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[openssh-git.git] / sshconnect2.c

/*
 * 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 "includes.h"
RCSID("$OpenBSD: sshconnect2.c,v 1.141 2005/07/25 11:59:40 markus Exp $");

#include "openbsd-compat/sys-queue.h"

#include "ssh.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "buffer.h"
#include "packet.h"
#include "compat.h"
#include "bufaux.h"
#include "cipher.h"
#include "kex.h"
#include "myproposal.h"
#include "sshconnect.h"
#include "authfile.h"
#include "dh.h"
#include "authfd.h"
#include "log.h"
#include "readconf.h"
#include "misc.h"
#include "match.h"
#include "dispatch.h"
#include "canohost.h"
#include "msg.h"
#include "pathnames.h"

#ifdef GSSAPI
#include "ssh-gss.h"
#endif

/* import */
extern char *client_version_string;
extern char *server_version_string;
extern Options options;

/*
 * SSH2 key exchange
 */

u_char *session_id2 = NULL;
u_int session_id2_len = 0;

char *xxx_host;
struct sockaddr *xxx_hostaddr;

Kex *xxx_kex = NULL;

static int
verify_host_key_callback(Key *hostkey)
{
        if (verify_host_key(xxx_host, xxx_hostaddr, hostkey) == -1)
                fatal("Host key verification failed.");
        return 0;
}

void
ssh_kex2(char *host, struct sockaddr *hostaddr)
{
        Kex *kex;

        xxx_host = host;
        xxx_hostaddr = hostaddr;

        if (options.ciphers == (char *)-1) {
                logit("No valid ciphers for protocol version 2 given, using defaults.");
                options.ciphers = NULL;
        }
        if (options.ciphers != NULL) {
                myproposal[PROPOSAL_ENC_ALGS_CTOS] =
                myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
        }
        myproposal[PROPOSAL_ENC_ALGS_CTOS] =
            compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
        myproposal[PROPOSAL_ENC_ALGS_STOC] =
            compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
        if (options.compression) {
                myproposal[PROPOSAL_COMP_ALGS_CTOS] =
                myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib@openssh.com,zlib,none";
        } else {
                myproposal[PROPOSAL_COMP_ALGS_CTOS] =
                myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com,zlib";
        }
        if (options.macs != NULL) {
                myproposal[PROPOSAL_MAC_ALGS_CTOS] =
                myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
        }
        if (options.hostkeyalgorithms != NULL)
                myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
                    options.hostkeyalgorithms;

        if (options.rekey_limit)
                packet_set_rekey_limit(options.rekey_limit);

        /* start key exchange */
        kex = kex_setup(myproposal);
        kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
        kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
        kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
        kex->client_version_string=client_version_string;
        kex->server_version_string=server_version_string;
        kex->verify_host_key=&verify_host_key_callback;

        xxx_kex = kex;

        dispatch_run(DISPATCH_BLOCK, &kex->done, kex);

        session_id2 = kex->session_id;
        session_id2_len = kex->session_id_len;

#ifdef DEBUG_KEXDH
        /* send 1st encrypted/maced/compressed message */
        packet_start(SSH2_MSG_IGNORE);
        packet_put_cstring("markus");
        packet_send();
        packet_write_wait();
#endif
}

/*
 * Authenticate user
 */

typedef struct Authctxt Authctxt;
typedef struct Authmethod Authmethod;
typedef struct identity Identity;
typedef struct idlist Idlist;

struct identity {
        TAILQ_ENTRY(identity) next;
        AuthenticationConnection *ac;   /* set if agent supports key */
        Key     *key;                   /* public/private key */
        char    *filename;              /* comment for agent-only keys */
        int     tried;
        int     isprivate;              /* key points to the private key */
};
TAILQ_HEAD(idlist, identity);

struct Authctxt {
        const char *server_user;
        const char *local_user;
        const char *host;
        const char *service;
        Authmethod *method;
        int success;
        char *authlist;
        /* pubkey */
        Idlist keys;
        AuthenticationConnection *agent;
        /* hostbased */
        Sensitive *sensitive;
        /* kbd-interactive */
        int info_req_seen;
        /* generic */
        void *methoddata;
};
struct Authmethod {
        char    *name;          /* string to compare against server's list */
        int     (*userauth)(Authctxt *authctxt);
        int     *enabled;       /* flag in option struct that enables method */
        int     *batch_flag;    /* flag in option struct that disables method */
};

void    input_userauth_success(int, u_int32_t, void *);
void    input_userauth_failure(int, u_int32_t, void *);
void    input_userauth_banner(int, u_int32_t, void *);
void    input_userauth_error(int, u_int32_t, void *);
void    input_userauth_info_req(int, u_int32_t, void *);
void    input_userauth_pk_ok(int, u_int32_t, void *);
void    input_userauth_passwd_changereq(int, u_int32_t, void *);

int     userauth_none(Authctxt *);
int     userauth_pubkey(Authctxt *);
int     userauth_passwd(Authctxt *);
int     userauth_kbdint(Authctxt *);
int     userauth_hostbased(Authctxt *);
int     userauth_kerberos(Authctxt *);

