/*
 *  Off-the-Record Messaging library
 *  Copyright (C) 2004-2014  Ian Goldberg, David Goulet, Rob Smits,
 *                           Chris Alexander, Willy Lew, Lisa Du,
 *                           Nikita Borisov
 *                           <otr@cypherpunks.ca>
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of version 2.1 of the GNU Lesser General
 *  Public License as published by the Free Software Foundation.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/* system headers */
#include <stdlib.h>
#include <string.h>
#include <assert.h>

/* libotr headers */
#include "b64.h"
#include "privkey.h"
#include "auth.h"
#include "serial.h"
#include "proto.h"
#include "context.h"
#include "mem.h"

#if OTRL_DEBUGGING
#include <stdio.h>

/* Dump the contents of an OtrlAuthInfo to the FILE *f. */
void otrl_auth_dump(FILE *f, const OtrlAuthInfo *auth)
{
    int i;

    fprintf(f, "  Auth info %p:\n", auth);
    fprintf(f, "    State: %d (%s)\n", auth->authstate,
	auth->authstate == OTRL_AUTHSTATE_NONE ? "NONE" :
	auth->authstate == OTRL_AUTHSTATE_AWAITING_DHKEY ? "AWAITING_DHKEY" :
	auth->authstate == OTRL_AUTHSTATE_AWAITING_REVEALSIG ?
	    "AWAITING_REVEALSIG" :
	auth->authstate == OTRL_AUTHSTATE_AWAITING_SIG ? "AWAITING_SIG" :
	auth->authstate == OTRL_AUTHSTATE_V1_SETUP ? "V1_SETUP" :
	"INVALID");
    fprintf(f, "    Context: %p\n", auth->context);
    fprintf(f, "    Our keyid:   %u\n", auth->our_keyid);
    fprintf(f, "    Their keyid: %u\n", auth->their_keyid);
    fprintf(f, "    Their fingerprint: ");
    for (i=0;i<20;++i) {
	fprintf(f, "%02x", auth->their_fingerprint[i]);
    }
    fprintf(f, "\n    Initiated = %d\n", auth->initiated);
    fprintf(f, "\n    Proto version = %d\n", auth->protocol_version);
    fprintf(f, "\n    Lastauthmsg = %s\n",
	auth->lastauthmsg ? auth->lastauthmsg : "(nil)");
    fprintf(f, "\n    Commit sent time = %ld\n",
	(long) auth->commit_sent_time);
}

#endif

/*
 * Initialize the fields of an OtrlAuthInfo (already allocated).
 */
void otrl_auth_new(struct context *context)
{
    OtrlAuthInfo *auth = &(context->auth);
    auth->authstate = OTRL_AUTHSTATE_NONE;
    otrl_dh_keypair_init(&(auth->our_dh));
    auth->our_keyid = 0;
    auth->encgx = NULL;
    auth->encgx_len = 0;
    memset(auth->r, 0, 16);
    memset(auth->hashgx, 0, 32);
    auth->their_pub = NULL;
    auth->their_keyid = 0;
    auth->enc_c = NULL;
    auth->enc_cp = NULL;
    auth->mac_m1 = NULL;
    auth->mac_m1p = NULL;
    auth->mac_m2 = NULL;
    auth->mac_m2p = NULL;
    memset(auth->their_fingerprint, 0, 20);
    auth->initiated = 0;
    auth->protocol_version = 0;
    memset(auth->secure_session_id, 0, 20);
    auth->secure_session_id_len = 0;
    auth->lastauthmsg = NULL;
    auth->commit_sent_time = 0;
    auth->context = context;
}

