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- /* $OpenBSD: ssh-pkcs11-client.c,v 1.19 2023/12/18 14:46:56 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 <limits.h>
-
- #include <openssl/ecdsa.h>
- #include <openssl/rsa.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"
-
- #include "openbsd-compat/openssl-compat.h"
-
- #if !defined(OPENSSL_HAS_ECC) || !defined(HAVE_EC_KEY_METHOD_NEW)
- #define EC_KEY_METHOD void
- #define EC_KEY void
- #endif
-
- /* borrows code from sftp-server and ssh-agent */
-
- /*
- * 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;
-
- }
-
- #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
- 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;
-
- }
- #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
-
- static void
- 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);
- #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
- EC_KEY_METHOD_free(helper->ec_meth);
- #endif
- 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),
- 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(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 */
- }
- len = PEEK_U32(buf);
- if (len > 256 * 1024)
- fatal("response too long: %u", len);
- /* read len bytes into 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)
- {
- return 0;
- }
-
- void
- pkcs11_terminate(void)
- {
- size_t i;
-
- debug3_f("terminating %zu helpers", nhelpers);
- for (i = 0; i < nhelpers; i++)
- helper_terminate(helpers[i]);
- }
-
- 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;
- 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);
- 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(helper->fd, msg);
- sshbuf_reset(msg);
-
- 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)) {
- memcpy(to, signature, slen);
- ret = slen;
- }
- free(signature);
- }
- fail:
- free(blob);
- sshkey_free(key);
- sshbuf_free(msg);
- return (ret);
- }
-
- 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;
- }
-
- #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;
- 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");
- 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(helper->fd, msg);
- sshbuf_reset(msg);
-
- 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;
- ret = d2i_ECDSA_SIG(NULL, &cp, slen);
- free(signature);
- }
-
- fail:
- free(blob);
- sshkey_free(key);
- sshbuf_free(msg);
- return (ret);
- }
-
- 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);
- }
- #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
-
- /* redirect private key crypto operations to the ssh-pkcs11-helper */
- static void
- wrap_key(struct helper *helper, struct sshkey *k)
- {
- 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");
- #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
- } 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");
- #endif
- } 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);
- }
-
- /*
- * Make a private PKCS#11-backed certificate by grafting a previously-loaded
- * PKCS#11 private key and a public certificate key.
- */
- int
- pkcs11_make_cert(const struct sshkey *priv,
- const struct sshkey *certpub, struct sshkey **certprivp)
- {
- struct helper *helper = NULL;
- struct sshkey *ret;
- int r;
-
- debug3_f("private key type %s cert type %s", sshkey_type(priv),
- sshkey_type(certpub));
- *certprivp = NULL;
- if (!sshkey_is_cert(certpub) || sshkey_is_cert(priv) ||
- !sshkey_equal_public(priv, certpub)) {
- error_f("private key %s doesn't match cert %s",
- sshkey_type(priv), sshkey_type(certpub));
- return SSH_ERR_INVALID_ARGUMENT;
- }
- *certprivp = NULL;
- if (priv->type == KEY_RSA) {
- if ((helper = helper_by_rsa(priv->rsa)) == NULL ||
- helper->fd == -1)
- fatal_f("no helper for PKCS11 RSA key");
- if ((r = sshkey_from_private(priv, &ret)) != 0)
- fatal_fr(r, "copy key");
- RSA_set_method(ret->rsa, helper->rsa_meth);
- if (helper->nrsa++ >= INT_MAX)
- fatal_f("RSA refcount error");
- #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
- } else if (priv->type == KEY_ECDSA) {
- if ((helper = helper_by_ec(priv->ecdsa)) == NULL ||
- helper->fd == -1)
- fatal_f("no helper for PKCS11 EC key");
- if ((r = sshkey_from_private(priv, &ret)) != 0)
- fatal_fr(r, "copy key");
- EC_KEY_set_method(ret->ecdsa, helper->ec_meth);
- if (helper->nec++ >= INT_MAX)
- fatal_f("EC refcount error");
- #endif
- } else
- fatal_f("unknown key type %s", sshkey_type(priv));
-
- ret->flags |= SSHKEY_FLAG_EXT;
- if ((r = sshkey_to_certified(ret)) != 0 ||
- (r = sshkey_cert_copy(certpub, ret)) != 0)
- fatal_fr(r, "graft certificate");
- debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
- helper->path, helper->nrsa, helper->nec);
- /* success */
- *certprivp = ret;
- return 0;
- }
-
- static int
- pkcs11_start_helper_methods(struct helper *helper)
- {
- RSA_METHOD *rsa_meth;
- EC_KEY_METHOD *ec_meth = NULL;
- #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
- 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 ((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);
- #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
-
- if ((rsa_meth = RSA_meth_dup(RSA_get_default_method())) == NULL)
- fatal_f("RSA_meth_dup failed");
- 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");
-
- helper->ec_meth = ec_meth;
- helper->rsa_meth = rsa_meth;
- return 0;
- }
-
- static struct helper *
- pkcs11_start_helper(const char *path)
- {
- int pair[2];
- 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_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_f("fork: %s", strerror(errno));
- fail:
- close(pair[0]);
- close(pair[1]);
- RSA_meth_free(helper->rsa_meth);
- #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
- EC_KEY_METHOD_free(helper->ec_meth);
- #endif
- free(helper);
- return NULL;
- } 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]);
- 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(prog, prog, verbosity, (char *)NULL);
- fprintf(stderr, "exec: %s: %s\n", prog, strerror(errno));
- _exit(1);
- }
- close(pair[1]);
- 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
- 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 helper *helper;
-
- 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");
- 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(helper->fd, msg);
- sshbuf_reset(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");
- *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(helper, 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;
- }
- sshbuf_free(msg);
- return (nkeys);
- }
-
- int
- pkcs11_del_provider(char *name)
- {
- struct helper *helper;
-
- /*
- * 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 */
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