#ifdef GSSAPI
int     userauth_gssapi(Authctxt *authctxt);
void    input_gssapi_response(int type, u_int32_t, void *);
void    input_gssapi_token(int type, u_int32_t, void *);
void    input_gssapi_hash(int type, u_int32_t, void *);
void    input_gssapi_error(int, u_int32_t, void *);
void    input_gssapi_errtok(int, u_int32_t, void *);
#endif

void    userauth(Authctxt *, char *);

static int sign_and_send_pubkey(Authctxt *, Identity *);
static void pubkey_prepare(Authctxt *);
static void pubkey_cleanup(Authctxt *);
static Key *load_identity_file(char *);

static Authmethod *authmethod_get(char *authlist);
static Authmethod *authmethod_lookup(const char *name);
static char *authmethods_get(void);

Authmethod authmethods[] = {
#ifdef GSSAPI
        {"gssapi-with-mic",
                userauth_gssapi,
                &options.gss_authentication,
                NULL},
#endif
        {"hostbased",
                userauth_hostbased,
                &options.hostbased_authentication,
                NULL},
        {"publickey",
                userauth_pubkey,
                &options.pubkey_authentication,
                NULL},
        {"keyboard-interactive",
                userauth_kbdint,
                &options.kbd_interactive_authentication,
                &options.batch_mode},
        {"password",
                userauth_passwd,
                &options.password_authentication,
                &options.batch_mode},
        {"none",
                userauth_none,
                NULL,
                NULL},
        {NULL, NULL, NULL, NULL}
};

void
ssh_userauth2(const char *local_user, const char *server_user, char *host,
    Sensitive *sensitive)
{
        Authctxt authctxt;
        int type;

        if (options.challenge_response_authentication)
                options.kbd_interactive_authentication = 1;

        packet_start(SSH2_MSG_SERVICE_REQUEST);
        packet_put_cstring("ssh-userauth");
        packet_send();
        debug("SSH2_MSG_SERVICE_REQUEST sent");
        packet_write_wait();
        type = packet_read();
        if (type != SSH2_MSG_SERVICE_ACCEPT)
                fatal("Server denied authentication request: %d", type);
        if (packet_remaining() > 0) {
                char *reply = packet_get_string(NULL);
                debug2("service_accept: %s", reply);
                xfree(reply);
        } else {
                debug2("buggy server: service_accept w/o service");
        }
        packet_check_eom();
        debug("SSH2_MSG_SERVICE_ACCEPT received");

        if (options.preferred_authentications == NULL)
                options.preferred_authentications = authmethods_get();

        /* setup authentication context */
        memset(&authctxt, 0, sizeof(authctxt));
        pubkey_prepare(&authctxt);
        authctxt.server_user = server_user;
        authctxt.local_user = local_user;
        authctxt.host = host;
        authctxt.service = "ssh-connection";            /* service name */
        authctxt.success = 0;
        authctxt.method = authmethod_lookup("none");
        authctxt.authlist = NULL;
        authctxt.methoddata = NULL;
        authctxt.sensitive = sensitive;
        authctxt.info_req_seen = 0;
        if (authctxt.method == NULL)
                fatal("ssh_userauth2: internal error: cannot send userauth none request");

        /* initial userauth request */
        userauth_none(&authctxt);

        dispatch_init(&input_userauth_error);
        dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
        dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
        dispatch_set(SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
        dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt);     /* loop until success */

        pubkey_cleanup(&authctxt);
        dispatch_range(SSH2_MSG_USERAUTH_MIN, SSH2_MSG_USERAUTH_MAX, NULL);

        debug("Authentication succeeded (%s).", authctxt.method->name);
}

void
userauth(Authctxt *authctxt, char *authlist)
{
        if (authctxt->methoddata) {
                xfree(authctxt->methoddata);
                authctxt->methoddata = NULL;
        }
        if (authlist == NULL) {
                authlist = authctxt->authlist;
        } else {
                if (authctxt->authlist)
                        xfree(authctxt->authlist);
                authctxt->authlist = authlist;
        }
        for (;;) {
                Authmethod *method = authmethod_get(authlist);
                if (method == NULL)
                        fatal("Permission denied (%s).", authlist);
                authctxt->method = method;

                /* reset the per method handler */
                dispatch_range(SSH2_MSG_USERAUTH_PER_METHOD_MIN,
                    SSH2_MSG_USERAUTH_PER_METHOD_MAX, NULL);

                /* and try new method */
                if (method->userauth(authctxt) != 0) {
                        debug2("we sent a %s packet, wait for reply", method->name);
                        break;
                } else {
                        debug2("we did not send a packet, disable method");
                        method->enabled = NULL;
                }
        }
}

void
input_userauth_error(int type, u_int32_t seq, void *ctxt)
{
        fatal("input_userauth_error: bad message during authentication: "
            "type %d", type);
}

void
input_userauth_banner(int type, u_int32_t seq, void *ctxt)
{
        char *msg, *lang;

        debug3("input_userauth_banner");
        msg = packet_get_string(NULL);
        lang = packet_get_string(NULL);
        if (options.log_level > SYSLOG_LEVEL_QUIET)
                fprintf(stderr, "%s", msg);
        xfree(msg);
        xfree(lang);
}

void
input_userauth_success(int type, u_int32_t seq, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        if (authctxt == NULL)
                fatal("input_userauth_success: no authentication context");
        if (authctxt->authlist) {
                xfree(authctxt->authlist);
                authctxt->authlist = NULL;
        }
        if (authctxt->methoddata) {
                xfree(authctxt->methoddata);
                authctxt->methoddata = NULL;
        }
        authctxt->success = 1;                  /* break out */
}