/*
 * Clear the fields of an OtrlAuthInfo (but leave it allocated).
 */
void otrl_auth_clear(OtrlAuthInfo *auth)
{
    auth->authstate = OTRL_AUTHSTATE_NONE;
    otrl_dh_keypair_free(&(auth->our_dh));
    auth->our_keyid = 0;
    free(auth->encgx);
    auth->encgx = NULL;
    auth->encgx_len = 0;
    memset(auth->r, 0, 16);
    memset(auth->hashgx, 0, 32);
    gcry_mpi_release(auth->their_pub);
    auth->their_pub = NULL;
    auth->their_keyid = 0;
    gcry_cipher_close(auth->enc_c);
    gcry_cipher_close(auth->enc_cp);
    gcry_md_close(auth->mac_m1);
    gcry_md_close(auth->mac_m1p);
    gcry_md_close(auth->mac_m2);
    gcry_md_close(auth->mac_m2p);
    auth->enc_c = NULL;
    auth->enc_cp = NULL;
    auth->mac_m1 = NULL;
    auth->mac_m1p = NULL;
    auth->mac_m2 = NULL;
    auth->mac_m2p = NULL;
    memset(auth->their_fingerprint, 0, 20);
    auth->initiated = 0;
    auth->protocol_version = 0;
    memset(auth->secure_session_id, 0, 20);
    auth->secure_session_id_len = 0;
    free(auth->lastauthmsg);
    auth->lastauthmsg = NULL;
    auth->commit_sent_time = 0;
}

/*
 * Start a fresh AKE (version 2 or 3) using the given OtrlAuthInfo.  Generate
 * a fresh DH keypair to use.  If no error is returned, the message to
 * transmit will be contained in auth->lastauthmsg.
 */
gcry_error_t otrl_auth_start_v23(OtrlAuthInfo *auth, int version)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    const enum gcry_mpi_format format = GCRYMPI_FMT_USG;
    size_t npub;
    gcry_cipher_hd_t enc = NULL;
    unsigned char ctr[16];
    unsigned char *buf, *bufp;
    size_t buflen, lenp;

    /* Clear out this OtrlAuthInfo and start over */
    otrl_auth_clear(auth);
    auth->initiated = 1;
    auth->protocol_version = version;
    auth->context->protocol_version = version;

    otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh));
    auth->our_keyid = 1;

    /* Pick an encryption key */
    gcry_randomize(auth->r, 16, GCRY_STRONG_RANDOM);

    /* Allocate space for the encrypted g^x */
    gcry_mpi_print(format, NULL, 0, &npub, auth->our_dh.pub);
    auth->encgx = malloc(4+npub);
    if (auth->encgx == NULL) goto memerr;
    auth->encgx_len = 4+npub;
    bufp = auth->encgx;
    lenp = auth->encgx_len;
    write_mpi(auth->our_dh.pub, npub, "g^x");
    assert(lenp == 0);

    /* Hash g^x */
    gcry_md_hash_buffer(GCRY_MD_SHA256, auth->hashgx, auth->encgx,
	    auth->encgx_len);

    /* Encrypt g^x using the key r */
    err = gcry_cipher_open(&enc, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR,
	    GCRY_CIPHER_SECURE);
    if (err) goto err;

    err = gcry_cipher_setkey(enc, auth->r, 16);
    if (err) goto err;

    memset(ctr, 0, 16);
    err = gcry_cipher_setctr(enc, ctr, 16);
    if (err) goto err;

    err = gcry_cipher_encrypt(enc, auth->encgx, auth->encgx_len, NULL, 0);
    if (err) goto err;

    gcry_cipher_close(enc);
    enc = NULL;

    /* Now serialize the message */
    lenp = OTRL_HEADER_LEN + (auth->protocol_version == 3 ? 8 : 0) + 4
	    + auth->encgx_len + 4 + 32;
    bufp = malloc(lenp);
    if (bufp == NULL) goto memerr;
    buf = bufp;
    buflen = lenp;

    /* Header */
    write_header(auth->protocol_version, '\x02');
    if (auth->protocol_version == 3) {
	/* instance tags */
	write_int(auth->context->our_instance);
	debug_int("Sender instag", bufp-4);
	write_int(auth->context->their_instance);
	debug_int("Recipient instag", bufp-4);
    }

    /* Encrypted g^x */
    write_int(auth->encgx_len);
    debug_int("Enc gx len", bufp-4);
    memmove(bufp, auth->encgx, auth->encgx_len);
    debug_data("Enc gx", bufp, auth->encgx_len);
    bufp += auth->encgx_len; lenp -= auth->encgx_len;

