upstream: Separate ssh-pkcs11-helpers for each p11 module

Make ssh-pkcs11-client start an independent helper for each provider,
providing better isolation between modules and reliability if a single
module misbehaves.

This also implements reference counting of PKCS#11-hosted keys,
allowing ssh-pkcs11-helper subprocesses to be automatically reaped
when no remaining keys reference them. This fixes some bugs we have
that make PKCS11 keys unusable after they have been deleted, e.g.
https://bugzilla.mindrot.org/show_bug.cgi?id=3125

ok markus@

OpenBSD-Commit-ID: 0ce188b14fe271ab0568f4500070d96c5657244e
This commit is contained in:
djm@openbsd.org 2023-07-19 14:03:45 +00:00 committed by Damien Miller
parent 29ef8a0486
commit 099cdf59ce
No known key found for this signature in database
1 changed files with 283 additions and 91 deletions

View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-pkcs11-client.c,v 1.17 2020/10/18 11:32:02 djm Exp $ */
/* $OpenBSD: ssh-pkcs11-client.c,v 1.18 2023/07/19 14:03:45 djm Exp $ */
/*
* Copyright (c) 2010 Markus Friedl. All rights reserved.
* Copyright (c) 2014 Pedro Martelletto. All rights reserved.
@ -30,12 +30,11 @@
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <limits.h>
#include <openssl/ecdsa.h>
#include <openssl/rsa.h>
#include "openbsd-compat/openssl-compat.h"
#include "pathnames.h"
#include "xmalloc.h"
#include "sshbuf.h"
@ -47,18 +46,140 @@
#include "ssh-pkcs11.h"
#include "ssherr.h"
#include "openbsd-compat/openssl-compat.h"
/* borrows code from sftp-server and ssh-agent */
static int fd = -1;
static pid_t pid = -1;
/*
* Maintain a list of ssh-pkcs11-helper subprocesses. These may be looked up
* by provider path or their unique EC/RSA METHOD pointers.
*/
struct helper {
char *path;
pid_t pid;
int fd;
RSA_METHOD *rsa_meth;
EC_KEY_METHOD *ec_meth;
int (*rsa_finish)(RSA *rsa);
void (*ec_finish)(EC_KEY *key);
size_t nrsa, nec; /* number of active keys of each type */
};
static struct helper **helpers;
static size_t nhelpers;
static struct helper *
helper_by_provider(const char *path)
{
size_t i;
for (i = 0; i < nhelpers; i++) {
if (helpers[i] == NULL || helpers[i]->path == NULL ||
helpers[i]->fd == -1)
continue;
if (strcmp(helpers[i]->path, path) == 0)
return helpers[i];
}
return NULL;
}
static struct helper *
helper_by_rsa(const RSA *rsa)
{
size_t i;
const RSA_METHOD *meth;
if ((meth = RSA_get_method(rsa)) == NULL)
return NULL;
for (i = 0; i < nhelpers; i++) {
if (helpers[i] != NULL && helpers[i]->rsa_meth == meth)
return helpers[i];
}
return NULL;
}
static struct helper *
helper_by_ec(const EC_KEY *ec)
{
size_t i;
const EC_KEY_METHOD *meth;
if ((meth = EC_KEY_get_method(ec)) == NULL)
return NULL;
for (i = 0; i < nhelpers; i++) {
if (helpers[i] != NULL && helpers[i]->ec_meth == meth)
return helpers[i];
}
return NULL;
}
static void
send_msg(struct sshbuf *m)
helper_free(struct helper *helper)
{
size_t i;
int found = 0;
if (helper == NULL)
return;
if (helper->path == NULL || helper->ec_meth == NULL ||
helper->rsa_meth == NULL)
fatal_f("inconsistent helper");
debug3_f("free helper for provider %s", helper->path);
for (i = 0; i < nhelpers; i++) {
if (helpers[i] == helper) {
if (found)
fatal_f("helper recorded more than once");
found = 1;
}
else if (found)
helpers[i - 1] = helpers[i];
}
if (found) {
helpers = xrecallocarray(helpers, nhelpers,
nhelpers - 1, sizeof(*helpers));
nhelpers--;
}
free(helper->path);
EC_KEY_METHOD_free(helper->ec_meth);
RSA_meth_free(helper->rsa_meth);
free(helper);
}
static void
helper_terminate(struct helper *helper)
{
if (helper == NULL) {
return;
} else if (helper->fd == -1) {
debug3_f("already terminated");
} else {
debug3_f("terminating helper for %s; "
"remaining %zu RSA %zu ECDSA",
helper->path, helper->nrsa, helper->nec);
close(helper->fd);
/* XXX waitpid() */
helper->fd = -1;
helper->pid = -1;
}
/*
* Don't delete the helper entry until there are no remaining keys
* that reference it. Otherwise, any signing operation would call
* a free'd METHOD pointer and that would be bad.
