/* $OpenBSD: ssh-pkcs11-client.c,v 1.26 2026/02/09 22:11:39 dtucker 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 <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>

#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <limits.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"

/* 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 keyblobs.
 */
struct helper {
        char *path;
        pid_t pid;
        int fd;
        size_t nkeyblobs;
        struct sshbuf **keyblobs; /* XXX use a tree or something faster */
};
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_key(const struct sshkey *key)
{
        size_t i, j;
        struct sshbuf *keyblob = NULL;
        int r;

        if ((keyblob = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new failed");
        if ((r = sshkey_putb(key, keyblob)) != 0)
                fatal_fr(r, "serialise key");

        for (i = 0; i < nhelpers; i++) {
                if (helpers[i] == NULL)
                        continue;
                for (j = 0; j < helpers[i]->nkeyblobs; j++) {
                        if (sshbuf_equals(keyblob,
                            helpers[i]->keyblobs[j]) == 0) {
                                sshbuf_free(keyblob);
                                return helpers[i];
                        }
                }
        }
        sshbuf_free(keyblob);
        return NULL;

}

static void
helper_add_key(struct helper *helper, struct sshkey *key)
{
        int r;

        helper->keyblobs = xrecallocarray(helper->keyblobs, helper->nkeyblobs,
            helper->nkeyblobs + 1, sizeof(*helper->keyblobs));
        if ((helper->keyblobs[helper->nkeyblobs] = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new failed");
        if ((r = sshkey_putb(key, helper->keyblobs[helper->nkeyblobs])) != 0)
                fatal_fr(r, "shkey_putb failed");
        helper->nkeyblobs++;
        debug3_f("added %s key for provider %s, now has %zu keys",
            sshkey_type(key), helper->path, helper->nkeyblobs);
}

static void
helper_terminate(struct helper *helper)
{
        size_t i;
        int found = 0;

        if (helper == NULL)
                return;
        if (helper->path == NULL)
                fatal_f("inconsistent helper");

        debug3_f("terminating helper for %s; remaining %zu keys",
            helper->path, helper->nkeyblobs);

        close(helper->fd);
        /* XXX waitpid() */
        helper->fd = -1;
        helper->pid = -1;

        /* repack helpers */
        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--;
        }
        for (i = 0; i < helper->nkeyblobs; i++)
                sshbuf_free(helper->keyblobs[i]);
        free(helper->path);
        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]);
}

int
pkcs11_sign(struct sshkey *key,
    u_char **sigp, size_t *lenp,
    const u_char *data, size_t datalen,
    const char *alg, const char *sk_provider,
    const char *sk_pin, u_int compat)
{
        struct sshbuf *msg = NULL;
        struct helper *helper;
        int status, r;
        u_char *signature = NULL;
        size_t signature_len = 0;
        int ret = SSH_ERR_INTERNAL_ERROR;

        if (sigp != NULL)
                *sigp = NULL;
        if (lenp != NULL)
                *lenp = 0;

        if ((helper = helper_by_key(key)) == NULL || helper->fd == -1)
                fatal_f("no helper for %s key", sshkey_type(key));

        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
            (r = sshkey_puts_plain(key, msg)) != 0 ||
            (r = sshbuf_put_string(msg, data, datalen)) != 0 ||
            (r = sshbuf_put_cstring(msg, alg == NULL ? "" : alg)) != 0 ||
            (r = sshbuf_put_u32(msg, compat)) != 0)
                fatal_fr(r, "compose");
        send_msg(helper->fd, msg);
        sshbuf_reset(msg);

        if ((status = recv_msg(helper->fd, msg)) != SSH2_AGENT_SIGN_RESPONSE) {
                /* XXX translate status to something useful */
                debug_fr(r, "recv_msg");
                ret = SSH_ERR_AGENT_FAILURE;
                goto fail;
        }

        if ((r = sshbuf_get_string(msg, &signature, &signature_len)) != 0)
                fatal_fr(r, "parse");

