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openssh-portable/ssh-pkcs11-client.c

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/* $OpenBSD: ssh-pkcs11-client.c,v 1.17 2020/10/18 11:32:02 djm Exp $ */
/*
* Copyright (c) 2010 Markus Friedl. All rights reserved.
* Copyright (c) 2014 Pedro Martelletto. All rights reserved.
*
* 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.
*/
#include "includes.h"
#ifdef ENABLE_PKCS11
#include <sys/types.h>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include <sys/socket.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <openssl/ecdsa.h>
#include <openssl/rsa.h>
#include "openbsd-compat/openssl-compat.h"
#include "pathnames.h"
#include "xmalloc.h"
#include "sshbuf.h"
#include "log.h"
#include "misc.h"
#include "sshkey.h"
#include "authfd.h"
#include "atomicio.h"
#include "ssh-pkcs11.h"
#include "ssherr.h"
#ifdef WINDOWS
#include "openbsd-compat/sys-queue.h"
#define CRYPTOKI_COMPAT
#include "pkcs11.h"
static char module_path[PATH_MAX + 1];
extern char* sshagent_con_username;
extern HANDLE sshagent_client_primary_token;
struct pkcs11_provider {
char *name;
TAILQ_ENTRY(pkcs11_provider) next;
};
TAILQ_HEAD(, pkcs11_provider) pkcs11_providers;
struct pkcs11_keyinfo {
struct sshkey *key;
char *providername, *label;
TAILQ_ENTRY(pkcs11_keyinfo) next;
};
TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
#define MAX_MSG_LENGTH 10240 /*XXX*/
/* input and output queue */
struct sshbuf *iqueue;
struct sshbuf *oqueue;
void
add_key(struct sshkey *k, char *name)
{
struct pkcs11_keyinfo *ki;
ki = xcalloc(1, sizeof(*ki));
ki->providername = xstrdup(name);
ki->key = k;
TAILQ_INSERT_TAIL(&pkcs11_keylist, ki, next);
}
void
del_all_keys()
{
struct pkcs11_keyinfo *ki, *nxt;
for (ki = TAILQ_FIRST(&pkcs11_keylist); ki; ki = nxt) {
nxt = TAILQ_NEXT(ki, next);
TAILQ_REMOVE(&pkcs11_keylist, ki, next);
free(ki->providername);
sshkey_free(ki->key);
free(ki);
}
}
/* lookup matching 'private' key */
struct sshkey *
lookup_key(const struct sshkey *k)
{
struct pkcs11_keyinfo *ki;
TAILQ_FOREACH(ki, &pkcs11_keylist, next) {
debug("check %p %s %s", ki, ki->providername, ki->label);
if (sshkey_equal(k, ki->key))
return (ki->key);
}
return (NULL);
}
static char *
find_helper_in_module_path(void)
{
wchar_t path[PATH_MAX + 1];
DWORD n;
char *ep;
memset(module_path, 0, sizeof(module_path));
memset(path, 0, sizeof(path));
if ((n = GetModuleFileNameW(NULL, path, PATH_MAX)) == 0 ||
n >= PATH_MAX) {
error_f("GetModuleFileNameW failed");
return NULL;
}
if (wcstombs_s(NULL, module_path, sizeof(module_path), path,
sizeof(module_path) - 1) != 0) {
error_f("wcstombs_s failed");
return NULL;
}
if ((ep = strrchr(module_path, '\\')) == NULL) {
error_f("couldn't locate trailing \\");
return NULL;
}
*(++ep) = '\0'; /* trim */
strlcat(module_path, "ssh-pkcs11-helper.exe", sizeof(module_path) - 1);
return module_path;
}
static char *
find_helper(void)
{
char *helper;
char module_path[PATH_MAX + 1];
char *ep;
DWORD n;
if ((helper = getenv("SSH_PKCS11_HELPER")) == NULL || strlen(helper) == 0) {
if ((helper = find_helper_in_module_path()) == NULL)
helper = _PATH_SSH_PKCS11_HELPER;
}
if (!path_absolute(helper)) {
error_f("helper \"%s\" unusable: path not absolute", helper);
