/* $OpenBSD: authfd.c,v 1.141 2026/03/05 05:44:15 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Functions for connecting the local authentication agent.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * SSH2 implementation,
 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


#include <sys/types.h>
#include <sys/un.h>
#include <sys/socket.h>

#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <errno.h>

#include "ssh.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "authfd.h"
#include "log.h"
#include "misc.h"
#include "atomicio.h"
#include "ssherr.h"
#include "xmalloc.h"

#define MAX_AGENT_IDENTITIES    2048            /* Max keys in agent reply */
#define MAX_AGENT_REPLY_LEN     (256 * 1024)    /* Max bytes in agent reply */

/* macro to check for "agent failure" message */
#define agent_failed(x) \
    ((x == SSH_AGENT_FAILURE) || \
    (x == SSH_AGENT_EXTENSION_FAILURE) || \
    (x == SSH_COM_AGENT2_FAILURE) || \
    (x == SSH2_AGENT_FAILURE))

/* Convert success/failure response from agent to a err.h status */
static int
decode_reply(u_char type)
{
        if (agent_failed(type))
                return SSH_ERR_AGENT_FAILURE;
        else if (type == SSH_AGENT_SUCCESS)
                return 0;
        else
                return SSH_ERR_INVALID_FORMAT;
}

/*
 * Opens an authentication socket at the provided path and stores the file
 * descriptor in fdp. Returns 0 on success and an error on failure.
 */
int
ssh_get_authentication_socket_path(const char *authsocket, int *fdp)
{
        int sock, oerrno;
        struct sockaddr_un sunaddr;

        debug3_f("path '%s'", authsocket);
        memset(&sunaddr, 0, sizeof(sunaddr));
        sunaddr.sun_family = AF_UNIX;
        strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));

        if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
                return SSH_ERR_SYSTEM_ERROR;

        /* close on exec */
        if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 ||
            connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) == -1) {
                oerrno = errno;
                close(sock);
                errno = oerrno;
                return SSH_ERR_SYSTEM_ERROR;
        }
        if (fdp != NULL)
                *fdp = sock;
        else
                close(sock);
        return 0;
}

/*
 * Opens the default authentication socket and stores the file descriptor in
 * fdp. Returns 0 on success and an error on failure.
 */
int
ssh_get_authentication_socket(int *fdp)
{
        const char *authsocket;

        if (fdp != NULL)
                *fdp = -1;

        authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
        if (authsocket == NULL || *authsocket == '\0')
                return SSH_ERR_AGENT_NOT_PRESENT;

        return ssh_get_authentication_socket_path(authsocket, fdp);
}

/* Communicate with agent: send request and read reply */
static int
ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply)
{
        int r;
        size_t l, len;
        char buf[1024];

        /* Get the length of the message, and format it in the buffer. */
        len = sshbuf_len(request);
        POKE_U32(buf, len);

        /* Send the length and then the packet to the agent. */
        if (atomicio(vwrite, sock, buf, 4) != 4 ||
            atomicio(vwrite, sock, sshbuf_mutable_ptr(request),
            sshbuf_len(request)) != sshbuf_len(request))
                return SSH_ERR_AGENT_COMMUNICATION;
        /*
         * Wait for response from the agent.  First read the length of the
         * response packet.
         */
        if (atomicio(read, sock, buf, 4) != 4)
            return SSH_ERR_AGENT_COMMUNICATION;

        /* Extract the length, and check it for sanity. */
        len = PEEK_U32(buf);
        if (len > MAX_AGENT_REPLY_LEN)
                return SSH_ERR_INVALID_FORMAT;

        /* Read the rest of the response in to the buffer. */
        sshbuf_reset(reply);
        while (len > 0) {
                l = len;
                if (l > sizeof(buf))
                        l = sizeof(buf);
                if (atomicio(read, sock, buf, l) != l)
                        return SSH_ERR_AGENT_COMMUNICATION;
                if ((r = sshbuf_put(reply, buf, l)) != 0)
                        return r;
                len -= l;
        }
        return 0;
}

/* Communicate with agent: sent request, read and decode status reply */
static int
ssh_request_reply_decode(int sock, struct sshbuf *request)
{
        struct sshbuf *reply;
        int r;
        u_char type;

        if ((reply = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = ssh_request_reply(sock, request, reply)) != 0 ||
            (r = sshbuf_get_u8(reply, &type)) != 0 ||
            (r = decode_reply(type)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(reply);
        return r;
}

