/* $OpenBSD: ssh-pkcs11-client.c,v 1.20 2024/08/15 00:51:51 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;
        if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
                error_f("sshkey_new failed");
                goto fail;
        }
        if ((key->pkey = EVP_PKEY_new()) == NULL ||
           EVP_PKEY_set1_RSA(key->pkey, rsa) != 1) {
                error_f("pkey setup failed");
                goto fail;
        }

        key->type = KEY_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);

        if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
                error_f("sshkey_new failed");
                goto fail;
        }
        if ((key->pkey = EVP_PKEY_new()) == NULL ||
            EVP_PKEY_set1_EC_KEY(key->pkey, ec) != 1) {
                error("pkey setup failed");
                goto fail;
        }
        if ((nid = sshkey_ecdsa_pkey_to_nid(key->pkey)) < 0) {
                error("couldn't get curve nid");
                goto fail;
        }
        key->ecdsa_nid = nid;
        key->type = KEY_ECDSA;

        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)
{
        RSA *rsa = NULL;
        EC_KEY *ecdsa = NULL;

        debug3_f("wrap %s for provider %s", sshkey_type(k), helper->path);
        if (k->type == KEY_RSA) {
                if ((rsa = EVP_PKEY_get1_RSA(k->pkey)) == NULL)
                        fatal_f("no RSA key");
                if (RSA_set_method(rsa, helper->rsa_meth) != 1)
                        fatal_f("RSA_set_method failed");
                if (helper->nrsa++ >= INT_MAX)
                        fatal_f("RSA refcount error");
                if (EVP_PKEY_set1_RSA(k->pkey, rsa) != 1)
                        fatal_f("EVP_PKEY_set1_RSA failed");
                RSA_free(rsa);
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
        } else if (k->type == KEY_ECDSA) {
                if ((ecdsa = EVP_PKEY_get1_EC_KEY(k->pkey)) == NULL)
                        fatal_f("no ECDSA key");
                if (EC_KEY_set_method(ecdsa, helper->ec_meth) != 1)
                        fatal_f("EC_KEY_set_method failed");
                if (helper->nec++ >= INT_MAX)
                        fatal_f("EC refcount error");
                if (EVP_PKEY_set1_EC_KEY(k->pkey, ecdsa) != 1)
                        fatal_f("EVP_PKEY_set1_EC_KEY failed");
                EC_KEY_free(ecdsa);
#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;
        RSA *rsa_priv = NULL, *rsa_cert = NULL;
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
        EC_KEY *ec_priv = NULL, *ec_cert = NULL;
#endif

        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 ((rsa_priv = EVP_PKEY_get1_RSA(priv->pkey)) == NULL)
                        fatal_f("no RSA pkey");
                if ((helper = helper_by_rsa(rsa_priv)) == 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");
                if ((rsa_cert = EVP_PKEY_get1_RSA(ret->pkey)) == NULL)
                        fatal_f("no RSA cert pkey");
                if (RSA_set_method(rsa_cert, helper->rsa_meth) != 1)
                        fatal_f("RSA_set_method failed");
                if (helper->nrsa++ >= INT_MAX)
                        fatal_f("RSA refcount error");
                if (EVP_PKEY_set1_RSA(ret->pkey, rsa_cert) != 1)
                        fatal_f("EVP_PKEY_set1_RSA failed");
                RSA_free(rsa_priv);
                RSA_free(rsa_cert);
#if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
        } else if (priv->type == KEY_ECDSA) {
                if ((ec_priv = EVP_PKEY_get1_EC_KEY(priv->pkey)) == NULL)
                        fatal_f("no EC pkey");
                if ((helper = helper_by_ec(ec_priv)) == 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");
                if ((ec_cert = EVP_PKEY_get1_EC_KEY(ret->pkey)) == NULL)
                        fatal_f("no EC cert pkey");
                if (EC_KEY_set_method(ec_cert, helper->ec_meth) != 1)
                        fatal_f("EC_KEY_set_method failed");
                if (helper->nec++ >= INT_MAX)
                        fatal_f("EC refcount error");
                if (EVP_PKEY_set1_EC_KEY(ret->pkey, ec_cert) != 1)
                        fatal_f("EVP_PKEY_set1_EC_KEY failed");
                EC_KEY_free(ec_priv);
                EC_KEY_free(ec_cert);
#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 = NULL;
        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 */