void
input_userauth_failure(int type, u_int32_t seq, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        char *authlist = NULL;
        int partial;

        if (authctxt == NULL)
                fatal("input_userauth_failure: no authentication context");

        authlist = packet_get_string(NULL);
        partial = packet_get_char();
        packet_check_eom();

        if (partial != 0)
                logit("Authenticated with partial success.");
        debug("Authentications that can continue: %s", authlist);

        userauth(authctxt, authlist);
}
void
input_userauth_pk_ok(int type, u_int32_t seq, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        Key *key = NULL;
        Identity *id = NULL;
        Buffer b;
        int pktype, sent = 0;
        u_int alen, blen;
        char *pkalg, *fp;
        u_char *pkblob;

        if (authctxt == NULL)
                fatal("input_userauth_pk_ok: no authentication context");
        if (datafellows & SSH_BUG_PKOK) {
                /* this is similar to SSH_BUG_PKAUTH */
                debug2("input_userauth_pk_ok: SSH_BUG_PKOK");
                pkblob = packet_get_string(&blen);
                buffer_init(&b);
                buffer_append(&b, pkblob, blen);
                pkalg = buffer_get_string(&b, &alen);
                buffer_free(&b);
        } else {
                pkalg = packet_get_string(&alen);
                pkblob = packet_get_string(&blen);
        }
        packet_check_eom();

        debug("Server accepts key: pkalg %s blen %u", pkalg, blen);

        if ((pktype = key_type_from_name(pkalg)) == KEY_UNSPEC) {
                debug("unknown pkalg %s", pkalg);
                goto done;
        }
        if ((key = key_from_blob(pkblob, blen)) == NULL) {
                debug("no key from blob. pkalg %s", pkalg);
                goto done;
        }
        if (key->type != pktype) {
                error("input_userauth_pk_ok: type mismatch "
                    "for decoded key (received %d, expected %d)",
                    key->type, pktype);
                goto done;
        }
        fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
        debug2("input_userauth_pk_ok: fp %s", fp);
        xfree(fp);

        /*
         * search keys in the reverse order, because last candidate has been
         * moved to the end of the queue.  this also avoids confusion by
         * duplicate keys
         */
        TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
                if (key_equal(key, id->key)) {
                        sent = sign_and_send_pubkey(authctxt, id);
                        break;
                }
        }
done:
        if (key != NULL)
                key_free(key);
        xfree(pkalg);
        xfree(pkblob);

        /* try another method if we did not send a packet */
        if (sent == 0)
                userauth(authctxt, NULL);
}

#ifdef GSSAPI
int
userauth_gssapi(Authctxt *authctxt)
{
        Gssctxt *gssctxt = NULL;
        static gss_OID_set gss_supported = NULL;
        static u_int mech = 0;
        OM_uint32 min;
        int ok = 0;

        /* Try one GSSAPI method at a time, rather than sending them all at
         * once. */

        if (gss_supported == NULL)
                gss_indicate_mechs(&min, &gss_supported);

        /* Check to see if the mechanism is usable before we offer it */
        while (mech < gss_supported->count && !ok) {
                if (gssctxt)
                        ssh_gssapi_delete_ctx(&gssctxt);
                ssh_gssapi_build_ctx(&gssctxt);
                ssh_gssapi_set_oid(gssctxt, &gss_supported->elements[mech]);

                /* My DER encoding requires length<128 */
                if (gss_supported->elements[mech].length < 128 &&
                    !GSS_ERROR(ssh_gssapi_import_name(gssctxt,
                    authctxt->host))) {
                        ok = 1; /* Mechanism works */
                } else {
                        mech++;
                }
        }

        if (!ok)
                return 0;

        authctxt->methoddata=(void *)gssctxt;

        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_cstring(authctxt->server_user);
        packet_put_cstring(authctxt->service);
        packet_put_cstring(authctxt->method->name);

        packet_put_int(1);

        packet_put_int((gss_supported->elements[mech].length) + 2);
        packet_put_char(SSH_GSS_OIDTYPE);
        packet_put_char(gss_supported->elements[mech].length);
        packet_put_raw(gss_supported->elements[mech].elements,
            gss_supported->elements[mech].length);

        packet_send();

        dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
        dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
        dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
        dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);

        mech++; /* Move along to next candidate */

        return 1;
}

static OM_uint32
process_gssapi_token(void *ctxt, gss_buffer_t recv_tok)
{
        Authctxt *authctxt = ctxt;
        Gssctxt *gssctxt = authctxt->methoddata;
        gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
        gss_buffer_desc gssbuf, mic;
        OM_uint32 status, ms, flags;
        Buffer b;

        status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
            recv_tok, &send_tok, &flags);

        if (send_tok.length > 0) {
                if (GSS_ERROR(status))
                        packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
                else
                        packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);

                packet_put_string(send_tok.value, send_tok.length);
                packet_send();
                gss_release_buffer(&ms, &send_tok);
        }

        if (status == GSS_S_COMPLETE) {
                /* send either complete or MIC, depending on mechanism */
                if (!(flags & GSS_C_INTEG_FLAG)) {
                        packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
                        packet_send();
                } else {
                        ssh_gssapi_buildmic(&b, authctxt->server_user,
                            authctxt->service, "gssapi-with-mic");