/*
 * Closes the agent socket if it should be closed (depends on how it was
 * obtained).  The argument must have been returned by
 * ssh_get_authentication_socket().
 */
void
ssh_close_authentication_socket(int sock)
{
        if (getenv(SSH_AUTHSOCKET_ENV_NAME))
                close(sock);
}

/* Lock/unlock agent */
int
ssh_lock_agent(int sock, int lock, const char *password)
{
        int r;
        u_char type = lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK;
        struct sshbuf *msg;

        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_u8(msg, type)) != 0 ||
            (r = sshbuf_put_cstring(msg, password)) != 0 ||
            (r = ssh_request_reply_decode(sock, msg)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(msg);
        return r;
}


static int
deserialise_identity2(struct sshbuf *ids, struct sshkey **keyp, char **commentp)
{
        int r;
        char *comment = NULL;
        const u_char *blob;
        size_t blen;

        if ((r = sshbuf_get_string_direct(ids, &blob, &blen)) != 0 ||
            (r = sshbuf_get_cstring(ids, &comment, NULL)) != 0)
                goto out;
        if ((r = sshkey_from_blob(blob, blen, keyp)) != 0)
                goto out;
        if (commentp != NULL) {
                *commentp = comment;
                comment = NULL;
        }
        r = 0;
 out:
        free(comment);
        return r;
}

/*
 * Fetch list of identities held by the agent.
 */
int
ssh_fetch_identitylist(int sock, struct ssh_identitylist **idlp)
{
        u_char type;
        uint32_t num, i;
        struct sshbuf *msg;
        struct ssh_identitylist *idl = NULL;
        int r;

        /*
         * Send a message to the agent requesting for a list of the
         * identities it can represent.
         */
        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_REQUEST_IDENTITIES)) != 0)
                goto out;

        if ((r = ssh_request_reply(sock, msg, msg)) != 0)
                goto out;

        /* Get message type, and verify that we got a proper answer. */
        if ((r = sshbuf_get_u8(msg, &type)) != 0)
                goto out;
        if (agent_failed(type)) {
                r = SSH_ERR_AGENT_FAILURE;
                goto out;
        } else if (type != SSH2_AGENT_IDENTITIES_ANSWER) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }

        /* Get the number of entries in the response and check it for sanity. */
        if ((r = sshbuf_get_u32(msg, &num)) != 0)
                goto out;
        if (num > MAX_AGENT_IDENTITIES) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        if (num == 0) {
                r = SSH_ERR_AGENT_NO_IDENTITIES;
                goto out;
        }

        /* Deserialise the response into a list of keys/comments */
        if ((idl = calloc(1, sizeof(*idl))) == NULL ||
            (idl->keys = calloc(num, sizeof(*idl->keys))) == NULL ||
            (idl->comments = calloc(num, sizeof(*idl->comments))) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        for (i = 0; i < num;) {
                if ((r = deserialise_identity2(msg, &(idl->keys[i]),
                    &(idl->comments[i]))) != 0) {
                        if (r == SSH_ERR_KEY_TYPE_UNKNOWN) {
                                /* Gracefully skip unknown key types */
                                num--;
                                continue;
                        } else
                                goto out;
                }
                i++;
        }
        idl->nkeys = num;
        *idlp = idl;
        idl = NULL;
        r = 0;
 out:
        sshbuf_free(msg);
        if (idl != NULL)
                ssh_free_identitylist(idl);
        return r;
}

void
ssh_free_identitylist(struct ssh_identitylist *idl)
{
        size_t i;

        if (idl == NULL)
                return;
        for (i = 0; i < idl->nkeys; i++) {
                if (idl->keys != NULL)
                        sshkey_free(idl->keys[i]);
                if (idl->comments != NULL)
                        free(idl->comments[i]);
        }
        free(idl->keys);
        free(idl->comments);
        free(idl);
}

/*
 * Check if the ssh agent has a given key.
 * Returns 0 if found, or a negative SSH_ERR_* error code on failure.
 */
int
ssh_agent_has_key(int sock, const struct sshkey *key)
{
        int r, ret = SSH_ERR_KEY_NOT_FOUND;
        size_t i;
        struct ssh_identitylist *idlist = NULL;

        if ((r = ssh_fetch_identitylist(sock, &idlist)) != 0) {
                return r;
        }

        for (i = 0; i < idlist->nkeys; i++) {
                if (sshkey_equal_public(idlist->keys[i], key)) {
                        ret = 0;
                        break;
                }
        }

        ssh_free_identitylist(idlist);
        return ret;
}

/*
 * Sends a challenge (typically from a server via ssh(1)) to the agent,
 * and waits for a response from the agent.
 * Returns true (non-zero) if the agent gave the correct answer, zero
 * otherwise.
 */