return NULL;
}
debug_f("using \"%s\" as helper", helper);
return helper;
}
#endif /* WINDOWS */
/* borrows code from sftp-server and ssh-agent */
static int fd = -1;
static pid_t pid = -1;
static void
send_msg(struct sshbuf *m)
{
u_char buf[4];
size_t mlen = sshbuf_len(m);
int r;
POKE_U32(buf, mlen);
if (atomicio(vwrite, fd, buf, 4) != 4 ||
atomicio(vwrite, fd, sshbuf_mutable_ptr(m),
sshbuf_len(m)) != sshbuf_len(m))
error("write to helper failed");
if ((r = sshbuf_consume(m, mlen)) != 0)
fatal_fr(r, "consume");
}
static int
recv_msg(struct sshbuf *m)
{
u_int l, len;
u_char c, buf[1024];
int r;
if ((len = atomicio(read, fd, buf, 4)) != 4) {
error("read from helper failed: %u", len);
return (0); /* XXX */
}
len = PEEK_U32(buf);
if (len > 256 * 1024)
fatal("response too long: %u", len);
/* read len bytes into m */
sshbuf_reset(m);
while (len > 0) {
l = len;
if (l > sizeof(buf))
l = sizeof(buf);
if (atomicio(read, fd, buf, l) != l) {
error("response from helper failed.");
return (0); /* XXX */
}
if ((r = sshbuf_put(m, buf, l)) != 0)
fatal_fr(r, "sshbuf_put");
len -= l;
}
if ((r = sshbuf_get_u8(m, &c)) != 0)
fatal_fr(r, "parse type");
return c;
}
int
pkcs11_init(int interactive)
{
#ifdef WINDOWS
TAILQ_INIT(&pkcs11_providers);
TAILQ_INIT(&pkcs11_keylist);
#endif /* WINDOWS */
return (0);
}
void
pkcs11_terminate(void)
{
#ifdef WINDOWS
struct pkcs11_provider *p;
while ((p = TAILQ_FIRST(&pkcs11_providers)) != NULL) {
// Send message to helper to gracefully unload providers
pkcs11_del_provider(p->name);
TAILQ_REMOVE(&pkcs11_providers, p, next);
}
if (pid != -1) {
kill(pid, SIGTERM);
waitpid(pid, NULL, 0);
pid = -1;
}
#endif /* WINDOWS */
if (fd >= 0)
close(fd);
#ifdef WINDOWS
fd = -1;
#endif
}
static int
rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
{
struct sshkey *key = NULL;
struct sshbuf *msg = NULL;
u_char *blob = NULL, *signature = NULL;
size_t blen, slen = 0;
int r, ret = -1;
if (padding != RSA_PKCS1_PADDING)
goto fail;
key = sshkey_new(KEY_UNSPEC);
if (key == NULL) {
error_f("sshkey_new failed");
goto fail;
}
key->type = KEY_RSA;
RSA_up_ref(rsa);
key->rsa = rsa;
if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
error_fr(r, "encode key");
goto fail;
}
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
(r = sshbuf_put_string(msg, blob, blen)) != 0 ||
(r = sshbuf_put_string(msg, from, flen)) != 0 ||
(r = sshbuf_put_u32(msg, 0)) != 0)
fatal_fr(r, "compose");
send_msg(msg);
sshbuf_reset(msg);
if (recv_msg(msg) == SSH2_AGENT_SIGN_RESPONSE) {
if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
fatal_fr(r, "parse");
if (slen <= (size_t)RSA_size(rsa)) {
memcpy(to, signature, slen);
ret = slen;
}
free(signature);
}
fail:
free(blob);
sshkey_free(key);
sshbuf_free(msg);
return (ret);
}
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
static ECDSA_SIG *
ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
const BIGNUM *rp, EC_KEY *ec)
{
struct sshkey *key = NULL;
struct sshbuf *msg = NULL;
ECDSA_SIG *ret = NULL;
const u_char *cp;
u_char *blob = NULL, *signature = NULL;
size_t blen, slen = 0;
int r, nid;
nid = sshkey_ecdsa_key_to_nid(ec);
if (nid < 0) {
error_f("couldn't get curve nid");
goto fail;
}
key = sshkey_new(KEY_UNSPEC);