                        gssbuf.value = buffer_ptr(&b);
                        gssbuf.length = buffer_len(&b);

                        status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);

                        if (!GSS_ERROR(status)) {
                                packet_start(SSH2_MSG_USERAUTH_GSSAPI_MIC);
                                packet_put_string(mic.value, mic.length);

                                packet_send();
                        }

                        buffer_free(&b);
                        gss_release_buffer(&ms, &mic);
                }
        }

        return status;
}

void
input_gssapi_response(int type, u_int32_t plen, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        Gssctxt *gssctxt;
        int oidlen;
        char *oidv;

        if (authctxt == NULL)
                fatal("input_gssapi_response: no authentication context");
        gssctxt = authctxt->methoddata;

        /* Setup our OID */
        oidv = packet_get_string(&oidlen);

        if (oidlen <= 2 ||
            oidv[0] != SSH_GSS_OIDTYPE ||
            oidv[1] != oidlen - 2) {
                xfree(oidv);
                debug("Badly encoded mechanism OID received");
                userauth(authctxt, NULL);
                return;
        }

        if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
                fatal("Server returned different OID than expected");

        packet_check_eom();

        xfree(oidv);

        if (GSS_ERROR(process_gssapi_token(ctxt, GSS_C_NO_BUFFER))) {
                /* Start again with next method on list */
                debug("Trying to start again");
                userauth(authctxt, NULL);
                return;
        }
}

void
input_gssapi_token(int type, u_int32_t plen, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        gss_buffer_desc recv_tok;
        OM_uint32 status;
        u_int slen;

        if (authctxt == NULL)
                fatal("input_gssapi_response: no authentication context");

        recv_tok.value = packet_get_string(&slen);
        recv_tok.length = slen; /* safe typecast */

        packet_check_eom();

        status = process_gssapi_token(ctxt, &recv_tok);

        xfree(recv_tok.value);

        if (GSS_ERROR(status)) {
                /* Start again with the next method in the list */
                userauth(authctxt, NULL);
                return;
        }
}

void
input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        Gssctxt *gssctxt;
        gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
        gss_buffer_desc recv_tok;
        OM_uint32 status, ms;
        u_int len;

        if (authctxt == NULL)
                fatal("input_gssapi_response: no authentication context");
        gssctxt = authctxt->methoddata;

        recv_tok.value = packet_get_string(&len);
        recv_tok.length = len;

        packet_check_eom();

        /* Stick it into GSSAPI and see what it says */
        status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
            &recv_tok, &send_tok, NULL);

        xfree(recv_tok.value);
        gss_release_buffer(&ms, &send_tok);

        /* Server will be returning a failed packet after this one */
}

void
input_gssapi_error(int type, u_int32_t plen, void *ctxt)
{
        OM_uint32 maj, min;
        char *msg;
        char *lang;

        maj=packet_get_int();
        min=packet_get_int();
        msg=packet_get_string(NULL);
        lang=packet_get_string(NULL);

        packet_check_eom();

        debug("Server GSSAPI Error:\n%s\n", msg);
        xfree(msg);
        xfree(lang);
}
#endif /* GSSAPI */

int
userauth_none(Authctxt *authctxt)
{
        /* initial userauth request */
        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_cstring(authctxt->server_user);
        packet_put_cstring(authctxt->service);
        packet_put_cstring(authctxt->method->name);
        packet_send();
        return 1;
}

int
userauth_passwd(Authctxt *authctxt)
{
        static int attempt = 0;
        char prompt[150];
        char *password;

        if (attempt++ >= options.number_of_password_prompts)
                return 0;

        if (attempt != 1)
                error("Permission denied, please try again.");

        snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
            authctxt->server_user, authctxt->host);
        password = read_passphrase(prompt, 0);
        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_cstring(authctxt->server_user);
        packet_put_cstring(authctxt->service);
        packet_put_cstring(authctxt->method->name);
        packet_put_char(0);
        packet_put_cstring(password);
        memset(password, 0, strlen(password));
        xfree(password);
        packet_add_padding(64);
        packet_send();

        dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
            &input_userauth_passwd_changereq);

        return 1;
}
/*
 * parse PASSWD_CHANGEREQ, prompt user and send SSH2_MSG_USERAUTH_REQUEST
 */
void
input_userauth_passwd_changereq(int type, u_int32_t seqnr, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        char *info, *lang, *password = NULL, *retype = NULL;
        char prompt[150];

        debug2("input_userauth_passwd_changereq");

        if (authctxt == NULL)
                fatal("input_userauth_passwd_changereq: "
                    "no authentication context");