/* encode signature algorithm in flag bits, so we can keep the msg format */
static u_int
agent_encode_alg(const struct sshkey *key, const char *alg)
{
        if (alg != NULL && sshkey_type_plain(key->type) == KEY_RSA) {
                if (strcmp(alg, "rsa-sha2-256") == 0 ||
                    strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0)
                        return SSH_AGENT_RSA_SHA2_256;
                if (strcmp(alg, "rsa-sha2-512") == 0 ||
                    strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0)
                        return SSH_AGENT_RSA_SHA2_512;
        }
        return 0;
}

/* ask agent to sign data, returns err.h code on error, 0 on success */
int
ssh_agent_sign(int sock, const struct sshkey *key,
    u_char **sigp, size_t *lenp,
    const u_char *data, size_t datalen, const char *alg, u_int compat)
{
        struct sshbuf *msg;
        u_char *sig = NULL, type = 0;
        size_t len = 0;
        u_int flags = 0;
        int r = SSH_ERR_INTERNAL_ERROR;

        *sigp = NULL;
        *lenp = 0;

        if (datalen > SSH_KEY_MAX_SIGN_DATA_SIZE)
                return SSH_ERR_INVALID_ARGUMENT;
        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        flags |= agent_encode_alg(key, alg);
        if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
            (r = sshkey_puts(key, msg)) != 0 ||
            (r = sshbuf_put_string(msg, data, datalen)) != 0 ||
            (r = sshbuf_put_u32(msg, flags)) != 0)
                goto out;
        if ((r = ssh_request_reply(sock, msg, msg)) != 0)
                goto out;
        if ((r = sshbuf_get_u8(msg, &type)) != 0)
                goto out;
        if (agent_failed(type)) {
                r = SSH_ERR_AGENT_FAILURE;
                goto out;
        } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        if ((r = sshbuf_get_string(msg, &sig, &len)) != 0)
                goto out;
        /*
         * Check what we actually got back from the agent, in case it returned
         * an incorrect RSA signature algorithm (e.g. "ssh-rsa" (RSA/SHA1) vs.
         * "rsa-sha2-256").
         * We don't do this for FIDO signatures as webauthn vs plain are just
         * different signature formats and not entirely different algorithms.
         */
        if (!sshkey_is_sk(key) &&
            (r = sshkey_check_sigtype(sig, len, alg)) != 0)
                goto out;
        /* success */
        *sigp = sig;
        *lenp = len;
        sig = NULL;
        len = 0;
        r = 0;
 out:
        freezero(sig, len);
        sshbuf_free(msg);
        return r;
}

/* Encode key for a message to the agent. */

static int
encode_dest_constraint_hop(struct sshbuf *m,
    const struct dest_constraint_hop *dch)
{
        struct sshbuf *b;
        u_int i;
        int r;

        if ((b = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_cstring(b, dch->user)) != 0 ||
            (r = sshbuf_put_cstring(b, dch->hostname)) != 0 ||
            (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */
                goto out;
        for (i = 0; i < dch->nkeys; i++) {
                if ((r = sshkey_puts(dch->keys[i], b)) != 0 ||
                    (r = sshbuf_put_u8(b, dch->key_is_ca[i] != 0)) != 0)
                        goto out;
        }
        if ((r = sshbuf_put_stringb(m, b)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(b);
        return r;
}

static int
encode_dest_constraint(struct sshbuf *m, const struct dest_constraint *dc)
{
        struct sshbuf *b;
        int r;

        if ((b = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = encode_dest_constraint_hop(b, &dc->from)) != 0 ||
            (r = encode_dest_constraint_hop(b, &dc->to)) != 0 ||
            (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */
                goto out;
        if ((r = sshbuf_put_stringb(m, b)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(b);
        return r;
}

static int
encode_constraints(struct sshbuf *m, u_int life, u_int confirm,
    const char *provider,
    struct dest_constraint **dest_constraints, size_t ndest_constraints,
    int cert_only, struct sshkey **certs, size_t ncerts)
{
        int r;
        struct sshbuf *b = NULL;
        size_t i;