*/
if (helper->nrsa == 0 && helper->nec == 0)
helper_free(helper);
}
static void
send_msg(int fd, struct sshbuf *m)
{
u_char buf[4];
size_t mlen = sshbuf_len(m);
int r;
if (fd == -1)
return;
POKE_U32(buf, mlen);
if (atomicio(vwrite, fd, buf, 4) != 4 ||
atomicio(vwrite, fd, sshbuf_mutable_ptr(m),
@ -69,12 +190,15 @@ send_msg(struct sshbuf *m)
}
static int
recv_msg(struct sshbuf *m)
recv_msg(int fd, struct sshbuf *m)
{
u_int l, len;
u_char c, buf[1024];
int r;
sshbuf_reset(m);
if (fd == -1)
return 0; /* XXX */
if ((len = atomicio(read, fd, buf, 4)) != 4) {
error("read from helper failed: %u", len);
return (0); /* XXX */
@ -83,7 +207,6 @@ recv_msg(struct sshbuf *m)
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))
@ -104,14 +227,17 @@ recv_msg(struct sshbuf *m)
int
pkcs11_init(int interactive)
{
return (0);
return 0;
}
void
pkcs11_terminate(void)
{
if (fd >= 0)
close(fd);
size_t i;
debug3_f("terminating %zu helpers", nhelpers);
for (i = 0; i < nhelpers; i++)
helper_terminate(helpers[i]);
}
static int
@ -122,7 +248,11 @@ rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
u_char *blob = NULL, *signature = NULL;
size_t blen, slen = 0;
int r, ret = -1;
struct helper *helper;
if ((helper = helper_by_rsa(rsa)) == NULL || helper->fd == -1)
fatal_f("no helper for PKCS11 key");
debug3_f("signing with PKCS11 provider %s", helper->path);
if (padding != RSA_PKCS1_PADDING)
goto fail;
key = sshkey_new(KEY_UNSPEC);
@ -144,10 +274,10 @@ rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
(r = sshbuf_put_string(msg, from, flen)) != 0 ||
(r = sshbuf_put_u32(msg, 0)) != 0)
fatal_fr(r, "compose");
send_msg(msg);
send_msg(helper->fd, msg);
sshbuf_reset(msg);
if (recv_msg(msg) == SSH2_AGENT_SIGN_RESPONSE) {
if (recv_msg(helper->fd, 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)) {
@ -163,7 +293,26 @@ rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
return (ret);
}
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
static int
rsa_finish(RSA *rsa)
{
struct helper *helper;
if ((helper = helper_by_rsa(rsa)) == NULL)
fatal_f("no helper for PKCS11 key");
debug3_f("free PKCS11 RSA key for provider %s", helper->path);
if (helper->rsa_finish != NULL)
helper->rsa_finish(rsa);
if (helper->nrsa == 0)
fatal_f("RSA refcount error");
helper->nrsa--;
debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
helper->path, helper->nrsa, helper->nec);
if (helper->nrsa == 0 && helper->nec == 0)
helper_terminate(helper);
return 1;
}
static ECDSA_SIG *
ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
const BIGNUM *rp, EC_KEY *ec)
@ -175,7 +324,11 @@ ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
u_char *blob = NULL, *signature = NULL;
size_t blen, slen = 0;
int r, nid;
struct helper *helper;
if ((helper = helper_by_ec(ec)) == NULL || helper->fd == -1)
fatal_f("no helper for PKCS11 key");
debug3_f("signing with PKCS11 provider %s", helper->path);
nid = sshkey_ecdsa_key_to_nid(ec);
if (nid < 0) {
error_f("couldn't get curve nid");
@ -203,10 +356,10 @@ ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
(r = sshbuf_put_string(msg, dgst, dgst_len)) != 0 ||
(r = sshbuf_put_u32(msg, 0)) != 0)
fatal_fr(r, "compose");
send_msg(msg);
send_msg(helper->fd, msg);
sshbuf_reset(msg);
if (recv_msg(msg) == SSH2_AGENT_SIGN_RESPONSE) {