        info = packet_get_string(NULL);
        lang = packet_get_string(NULL);
        if (strlen(info) > 0)
                logit("%s", info);
        xfree(info);
        xfree(lang);
        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_cstring(authctxt->server_user);
        packet_put_cstring(authctxt->service);
        packet_put_cstring(authctxt->method->name);
        packet_put_char(1);                     /* additional info */
        snprintf(prompt, sizeof(prompt),
            "Enter %.30s@%.128s's old password: ",
            authctxt->server_user, authctxt->host);
        password = read_passphrase(prompt, 0);
        packet_put_cstring(password);
        memset(password, 0, strlen(password));
        xfree(password);
        password = NULL;
        while (password == NULL) {
                snprintf(prompt, sizeof(prompt),
                    "Enter %.30s@%.128s's new password: ",
                    authctxt->server_user, authctxt->host);
                password = read_passphrase(prompt, RP_ALLOW_EOF);
                if (password == NULL) {
                        /* bail out */
                        return;
                }
                snprintf(prompt, sizeof(prompt),
                    "Retype %.30s@%.128s's new password: ",
                    authctxt->server_user, authctxt->host);
                retype = read_passphrase(prompt, 0);
                if (strcmp(password, retype) != 0) {
                        memset(password, 0, strlen(password));
                        xfree(password);
                        logit("Mismatch; try again, EOF to quit.");
                        password = NULL;
                }
                memset(retype, 0, strlen(retype));
                xfree(retype);
        }
        packet_put_cstring(password);
        memset(password, 0, strlen(password));
        xfree(password);
        packet_add_padding(64);
        packet_send();

        dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
            &input_userauth_passwd_changereq);
}

static int
identity_sign(Identity *id, u_char **sigp, u_int *lenp,
    u_char *data, u_int datalen)
{
        Key *prv;
        int ret;

        /* the agent supports this key */
        if (id->ac)
                return (ssh_agent_sign(id->ac, id->key, sigp, lenp,
                    data, datalen));
        /*
         * we have already loaded the private key or
         * the private key is stored in external hardware
         */
        if (id->isprivate || (id->key->flags & KEY_FLAG_EXT))
                return (key_sign(id->key, sigp, lenp, data, datalen));
        /* load the private key from the file */
        if ((prv = load_identity_file(id->filename)) == NULL)
                return (-1);
        ret = key_sign(prv, sigp, lenp, data, datalen);
        key_free(prv);
        return (ret);
}

static int
sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
{
        Buffer b;
        u_char *blob, *signature;
        u_int bloblen, slen;
        u_int skip = 0;
        int ret = -1;
        int have_sig = 1;

        debug3("sign_and_send_pubkey");

        if (key_to_blob(id->key, &blob, &bloblen) == 0) {
                /* we cannot handle this key */
                debug3("sign_and_send_pubkey: cannot handle key");
                return 0;
        }
        /* data to be signed */
        buffer_init(&b);
        if (datafellows & SSH_OLD_SESSIONID) {
                buffer_append(&b, session_id2, session_id2_len);
                skip = session_id2_len;
        } else {
                buffer_put_string(&b, session_id2, session_id2_len);
                skip = buffer_len(&b);
        }
        buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
        buffer_put_cstring(&b, authctxt->server_user);
        buffer_put_cstring(&b,
            datafellows & SSH_BUG_PKSERVICE ?
            "ssh-userauth" :
            authctxt->service);
        if (datafellows & SSH_BUG_PKAUTH) {
                buffer_put_char(&b, have_sig);
        } else {
                buffer_put_cstring(&b, authctxt->method->name);
                buffer_put_char(&b, have_sig);
                buffer_put_cstring(&b, key_ssh_name(id->key));
        }
        buffer_put_string(&b, blob, bloblen);

        /* generate signature */
        ret = identity_sign(id, &signature, &slen,
            buffer_ptr(&b), buffer_len(&b));
        if (ret == -1) {
                xfree(blob);
                buffer_free(&b);
                return 0;
        }
#ifdef DEBUG_PK
        buffer_dump(&b);
#endif
        if (datafellows & SSH_BUG_PKSERVICE) {
                buffer_clear(&b);
                buffer_append(&b, session_id2, session_id2_len);
                skip = session_id2_len;
                buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
                buffer_put_cstring(&b, authctxt->server_user);
                buffer_put_cstring(&b, authctxt->service);
                buffer_put_cstring(&b, authctxt->method->name);
                buffer_put_char(&b, have_sig);
                if (!(datafellows & SSH_BUG_PKAUTH))
                        buffer_put_cstring(&b, key_ssh_name(id->key));
                buffer_put_string(&b, blob, bloblen);
        }
        xfree(blob);

        /* append signature */
        buffer_put_string(&b, signature, slen);
        xfree(signature);

        /* skip session id and packet type */
        if (buffer_len(&b) < skip + 1)
                fatal("userauth_pubkey: internal error");
        buffer_consume(&b, skip + 1);

        /* put remaining data from buffer into packet */
        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_raw(buffer_ptr(&b), buffer_len(&b));
        buffer_free(&b);
        packet_send();

        return 1;
}

static int
send_pubkey_test(Authctxt *authctxt, Identity *id)
{
        u_char *blob;
        u_int bloblen, have_sig = 0;

        debug3("send_pubkey_test");

        if (key_to_blob(id->key, &blob, &bloblen) == 0) {
                /* we cannot handle this key */
                debug3("send_pubkey_test: cannot handle key");
                return 0;
        }
        /* register callback for USERAUTH_PK_OK message */
        dispatch_set(SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);