        if (life != 0) {
                if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_LIFETIME)) != 0 ||
                    (r = sshbuf_put_u32(m, life)) != 0)
                        goto out;
        }
        if (confirm != 0) {
                if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_CONFIRM)) != 0)
                        goto out;
        }
        if (provider != NULL) {
                if ((r = sshbuf_put_u8(m,
                    SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 ||
                    (r = sshbuf_put_cstring(m,
                    "sk-provider@openssh.com")) != 0 ||
                    (r = sshbuf_put_cstring(m, provider)) != 0)
                        goto out;
        }
        if (dest_constraints != NULL && ndest_constraints > 0) {
                if ((b = sshbuf_new()) == NULL) {
                        r = SSH_ERR_ALLOC_FAIL;
                        goto out;
                }
                for (i = 0; i < ndest_constraints; i++) {
                        if ((r = encode_dest_constraint(b,
                            dest_constraints[i])) != 0)
                                goto out;
                }
                if ((r = sshbuf_put_u8(m,
                    SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 ||
                    (r = sshbuf_put_cstring(m,
                    "restrict-destination-v00@openssh.com")) != 0 ||
                    (r = sshbuf_put_stringb(m, b)) != 0)
                        goto out;
                sshbuf_free(b);
                b = NULL;
        }
        if (ncerts != 0) {
                if ((b = sshbuf_new()) == NULL) {
                        r = SSH_ERR_ALLOC_FAIL;
                        goto out;
                }
                for (i = 0; i < ncerts; i++) {
                        if ((r = sshkey_puts(certs[i], b)) != 0)
                                goto out;
                }
                if ((r = sshbuf_put_u8(m,
                    SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 ||
                    (r = sshbuf_put_cstring(m,
                    "associated-certs-v00@openssh.com")) != 0 ||
                    (r = sshbuf_put_u8(m, cert_only != 0)) != 0 ||
                    (r = sshbuf_put_stringb(m, b)) != 0)
                        goto out;
                sshbuf_free(b);
                b = NULL;
        }
        r = 0;
 out:
        sshbuf_free(b);
        return r;
}

/*
 * Adds an identity to the authentication server.
 * This call is intended only for use by ssh-add(1) and like applications.
 */
int
ssh_add_identity_constrained(int sock, struct sshkey *key,
    const char *comment, u_int life, u_int confirm,
    const char *provider, struct dest_constraint **dest_constraints,
    size_t ndest_constraints)
{
        struct sshbuf *msg;
        int r, constrained = (life || confirm || provider || dest_constraints);
        u_char type;

        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;

        switch (key->type) {
#ifdef WITH_OPENSSL
        case KEY_RSA:
        case KEY_RSA_CERT:
        case KEY_ECDSA:
        case KEY_ECDSA_CERT:
        case KEY_ECDSA_SK:
        case KEY_ECDSA_SK_CERT:
#endif
        case KEY_ED25519:
        case KEY_ED25519_CERT:
        case KEY_ED25519_SK:
        case KEY_ED25519_SK_CERT:
                type = constrained ?
                    SSH2_AGENTC_ADD_ID_CONSTRAINED :
                    SSH2_AGENTC_ADD_IDENTITY;
                if ((r = sshbuf_put_u8(msg, type)) != 0 ||
                    (r = sshkey_private_serialize(key, msg)) != 0 ||
                    (r = sshbuf_put_cstring(msg, comment)) != 0)
                        goto out;
                break;
        default:
                r = SSH_ERR_INVALID_ARGUMENT;
                goto out;
        }
        if (constrained &&
            (r = encode_constraints(msg, life, confirm, provider,
            dest_constraints, ndest_constraints, 0, NULL, 0)) != 0)
                goto out;
        if ((r = ssh_request_reply_decode(sock, msg)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(msg);
        return r;
}

/*
 * Removes an identity from the authentication server.
 * This call is intended only for use by ssh-add(1) and like applications.
 */
int
ssh_remove_identity(int sock, const struct sshkey *key)
{
        struct sshbuf *msg;
        int r;
        u_char *blob = NULL;
        size_t blen;

        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;

        if (key->type != KEY_UNSPEC) {
                if ((r = sshkey_to_blob(key, &blob, &blen)) != 0)
                        goto out;
                if ((r = sshbuf_put_u8(msg,
                    SSH2_AGENTC_REMOVE_IDENTITY)) != 0 ||
                    (r = sshbuf_put_string(msg, blob, blen)) != 0)
                        goto out;
        } else {
                r = SSH_ERR_INVALID_ARGUMENT;
                goto out;
        }
        if ((r = ssh_request_reply_decode(sock, msg)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        if (blob != NULL)
                freezero(blob, blen);
        sshbuf_free(msg);
        return r;
}

