/* $NetBSD: ssh-pkcs11-client.c,v 1.15.2.1 2023/12/25 12:31:08 martin Exp $ */ /* $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" __RCSID("$NetBSD: ssh-pkcs11-client.c,v 1.15.2.1 2023/12/25 12:31:08 martin Exp $"); #include #include #include #include #include #include #include #include #include #include #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" /* 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; } 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 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), 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; } 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); } /* 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"); } 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); } /* * 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"); } 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"); } 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) { 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; RSA_METHOD *rsa_meth; EC_KEY_METHOD *ec_meth; 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"); 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]; const 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); 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)) { 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; }