        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_cstring(authctxt->server_user);
        packet_put_cstring(authctxt->service);
        packet_put_cstring(authctxt->method->name);
        packet_put_char(have_sig);
        if (!(datafellows & SSH_BUG_PKAUTH))
                packet_put_cstring(key_ssh_name(id->key));
        packet_put_string(blob, bloblen);
        xfree(blob);
        packet_send();
        return 1;
}

static Key *
load_identity_file(char *filename)
{
        Key *private;
        char prompt[300], *passphrase;
        int quit, i;
        struct stat st;

        if (stat(filename, &st) < 0) {
                debug3("no such identity: %s", filename);
                return NULL;
        }
        private = key_load_private_type(KEY_UNSPEC, filename, "", NULL);
        if (private == NULL) {
                if (options.batch_mode)
                        return NULL;
                snprintf(prompt, sizeof prompt,
                    "Enter passphrase for key '%.100s': ", filename);
                for (i = 0; i < options.number_of_password_prompts; i++) {
                        passphrase = read_passphrase(prompt, 0);
                        if (strcmp(passphrase, "") != 0) {
                                private = key_load_private_type(KEY_UNSPEC, filename,
                                    passphrase, NULL);
                                quit = 0;
                        } else {
                                debug2("no passphrase given, try next key");
                                quit = 1;
                        }
                        memset(passphrase, 0, strlen(passphrase));
                        xfree(passphrase);
                        if (private != NULL || quit)
                                break;
                        debug2("bad passphrase given, try again...");
                }
        }
        return private;
}

/*
 * try keys in the following order:
 *      1. agent keys that are found in the config file
 *      2. other agent keys
 *      3. keys that are only listed in the config file
 */
static void
pubkey_prepare(Authctxt *authctxt)
{
        Identity *id;
        Idlist agent, files, *preferred;
        Key *key;
        AuthenticationConnection *ac;
        char *comment;
        int i, found;

        TAILQ_INIT(&agent);     /* keys from the agent */
        TAILQ_INIT(&files);     /* keys from the config file */
        preferred = &authctxt->keys;
        TAILQ_INIT(preferred);  /* preferred order of keys */

        /* list of keys stored in the filesystem */
        for (i = 0; i < options.num_identity_files; i++) {
                key = options.identity_keys[i];
                if (key && key->type == KEY_RSA1)
                        continue;
                options.identity_keys[i] = NULL;
                id = xmalloc(sizeof(*id));
                memset(id, 0, sizeof(*id));
                id->key = key;
                id->filename = xstrdup(options.identity_files[i]);
                TAILQ_INSERT_TAIL(&files, id, next);
        }
        /* list of keys supported by the agent */
        if ((ac = ssh_get_authentication_connection())) {
                for (key = ssh_get_first_identity(ac, &comment, 2);
                    key != NULL;
                    key = ssh_get_next_identity(ac, &comment, 2)) {
                        found = 0;
                        TAILQ_FOREACH(id, &files, next) {
                                /* agent keys from the config file are preferred */
                                if (key_equal(key, id->key)) {
                                        key_free(key);
                                        xfree(comment);
                                        TAILQ_REMOVE(&files, id, next);
                                        TAILQ_INSERT_TAIL(preferred, id, next);
                                        id->ac = ac;
                                        found = 1;
                                        break;
                                }
                        }
                        if (!found && !options.identities_only) {
                                id = xmalloc(sizeof(*id));
                                memset(id, 0, sizeof(*id));
                                id->key = key;
                                id->filename = comment;
                                id->ac = ac;
                                TAILQ_INSERT_TAIL(&agent, id, next);
                        }
                }
                /* append remaining agent keys */
                for (id = TAILQ_FIRST(&agent); id; id = TAILQ_FIRST(&agent)) {
                        TAILQ_REMOVE(&agent, id, next);
                        TAILQ_INSERT_TAIL(preferred, id, next);
                }
                authctxt->agent = ac;
        }
        /* append remaining keys from the config file */
        for (id = TAILQ_FIRST(&files); id; id = TAILQ_FIRST(&files)) {
                TAILQ_REMOVE(&files, id, next);
                TAILQ_INSERT_TAIL(preferred, id, next);
        }
        TAILQ_FOREACH(id, preferred, next) {
                debug2("key: %s (%p)", id->filename, id->key);
        }
}

static void
pubkey_cleanup(Authctxt *authctxt)
{
        Identity *id;

        if (authctxt->agent != NULL)
                ssh_close_authentication_connection(authctxt->agent);
        for (id = TAILQ_FIRST(&authctxt->keys); id;
            id = TAILQ_FIRST(&authctxt->keys)) {
                TAILQ_REMOVE(&authctxt->keys, id, next);
                if (id->key)
                        key_free(id->key);
                if (id->filename)
                        xfree(id->filename);
                xfree(id);
        }
}

int
userauth_pubkey(Authctxt *authctxt)
{
        Identity *id;
        int sent = 0;

        while ((id = TAILQ_FIRST(&authctxt->keys))) {
                if (id->tried++)
                        return (0);
                /* move key to the end of the queue */
                TAILQ_REMOVE(&authctxt->keys, id, next);
                TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
                /*
                 * send a test message if we have the public key. for
                 * encrypted keys we cannot do this and have to load the
                 * private key instead
                 */
                if (id->key && id->key->type != KEY_RSA1) {
                        debug("Offering public key: %s", id->filename);
                        sent = send_pubkey_test(authctxt, id);
                } else if (id->key == NULL) {
                        debug("Trying private key: %s", id->filename);
                        id->key = load_identity_file(id->filename);
                        if (id->key != NULL) {
                                id->isprivate = 1;
                                sent = sign_and_send_pubkey(authctxt, id);
                                key_free(id->key);
                                id->key = NULL;
                        }
                }
                if (sent)
                        return (sent);
        }
        return (0);
}