/*
 * Add/remove an token-based identity from the authentication server.
 * This call is intended only for use by ssh-add(1) and like applications.
 */
int
ssh_update_card(int sock, int add, const char *reader_id, const char *pin,
    u_int life, u_int confirm,
    struct dest_constraint **dest_constraints, size_t ndest_constraints,
    int cert_only, struct sshkey **certs, size_t ncerts)
{
        struct sshbuf *msg;
        int r, constrained = (life || confirm || dest_constraints || certs);
        u_char type;

        if (add) {
                type = constrained ?
                    SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
                    SSH_AGENTC_ADD_SMARTCARD_KEY;
        } else
                type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;

        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_u8(msg, type)) != 0 ||
            (r = sshbuf_put_cstring(msg, reader_id)) != 0 ||
            (r = sshbuf_put_cstring(msg, pin)) != 0)
                goto out;
        if (constrained &&
            (r = encode_constraints(msg, life, confirm, NULL,
            dest_constraints, ndest_constraints,
            cert_only, certs, ncerts)) != 0)
                goto out;
        if ((r = ssh_request_reply_decode(sock, msg)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(msg);
        return r;
}

/*
 * Removes all identities from the agent.
 * This call is intended only for use by ssh-add(1) and like applications.
 *
 * This supports the SSH protocol 1 message to because, when clearing all
 * keys from an agent, we generally want to clear both protocol v1 and v2
 * keys.
 */
int
ssh_remove_all_identities(int sock, int version)
{
        struct sshbuf *msg;
        u_char type = (version == 1) ?
            SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
            SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
        int r;

        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_u8(msg, type)) != 0)
                goto out;
        if ((r = ssh_request_reply_decode(sock, msg)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(msg);
        return r;
}

/* Binds a session ID to a hostkey via the initial KEX signature. */
int
ssh_agent_bind_hostkey(int sock, const struct sshkey *key,
    const struct sshbuf *session_id, const struct sshbuf *signature,
    int forwarding)
{
        struct sshbuf *msg;
        int r;

        if (key == NULL || session_id == NULL || signature == NULL)
                return SSH_ERR_INVALID_ARGUMENT;
        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_u8(msg, SSH_AGENTC_EXTENSION)) != 0 ||
            (r = sshbuf_put_cstring(msg, "session-bind@openssh.com")) != 0 ||
            (r = sshkey_puts(key, msg)) != 0 ||
            (r = sshbuf_put_stringb(msg, session_id)) != 0 ||
            (r = sshbuf_put_stringb(msg, signature)) != 0 ||
            (r = sshbuf_put_u8(msg, forwarding ? 1 : 0)) != 0)
                goto out;
        if ((r = ssh_request_reply_decode(sock, msg)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(msg);
        return r;
}

/* Queries supported extension request types */
int
ssh_agent_query_extensions(int sock, char ***exts)
{
        struct sshbuf *msg;
        int r;
        u_char type;
        char *cp = NULL, **ret = NULL;
        size_t i = 0;

        *exts = NULL;
        if ((msg = sshbuf_new()) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_put_u8(msg, SSH_AGENTC_EXTENSION)) != 0 ||
            (r = sshbuf_put_cstring(msg, "query")) != 0)
                goto out;
        if ((r = ssh_request_reply(sock, msg, msg)) != 0)
                goto out;
        if ((r = sshbuf_get_u8(msg, &type)) != 0)
                goto out;
        if (agent_failed(type)) {
                r = SSH_ERR_AGENT_FAILURE;
                goto out;
        }
        /* Reply should start with "query" */
        if (type != SSH_AGENT_EXTENSION_RESPONSE ||
           (r = sshbuf_get_cstring(msg, &cp, NULL)) != 0 ||
           strcmp(cp, "query") != 0) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        ret = calloc(1, sizeof(*ret));
        while (sshbuf_len(msg)) {
                ret = xrecallocarray(ret, i + 1, i + 2, sizeof(*ret));
                if ((r = sshbuf_get_cstring(msg, ret + i, NULL)) != 0) {
                        r = SSH_ERR_INVALID_FORMAT;
                        goto out;
                }
                i++;
        }
        /* success */
        r = 0;
        *exts = ret;
        ret = NULL; /* transferred */
 out:
        free(cp);
        stringlist_free(ret);
        sshbuf_free(msg);
        return r;
}