        /* success */
        if (sigp != NULL) {
                *sigp = signature;
                signature = NULL;
        }
        if (lenp != NULL)
                *lenp = signature_len;
        ret = 0;

 fail:
        free(signature);
        sshbuf_free(msg);
        return ret;
}

/*
 * 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;

        if ((helper = helper_by_key(priv)) == NULL || helper->fd == -1)
                fatal_f("no helper for %s key", sshkey_type(priv));

        debug3_f("private key type %s cert type %s on provider %s",
            sshkey_type(priv), sshkey_type(certpub), helper->path);

        *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 ((r = sshkey_from_private(priv, &ret)) != 0)
                fatal_fr(r, "copy key");

        ret->flags |= SSHKEY_FLAG_EXT;
        if ((r = sshkey_to_certified(ret)) != 0 ||
            (r = sshkey_cert_copy(certpub, ret)) != 0)
                fatal_fr(r, "graft certificate");

        helper_add_key(helper, ret);

        debug3_f("provider %s: %zu remaining keys",
            helper->path, helper->nkeyblobs);

        /* success */
        *certprivp = ret;
        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 ((pid = fork()) == -1) {
                error_f("fork: %s", strerror(errno));
                close(pair[0]);
                close(pair[1]);
                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]);
                closefrom(STDERR_FILENO + 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;
        char *label;
        u_int ret = -1, nkeys, i;
        struct sshbuf *msg;
        struct helper *helper;

        if ((helper = helper_by_provider(name)) == NULL &&
            (helper = pkcs11_start_helper(name)) == NULL)
                return -1;

        debug3_f("add %s", helper->path);

        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);
        debug3_f("response %d", type);
        if (type == SSH2_AGENT_IDENTITIES_ANSWER) {
                if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
                        fatal_fr(r, "parse nkeys");
                debug3_f("helper return %u keys", 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 = sshkey_froms(msg, &k)) != 0 ||
                            (r = sshbuf_get_cstring(msg, &label, NULL)) != 0)
                                fatal_fr(r, "parse key");
                        k->flags |= SSHKEY_FLAG_EXT;
                        helper_add_key(helper, k);
                        (*keysp)[i] = k;
                        if (labelsp)
                                (*labelsp)[i] = label;
                        else
                                free(label);
                }
                /* success */
                ret = 0;
        } else if (type == SSH2_AGENT_FAILURE) {
                if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
                        error_fr(r, "failed to parse failure response");
        }
        if (ret != 0) {
                debug_f("no keys; terminate helper");
                helper_terminate(helper);
        }
        sshbuf_free(msg);
        return ret == 0 ? (int)nkeys : -1;
}

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 ? name : "(null)");
        if ((helper = helper_by_provider(name)) != NULL)
                helper_terminate(helper);
        return 0;
}

void
pkcs11_key_free(struct sshkey *key)
{
        struct helper *helper;
        struct sshbuf *keyblob = NULL;
        size_t i;
        int r, found = 0;

        debug3_f("free %s key", sshkey_type(key));

        if ((helper = helper_by_key(key)) == NULL || helper->fd == -1)
                fatal_f("no helper for %s key", sshkey_type(key));
        if ((keyblob = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new failed");
        if ((r = sshkey_putb(key, keyblob)) != 0)
                fatal_fr(r, "serialise key");

        /* repack keys */
        for (i = 0; i < helper->nkeyblobs; i++) {
                if (sshbuf_equals(keyblob, helper->keyblobs[i]) == 0) {
                        if (found)
                                fatal_f("key recorded more than once");
                        found = 1;
                } else if (found)
                        helper->keyblobs[i - 1] = helper->keyblobs[i];
        }
        if (found) {
                helper->keyblobs = xrecallocarray(helper->keyblobs,
                    helper->nkeyblobs, helper->nkeyblobs - 1,
                    sizeof(*helper->keyblobs));
                helper->nkeyblobs--;
        }
        if (helper->nkeyblobs == 0)
                helper_terminate(helper);
}