/*
 * Send userauth request message specifying keyboard-interactive method.
 */
int
userauth_kbdint(Authctxt *authctxt)
{
        static int attempt = 0;

        if (attempt++ >= options.number_of_password_prompts)
                return 0;
        /* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
        if (attempt > 1 && !authctxt->info_req_seen) {
                debug3("userauth_kbdint: disable: no info_req_seen");
                dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
                return 0;
        }

        debug2("userauth_kbdint");
        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_cstring(authctxt->server_user);
        packet_put_cstring(authctxt->service);
        packet_put_cstring(authctxt->method->name);
        packet_put_cstring("");                                 /* lang */
        packet_put_cstring(options.kbd_interactive_devices ?
            options.kbd_interactive_devices : "");
        packet_send();

        dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
        return 1;
}

/*
 * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
 */
void
input_userauth_info_req(int type, u_int32_t seq, void *ctxt)
{
        Authctxt *authctxt = ctxt;
        char *name, *inst, *lang, *prompt, *response;
        u_int num_prompts, i;
        int echo = 0;

        debug2("input_userauth_info_req");

        if (authctxt == NULL)
                fatal("input_userauth_info_req: no authentication context");

        authctxt->info_req_seen = 1;

        name = packet_get_string(NULL);
        inst = packet_get_string(NULL);
        lang = packet_get_string(NULL);
        if (strlen(name) > 0)
                logit("%s", name);
        if (strlen(inst) > 0)
                logit("%s", inst);
        xfree(name);
        xfree(inst);
        xfree(lang);

        num_prompts = packet_get_int();
        /*
         * Begin to build info response packet based on prompts requested.
         * We commit to providing the correct number of responses, so if
         * further on we run into a problem that prevents this, we have to
         * be sure and clean this up and send a correct error response.
         */
        packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
        packet_put_int(num_prompts);

        debug2("input_userauth_info_req: num_prompts %d", num_prompts);
        for (i = 0; i < num_prompts; i++) {
                prompt = packet_get_string(NULL);
                echo = packet_get_char();

                response = read_passphrase(prompt, echo ? RP_ECHO : 0);

                packet_put_cstring(response);
                memset(response, 0, strlen(response));
                xfree(response);
                xfree(prompt);
        }
        packet_check_eom(); /* done with parsing incoming message. */

        packet_add_padding(64);
        packet_send();
}

static int
ssh_keysign(Key *key, u_char **sigp, u_int *lenp,
    u_char *data, u_int datalen)
{
        Buffer b;
        struct stat st;
        pid_t pid;
        int to[2], from[2], status, version = 2;

        debug2("ssh_keysign called");

        if (stat(_PATH_SSH_KEY_SIGN, &st) < 0) {
                error("ssh_keysign: no installed: %s", strerror(errno));
                return -1;
        }
        if (fflush(stdout) != 0)
                error("ssh_keysign: fflush: %s", strerror(errno));
        if (pipe(to) < 0) {
                error("ssh_keysign: pipe: %s", strerror(errno));
                return -1;
        }
        if (pipe(from) < 0) {
                error("ssh_keysign: pipe: %s", strerror(errno));
                return -1;
        }
        if ((pid = fork()) < 0) {
                error("ssh_keysign: fork: %s", strerror(errno));
                return -1;
        }
        if (pid == 0) {
                seteuid(getuid());
                setuid(getuid());
                close(from[0]);
                if (dup2(from[1], STDOUT_FILENO) < 0)
                        fatal("ssh_keysign: dup2: %s", strerror(errno));
                close(to[1]);
                if (dup2(to[0], STDIN_FILENO) < 0)
                        fatal("ssh_keysign: dup2: %s", strerror(errno));
                close(from[1]);
                close(to[0]);
                execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *) 0);
                fatal("ssh_keysign: exec(%s): %s", _PATH_SSH_KEY_SIGN,
                    strerror(errno));
        }
        close(from[1]);
        close(to[0]);

        buffer_init(&b);
        buffer_put_int(&b, packet_get_connection_in()); /* send # of socket */
        buffer_put_string(&b, data, datalen);
        if (ssh_msg_send(to[1], version, &b) == -1)
                fatal("ssh_keysign: couldn't send request");

        if (ssh_msg_recv(from[0], &b) < 0) {
                error("ssh_keysign: no reply");
                buffer_free(&b);
                return -1;
        }
        close(from[0]);
        close(to[1]);

        while (waitpid(pid, &status, 0) < 0)
                if (errno != EINTR)
                        break;

        if (buffer_get_char(&b) != version) {
                error("ssh_keysign: bad version");
                buffer_free(&b);
                return -1;
        }
        *sigp = buffer_get_string(&b, lenp);
        buffer_free(&b);

        return 0;
}

int
userauth_hostbased(Authctxt *authctxt)
{
        Key *private = NULL;
        Sensitive *sensitive = authctxt->sensitive;
        Buffer b;
        u_char *signature, *blob;
        char *chost, *pkalg, *p;
        const char *service;
        u_int blen, slen;
        int ok, i, len, found = 0;