if (key == NULL) {
error_f("sshkey_new failed");
goto fail;
}
key->ecdsa = ec;
key->ecdsa_nid = nid;
key->type = KEY_ECDSA;
EC_KEY_up_ref(ec);
if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
error_fr(r, "encode key");
goto fail;
}
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
(r = sshbuf_put_string(msg, blob, blen)) != 0 ||
(r = sshbuf_put_string(msg, dgst, dgst_len)) != 0 ||
(r = sshbuf_put_u32(msg, 0)) != 0)
fatal_fr(r, "compose");
send_msg(msg);
sshbuf_reset(msg);
if (recv_msg(msg) == SSH2_AGENT_SIGN_RESPONSE) {
if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
fatal_fr(r, "parse");
cp = signature;
ret = d2i_ECDSA_SIG(NULL, &cp, slen);
free(signature);
}
fail:
free(blob);
sshkey_free(key);
sshbuf_free(msg);
return (ret);
}
#endif /* OPENSSL_HAS_ECC && HAVE_EC_KEY_METHOD_NEW */
static RSA_METHOD *helper_rsa;
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
static EC_KEY_METHOD *helper_ecdsa;
#endif /* OPENSSL_HAS_ECC && HAVE_EC_KEY_METHOD_NEW */
/* redirect private key crypto operations to the ssh-pkcs11-helper */
static void
wrap_key(struct sshkey *k)
{
if (k->type == KEY_RSA)
RSA_set_method(k->rsa, helper_rsa);
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
else if (k->type == KEY_ECDSA)
EC_KEY_set_method(k->ecdsa, helper_ecdsa);
#endif /* OPENSSL_HAS_ECC && HAVE_EC_KEY_METHOD_NEW */
else
fatal_f("unknown key type");
}
static int
pkcs11_start_helper_methods(void)
{
if (helper_rsa != NULL)
return (0);
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
int (*orig_sign)(int, const unsigned char *, int, unsigned char *,
unsigned int *, const BIGNUM *, const BIGNUM *, EC_KEY *) = NULL;
if (helper_ecdsa != NULL)
return (0);
helper_ecdsa = EC_KEY_METHOD_new(EC_KEY_OpenSSL());
if (helper_ecdsa == NULL)
return (-1);
EC_KEY_METHOD_get_sign(helper_ecdsa, &orig_sign, NULL, NULL);
EC_KEY_METHOD_set_sign(helper_ecdsa, orig_sign, NULL, ecdsa_do_sign);
#endif /* OPENSSL_HAS_ECC && HAVE_EC_KEY_METHOD_NEW */
if ((helper_rsa = RSA_meth_dup(RSA_get_default_method())) == NULL)
fatal_f("RSA_meth_dup failed");
if (!RSA_meth_set1_name(helper_rsa, "ssh-pkcs11-helper") ||
!RSA_meth_set_priv_enc(helper_rsa, rsa_encrypt))
fatal_f("failed to prepare method");
return (0);
}
static int
pkcs11_start_helper(void)
{
int pair[2];
char *helper, *verbosity = NULL;
#ifdef WINDOWS
int r, actions_inited = 0;
char *av[3];
posix_spawn_file_actions_t actions;
HANDLE client_token = NULL, client_process_handle = NULL;
r = SSH_ERR_SYSTEM_ERROR;
pair[0] = pair[1] = -1;
if ((helper = find_helper()) == NULL)
goto out;
#endif /* WINDOWS */
#ifdef DEBUG_PKCS11
verbosity = "-vvv";
#endif
if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)
verbosity = "-vvv";
if (pkcs11_start_helper_methods() == -1) {
error("pkcs11_start_helper_methods failed");
return (-1);
}
if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
error("socketpair: %s", strerror(errno));
return (-1);
}
#ifdef WINDOWS
if (posix_spawn_file_actions_init(&actions) != 0) {
error_f("posix_spawn_file_actions_init failed");
goto out;
}
actions_inited = 1;
if (posix_spawn_file_actions_adddup2(&actions, pair[1],
STDIN_FILENO) != 0 ||
posix_spawn_file_actions_adddup2(&actions, pair[1],
STDOUT_FILENO) != 0) {