    /* Hashed g^x */
    write_int(32);
    debug_int("hashgx len", bufp-4);
    memmove(bufp, auth->hashgx, 32);
    debug_data("hashgx", bufp, 32);
    bufp += 32; lenp -= 32;

    assert(lenp == 0);

    auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen);
    free(buf);
    if (auth->lastauthmsg == NULL) goto memerr;
    auth->authstate = OTRL_AUTHSTATE_AWAITING_DHKEY;

    return err;

memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    otrl_auth_clear(auth);
    gcry_cipher_close(enc);
    return err;
}

/*
 * Create a D-H Key Message using the our_dh value in the given auth,
 * and store it in auth->lastauthmsg.
 */
static gcry_error_t create_key_message(OtrlAuthInfo *auth)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    const enum gcry_mpi_format format = GCRYMPI_FMT_USG;
    unsigned char *buf, *bufp;
    size_t buflen, lenp;
    size_t npub;

    gcry_mpi_print(format, NULL, 0, &npub, auth->our_dh.pub);
    buflen = OTRL_HEADER_LEN + (auth->protocol_version == 3 ? 8 : 0) + 4 + npub;
    buf = malloc(buflen);
    if (buf == NULL) goto memerr;
    bufp = buf;
    lenp = buflen;

    /* header */
    write_header(auth->protocol_version, '\x0a');
    if (auth->protocol_version == 3) {
	/* instance tags */
	write_int(auth->context->our_instance);
	debug_int("Sender instag", bufp-4);
	write_int(auth->context->their_instance);
	debug_int("Recipient instag", bufp-4);
    }

    /* g^y */
    write_mpi(auth->our_dh.pub, npub, "g^y");

    assert(lenp == 0);

    free(auth->lastauthmsg);
    auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen);
    free(buf);
    if (auth->lastauthmsg == NULL) goto memerr;

    return err;

memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
    return err;
}

/*
 * Handle an incoming D-H Commit Message.  If no error is returned, the
 * message to send will be left in auth->lastauthmsg.  Generate a fresh
 * keypair to use.
 */
gcry_error_t otrl_auth_handle_commit(OtrlAuthInfo *auth,
	const char *commitmsg, int version)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    unsigned char *buf = NULL, *bufp = NULL, *encbuf = NULL;
    unsigned char hashbuf[32];
    size_t buflen, lenp, enclen, hashlen;
    int res;

    /* Are we the auth for the master context? */
    int is_master = (auth->context->m_context == auth->context);

    res = otrl_base64_otr_decode(commitmsg, &buf, &buflen);
    if (res == -1) goto memerr;
    if (res == -2) goto invval;

    bufp = buf;
    lenp = buflen;

    /* Header */
    auth->protocol_version = version;
    auth->context->protocol_version = version;
    skip_header('\x02');

    if (version == 3) {
	require_len(8);
	bufp += 8; lenp -= 8;
    }

    /* Encrypted g^x */
    read_int(enclen);
    require_len(enclen);
    encbuf = malloc(enclen);
    if (encbuf == NULL && enclen > 0) goto memerr;
    memmove(encbuf, bufp, enclen);
    bufp += enclen; lenp -= enclen;

    /* Hashed g^x */
    read_int(hashlen);
    if (hashlen != 32) goto invval;
    require_len(32);
    memmove(hashbuf, bufp, 32);
    bufp += 32; lenp -= 32;

    if (lenp != 0) goto invval;
    free(buf);
    buf = NULL;

    switch(auth->authstate) {
	case OTRL_AUTHSTATE_NONE:
	case OTRL_AUTHSTATE_AWAITING_SIG:
	case OTRL_AUTHSTATE_V1_SETUP:
	    /* Store the incoming information */
	    otrl_auth_clear(auth);
	    auth->protocol_version = version;

	    otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh));

	    auth->our_keyid = 1;
	    auth->encgx = encbuf;
	    encbuf = NULL;
	    auth->encgx_len = enclen;
	    memmove(auth->hashgx, hashbuf, 32);