if (recv_msg(helper->fd, msg) == SSH2_AGENT_SIGN_RESPONSE) {
if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
fatal_fr(r, "parse");
cp = signature;
@ -220,75 +373,110 @@ ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
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 */
static void
ecdsa_do_finish(EC_KEY *ec)
{
struct helper *helper;
if ((helper = helper_by_ec(ec)) == NULL)
fatal_f("no helper for PKCS11 key");
debug3_f("free PKCS11 ECDSA key for provider %s", helper->path);
if (helper->ec_finish != NULL)
helper->ec_finish(ec);
if (helper->nec == 0)
fatal_f("ECDSA refcount error");
helper->nec--;
debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
helper->path, helper->nrsa, helper->nec);
if (helper->nrsa == 0 && helper->nec == 0)
helper_terminate(helper);
}
/* redirect private key crypto operations to the ssh-pkcs11-helper */
static void
wrap_key(struct sshkey *k)
wrap_key(struct helper *helper, 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
debug3_f("wrap %s for provider %s", sshkey_type(k), helper->path);
if (k->type == KEY_RSA) {
RSA_set_method(k->rsa, helper->rsa_meth);
if (helper->nrsa++ >= INT_MAX)
fatal_f("RSA refcount error");
} else if (k->type == KEY_ECDSA) {
EC_KEY_set_method(k->ecdsa, helper->ec_meth);
if (helper->nec++ >= INT_MAX)
fatal_f("EC refcount error");
} else
fatal_f("unknown key type");
k->flags |= SSHKEY_FLAG_EXT;
debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
helper->path, helper->nrsa, helper->nec);
}
static int
pkcs11_start_helper_methods(void)
pkcs11_start_helper_methods(struct helper *helper)
{
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 *,
int (*ec_init)(EC_KEY *key);
int (*ec_copy)(EC_KEY *dest, const EC_KEY *src);
int (*ec_set_group)(EC_KEY *key, const EC_GROUP *grp);
int (*ec_set_private)(EC_KEY *key, const BIGNUM *priv_key);
int (*ec_set_public)(EC_KEY *key, const EC_POINT *pub_key);
int (*ec_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 */
RSA_METHOD *rsa_meth;
EC_KEY_METHOD *ec_meth;
if ((helper_rsa = RSA_meth_dup(RSA_get_default_method())) == NULL)
if ((ec_meth = EC_KEY_METHOD_new(EC_KEY_OpenSSL())) == NULL)
return -1;
EC_KEY_METHOD_get_sign(ec_meth, &ec_sign, NULL, NULL);
EC_KEY_METHOD_set_sign(ec_meth, ec_sign, NULL, ecdsa_do_sign);
EC_KEY_METHOD_get_init(ec_meth, &ec_init, &helper->ec_finish,
&ec_copy, &ec_set_group, &ec_set_private, &ec_set_public);
EC_KEY_METHOD_set_init(ec_meth, ec_init, ecdsa_do_finish,
ec_copy, ec_set_group, ec_set_private, ec_set_public);
if ((rsa_meth = 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))
helper->rsa_finish = RSA_meth_get_finish(rsa_meth);
if (!RSA_meth_set1_name(rsa_meth, "ssh-pkcs11-helper") ||
!RSA_meth_set_priv_enc(rsa_meth, rsa_encrypt) ||
!RSA_meth_set_finish(rsa_meth, rsa_finish))
fatal_f("failed to prepare method");
return (0);
helper->ec_meth = ec_meth;
helper->rsa_meth = rsa_meth;
return 0;
}
static int
pkcs11_start_helper(void)
static struct helper *
pkcs11_start_helper(const char *path)
{
int pair[2];
char *helper, *verbosity = NULL;
if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)
verbosity = "-vvv";
if (pkcs11_start_helper_methods() == -1) {
error("pkcs11_start_helper_methods failed");
return (-1);
}
char *prog, *verbosity = NULL;