error_f("posix_spawn_file_actions_adddup2 failed");
goto out;
}
av[0] = helper;
av[1] = verbosity;
av[2] = NULL;
if (!sshagent_con_username) {
error_f("sshagent_con_username is NULL");
goto out;
}
if (!sshagent_client_primary_token) {
error_f("sshagent_client_primary_token is NULL for user:%s", sshagent_con_username);
goto out;
}
if (posix_spawnp_as_user((pid_t *)&pid, av[0], &actions, NULL, av, NULL, sshagent_client_primary_token) != 0) {
error_f("failed to spwan process %s", av[0]);
goto out;
}
fd = pair[0];
r = 0;
#else
if ((pid = fork()) == -1) {
error("fork: %s", strerror(errno));
return (-1);
} else if (pid == 0) {
if ((dup2(pair[1], STDIN_FILENO) == -1) ||
(dup2(pair[1], STDOUT_FILENO) == -1)) {
fprintf(stderr, "dup2: %s\n", strerror(errno));
_exit(1);
}
close(pair[0]);
close(pair[1]);
helper = getenv("SSH_PKCS11_HELPER");
if (helper == NULL || strlen(helper) == 0)
helper = _PATH_SSH_PKCS11_HELPER;
debug_f("starting %s %s", helper,
verbosity == NULL ? "" : verbosity);
execlp(helper, helper, verbosity, (char *)NULL);
fprintf(stderr, "exec: %s: %s\n", helper, strerror(errno));
_exit(1);
}
close(pair[1]);
fd = pair[0];
return (0);
#endif
/* success */
debug3_f("started pid=%ld", (long)pid);
out:
if (client_token)
CloseHandle(client_token);
return r;
}
int
pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
char ***labelsp)
{
struct sshkey *k;
int r, type;
u_char *blob;
char *label;
size_t blen;
u_int nkeys, i;
struct sshbuf *msg;
struct pkcs11_provider *p;
if (fd < 0 && pkcs11_start_helper() < 0)
return (-1);
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshbuf_put_u8(msg, SSH_AGENTC_ADD_SMARTCARD_KEY)) != 0 ||
(r = sshbuf_put_cstring(msg, name)) != 0 ||
(r = sshbuf_put_cstring(msg, pin)) != 0)
fatal_fr(r, "compose");
send_msg(msg);
sshbuf_reset(msg);
type = recv_msg(msg);
if (type == SSH2_AGENT_IDENTITIES_ANSWER) {
if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
fatal_fr(r, "parse nkeys");
*keysp = xcalloc(nkeys, sizeof(struct sshkey *));
if (labelsp)
*labelsp = xcalloc(nkeys, sizeof(char *));
for (i = 0; i < nkeys; i++) {
/* XXX clean up properly instead of fatal() */
if ((r = sshbuf_get_string(msg, &blob, &blen)) != 0 ||
(r = sshbuf_get_cstring(msg, &label, NULL)) != 0)
fatal_fr(r, "parse key");
if ((r = sshkey_from_blob(blob, blen, &k)) != 0)
fatal_fr(r, "decode key");
wrap_key(k);
(*keysp)[i] = k;
if (labelsp)
(*labelsp)[i] = label;
else
free(label);
free(blob);
}
} else if (type == SSH2_AGENT_FAILURE) {
if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
nkeys = -1;
} else {
nkeys = -1;
}
#ifdef WINDOWS
p = xcalloc(1, sizeof(*p));
p->name = xstrdup(name);
TAILQ_INSERT_TAIL(&pkcs11_providers, p, next);
#endif /* WINDOWS */
sshbuf_free(msg);
return (nkeys);
}
int
pkcs11_del_provider(char *name)
{
int r, ret = -1;
struct sshbuf *msg;
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshbuf_put_u8(msg, SSH_AGENTC_REMOVE_SMARTCARD_KEY)) != 0 ||
(r = sshbuf_put_cstring(msg, name)) != 0 ||
(r = sshbuf_put_cstring(msg, "")) != 0)
fatal_fr(r, "compose");
send_msg(msg);
sshbuf_reset(msg);
if (recv_msg(msg) == SSH_AGENT_SUCCESS)
ret = 0;
sshbuf_free(msg);
return (ret);
}
#endif /* ENABLE_PKCS11 */
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