        /* check for a useful key */
        for (i = 0; i < sensitive->nkeys; i++) {
                private = sensitive->keys[i];
                if (private && private->type != KEY_RSA1) {
                        found = 1;
                        /* we take and free the key */
                        sensitive->keys[i] = NULL;
                        break;
                }
        }
        if (!found) {
                debug("No more client hostkeys for hostbased authentication.");
                return 0;
        }
        if (key_to_blob(private, &blob, &blen) == 0) {
                key_free(private);
                return 0;
        }
        /* figure out a name for the client host */
        p = get_local_name(packet_get_connection_in());
        if (p == NULL) {
                error("userauth_hostbased: cannot get local ipaddr/name");
                key_free(private);
                return 0;
        }
        len = strlen(p) + 2;
        chost = xmalloc(len);
        strlcpy(chost, p, len);
        strlcat(chost, ".", len);
        debug2("userauth_hostbased: chost %s", chost);
        xfree(p);

        service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
            authctxt->service;
        pkalg = xstrdup(key_ssh_name(private));
        buffer_init(&b);
        /* construct data */
        buffer_put_string(&b, session_id2, session_id2_len);
        buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
        buffer_put_cstring(&b, authctxt->server_user);
        buffer_put_cstring(&b, service);
        buffer_put_cstring(&b, authctxt->method->name);
        buffer_put_cstring(&b, pkalg);
        buffer_put_string(&b, blob, blen);
        buffer_put_cstring(&b, chost);
        buffer_put_cstring(&b, authctxt->local_user);
#ifdef DEBUG_PK
        buffer_dump(&b);
#endif
        if (sensitive->external_keysign)
                ok = ssh_keysign(private, &signature, &slen,
                    buffer_ptr(&b), buffer_len(&b));
        else
                ok = key_sign(private, &signature, &slen,
                    buffer_ptr(&b), buffer_len(&b));
        key_free(private);
        buffer_free(&b);
        if (ok != 0) {
                error("key_sign failed");
                xfree(chost);
                xfree(pkalg);
                return 0;
        }
        packet_start(SSH2_MSG_USERAUTH_REQUEST);
        packet_put_cstring(authctxt->server_user);
        packet_put_cstring(authctxt->service);
        packet_put_cstring(authctxt->method->name);
        packet_put_cstring(pkalg);
        packet_put_string(blob, blen);
        packet_put_cstring(chost);
        packet_put_cstring(authctxt->local_user);
        packet_put_string(signature, slen);
        memset(signature, 's', slen);
        xfree(signature);
        xfree(chost);
        xfree(pkalg);

        packet_send();
        return 1;
}

/* find auth method */

/*
 * given auth method name, if configurable options permit this method fill
 * in auth_ident field and return true, otherwise return false.
 */
static int
authmethod_is_enabled(Authmethod *method)
{
        if (method == NULL)
                return 0;
        /* return false if options indicate this method is disabled */
        if  (method->enabled == NULL || *method->enabled == 0)
                return 0;
        /* return false if batch mode is enabled but method needs interactive mode */
        if  (method->batch_flag != NULL && *method->batch_flag != 0)
                return 0;
        return 1;
}

static Authmethod *
authmethod_lookup(const char *name)
{
        Authmethod *method = NULL;
        if (name != NULL)
                for (method = authmethods; method->name != NULL; method++)
                        if (strcmp(name, method->name) == 0)
                                return method;
        debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
        return NULL;
}

/* XXX internal state */
static Authmethod *current = NULL;
static char *supported = NULL;
static char *preferred = NULL;

/*
 * Given the authentication method list sent by the server, return the
 * next method we should try.  If the server initially sends a nil list,
 * use a built-in default list.
 */
static Authmethod *
authmethod_get(char *authlist)
{
        char *name = NULL;
        u_int next;

        /* Use a suitable default if we're passed a nil list.  */
        if (authlist == NULL || strlen(authlist) == 0)
                authlist = options.preferred_authentications;

        if (supported == NULL || strcmp(authlist, supported) != 0) {
                debug3("start over, passed a different list %s", authlist);
                if (supported != NULL)
                        xfree(supported);
                supported = xstrdup(authlist);
                preferred = options.preferred_authentications;
                debug3("preferred %s", preferred);
                current = NULL;
        } else if (current != NULL && authmethod_is_enabled(current))
                return current;

        for (;;) {
                if ((name = match_list(preferred, supported, &next)) == NULL) {
                        debug("No more authentication methods to try.");
                        current = NULL;
                        return NULL;
                }
                preferred += next;
                debug3("authmethod_lookup %s", name);
                debug3("remaining preferred: %s", preferred);
                if ((current = authmethod_lookup(name)) != NULL &&
                    authmethod_is_enabled(current)) {
                        debug3("authmethod_is_enabled %s", name);
                        debug("Next authentication method: %s", name);
                        return current;
                }
        }
}

static char *
authmethods_get(void)
{
        Authmethod *method = NULL;
        Buffer b;
        char *list;

        buffer_init(&b);
        for (method = authmethods; method->name != NULL; method++) {
                if (authmethod_is_enabled(method)) {
                        if (buffer_len(&b) > 0)
                                buffer_append(&b, ",", 1);
                        buffer_append(&b, method->name, strlen(method->name));
                }
        }
        buffer_append(&b, "\0", 1);
        list = xstrdup(buffer_ptr(&b));
        buffer_free(&b);
        return list;
}