struct helper *helper;
pid_t pid;
if (nhelpers >= INT_MAX)
fatal_f("too many helpers");
debug3_f("start helper for %s", path);
if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
error("socketpair: %s", strerror(errno));
return (-1);
error_f("socketpair: %s", strerror(errno));
return NULL;
}
helper = xcalloc(1, sizeof(*helper));
if (pkcs11_start_helper_methods(helper) == -1) {
error_f("pkcs11_start_helper_methods failed");
goto fail;
}
if ((pid = fork()) == -1) {
error("fork: %s", strerror(errno));
return (-1);
error_f("fork: %s", strerror(errno));
fail:
close(pair[0]);
close(pair[1]);
RSA_meth_free(helper->rsa_meth);
EC_KEY_METHOD_free(helper->ec_meth);
free(helper);
return NULL;
} else if (pid == 0) {
if ((dup2(pair[1], STDIN_FILENO) == -1) ||
(dup2(pair[1], STDOUT_FILENO) == -1)) {
@ -297,18 +485,27 @@ pkcs11_start_helper(void)
}
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,
prog = getenv("SSH_PKCS11_HELPER");
if (prog == NULL || strlen(prog) == 0)
prog = _PATH_SSH_PKCS11_HELPER;
if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)
verbosity = "-vvv";
debug_f("starting %s %s", prog,
verbosity == NULL ? "" : verbosity);
execlp(helper, helper, verbosity, (char *)NULL);
fprintf(stderr, "exec: %s: %s\n", helper, strerror(errno));
execlp(prog, prog, verbosity, (char *)NULL);
fprintf(stderr, "exec: %s: %s\n", prog, strerror(errno));
_exit(1);
}
close(pair[1]);
fd = pair[0];
return (0);
helper->fd = pair[0];
helper->path = xstrdup(path);
helper->pid = pid;
debug3_f("helper %zu for \"%s\" on fd %d pid %ld", nhelpers,
helper->path, helper->fd, (long)helper->pid);
helpers = xrecallocarray(helpers, nhelpers,
nhelpers + 1, sizeof(*helpers));
helpers[nhelpers++] = helper;
return helper;
}
int
@ -322,9 +519,11 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
size_t blen;
u_int nkeys, i;
struct sshbuf *msg;
struct helper *helper;
if (fd < 0 && pkcs11_start_helper() < 0)
return (-1);
if ((helper = helper_by_provider(name)) == NULL &&
(helper = pkcs11_start_helper(name)) == NULL)
return -1;
if ((msg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
@ -332,10 +531,10 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
(r = sshbuf_put_cstring(msg, name)) != 0 ||
(r = sshbuf_put_cstring(msg, pin)) != 0)
fatal_fr(r, "compose");
send_msg(msg);
send_msg(helper->fd, msg);
sshbuf_reset(msg);
type = recv_msg(msg);
type = recv_msg(helper->fd, msg);
if (type == SSH2_AGENT_IDENTITIES_ANSWER) {
if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
fatal_fr(r, "parse nkeys");
@ -349,7 +548,7 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
fatal_fr(r, "parse key");
if ((r = sshkey_from_blob(blob, blen, &k)) != 0)
fatal_fr(r, "decode key");
wrap_key(k);
wrap_key(helper, k);
(*keysp)[i] = k;
if (labelsp)
(*labelsp)[i] = label;
@ -370,22 +569,15 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
int
pkcs11_del_provider(char *name)
{
int r, ret = -1;
struct sshbuf *msg;
struct helper *helper;
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);
/*
* ssh-agent deletes keys before calling this, so the helper entry
* should be gone before we get here.
*/
debug3_f("delete %s", name);
if ((helper = helper_by_provider(name)) != NULL)
helper_terminate(helper);
return 0;
}
#endif /* ENABLE_PKCS11 */