resp, "")) != 0) /* comment */
fatal("%s: buffer error: %s", __progname, ssh_err(r));
}
out:
for (i = 0; i < nkeys; i++)
sshkey_free(keys[i]);
free(keys);
sshbuf_free(kbuf);
free(provider);
if (pin != NULL)
freezero(pin, strlen(pin));
return resp;
}
int
main(int argc, char **argv)
{
SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
LogLevel log_level = SYSLOG_LEVEL_ERROR;
struct sshbuf *req, *resp;
int in, out, ch, r, vflag = 0;
u_int rtype, ll = 0;
uint8_t version, log_stderr = 0;
sanitise_stdfd();
log_init(__progname, log_level, log_facility, log_stderr);
while ((ch = getopt(argc, argv, "v")) != -1) {
switch (ch) {
case 'v':
vflag = 1;
if (log_level == SYSLOG_LEVEL_ERROR)
log_level = SYSLOG_LEVEL_DEBUG1;
else if (log_level < SYSLOG_LEVEL_DEBUG3)
log_level++;
break;
default:
fprintf(stderr, "usage: %s [-v]\n", __progname);
exit(1);
}
}
log_init(__progname, log_level, log_facility, vflag);
/*
* Rearrange our file descriptors a little; we don't trust the
* providers not to fiddle with stdin/out.
*/
closefrom(STDERR_FILENO + 1);
if ((in = dup(STDIN_FILENO)) == -1 || (out = dup(STDOUT_FILENO)) == -1)
fatal("%s: dup: %s", __progname, strerror(errno));
close(STDIN_FILENO);
close(STDOUT_FILENO);
sanitise_stdfd(); /* resets to /dev/null */
if ((req = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __progname);
if (ssh_msg_recv(in, req) < 0)
fatal("ssh_msg_recv failed");
close(in);
debug("%s: received message len %zu", __progname, sshbuf_len(req));
if ((r = sshbuf_get_u8(req, &version)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (version != SSH_SK_HELPER_VERSION) {
fatal("unsupported version: received %d, expected %d",
version, SSH_SK_HELPER_VERSION);
}
if ((r = sshbuf_get_u32(req, &rtype)) != 0 ||
(r = sshbuf_get_u8(req, &log_stderr)) != 0 ||
(r = sshbuf_get_u32(req, &ll)) != 0)
fatal("%s: buffer error: %s", __progname, ssh_err(r));
if (!vflag && log_level_name((LogLevel)ll) != NULL)
log_init(__progname, (LogLevel)ll, log_facility, log_stderr);
switch (rtype) {
case SSH_SK_HELPER_SIGN:
resp = process_sign(req);
break;
case SSH_SK_HELPER_ENROLL:
resp = process_enroll(req);
break;
case SSH_SK_HELPER_LOAD_RESIDENT:
resp = process_load_resident(req);
break;
default:
fatal("%s: unsupported request type %u", __progname, rtype);
}
sshbuf_free(req);
debug("%s: reply len %zu", __progname, sshbuf_len(resp));
if (ssh_msg_send(out, SSH_SK_HELPER_VERSION, resp) == -1)
fatal("ssh_msg_send failed");
sshbuf_free(resp);
close(out);
return (0);
}
#else /* ENABLE_SK */
#include <stdio.h>
int
main(int argc, char **argv)
{
fprintf(stderr, "ssh-sk-helper: disabled at compile time\n");
return -1;
}
#endif /* ENABLE_SK */