	    /* Create a D-H Key Message */
	    err = create_key_message(auth);
	    if (err) goto err;
	    auth->authstate = OTRL_AUTHSTATE_AWAITING_REVEALSIG;
	    break;

	case OTRL_AUTHSTATE_AWAITING_DHKEY:
	    /* We sent a D-H Commit Message, and we also received one
	     * back.  If we're the master context, then the keypair in here
	     * is probably stale; we just kept it around for a little
	     * while in case some other logged in instance of our buddy
	     * replied with a DHKEY message.  In that case, use the
	     * incoming parameters.  Otherwise, compare the hashgx
	     * values to see which one wins.
	     *
	     * This does NOT use constant time comparison because these
	     * are two public values thus don't need it. Also, this checks
	     * which pubkey is larger and not if they are the same. */
	    if (!is_master && memcmp(auth->hashgx, hashbuf, 32) > 0) {
		/* Ours wins.  Ignore the message we received, and just
		 * resend the same D-H Commit message again. */
		free(encbuf);
		encbuf = NULL;
	    } else {
		/* Ours loses.  Use the incoming parameters instead. */
		otrl_auth_clear(auth);
		auth->protocol_version = version;
		otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh));
		auth->our_keyid = 1;
		auth->encgx = encbuf;
		encbuf = NULL;
		auth->encgx_len = enclen;
		memmove(auth->hashgx, hashbuf, 32);

		/* Create a D-H Key Message */
		err = create_key_message(auth);
		if (err) goto err;
		auth->authstate = OTRL_AUTHSTATE_AWAITING_REVEALSIG;
	    }
	    break;
	case OTRL_AUTHSTATE_AWAITING_REVEALSIG:
	    /* Use the incoming parameters, but just retransmit the old
	     * D-H Key Message. */
	    free(auth->encgx);
	    auth->encgx = encbuf;
	    encbuf = NULL;
	    auth->encgx_len = enclen;
	    memmove(auth->hashgx, hashbuf, 32);
	    break;
    }

    return err;

invval:
    err = gcry_error(GPG_ERR_INV_VALUE);
    goto err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    free(encbuf);
    return err;
}

/*
 * Calculate the encrypted part of the Reveal Signature and Signature
 * Messages, given a MAC key, an encryption key, two DH public keys, an
 * authentication public key (contained in an OtrlPrivKey structure),
 * and a keyid.  If no error is returned, *authbufp will point to the
 * result, and *authlenp will point to its length.
 */
static gcry_error_t calculate_pubkey_auth(unsigned char **authbufp,
	size_t *authlenp, gcry_md_hd_t mackey, gcry_cipher_hd_t enckey,
	gcry_mpi_t our_dh_pub, gcry_mpi_t their_dh_pub,
	OtrlPrivKey *privkey, unsigned int keyid)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    const enum gcry_mpi_format format = GCRYMPI_FMT_USG;
    size_t ourpublen, theirpublen, totallen, lenp;
    unsigned char *buf = NULL, *bufp = NULL;
    unsigned char macbuf[32];
    unsigned char *sigbuf = NULL;
    size_t siglen;

    /* How big are the DH public keys? */
    gcry_mpi_print(format, NULL, 0, &ourpublen, our_dh_pub);
    gcry_mpi_print(format, NULL, 0, &theirpublen, their_dh_pub);

    /* How big is the total structure to be MAC'd? */
    totallen = 4 + ourpublen + 4 + theirpublen + 2 + privkey->pubkey_datalen
	    + 4;
    buf = malloc(totallen);
    if (buf == NULL) goto memerr;

    bufp = buf;
    lenp = totallen;

    /* Write the data to be MAC'd */
    write_mpi(our_dh_pub, ourpublen, "Our DH pubkey");
    write_mpi(their_dh_pub, theirpublen, "Their DH pubkey");
    bufp[0] = ((privkey->pubkey_type) >> 8) & 0xff;
    bufp[1] = (privkey->pubkey_type) & 0xff;
    bufp += 2; lenp -= 2;
    memmove(bufp, privkey->pubkey_data, privkey->pubkey_datalen);
    debug_data("Pubkey", bufp, privkey->pubkey_datalen);
    bufp += privkey->pubkey_datalen; lenp -= privkey->pubkey_datalen;
    write_int(keyid);
    debug_int("Keyid", bufp-4);

    assert(lenp == 0);

    /* Do the MAC */
    gcry_md_reset(mackey);
    gcry_md_write(mackey, buf, totallen);
    memmove(macbuf, gcry_md_read(mackey, GCRY_MD_SHA256), 32);

    free(buf);
    buf = NULL;

    /* Sign the MAC */
    err = otrl_privkey_sign(&sigbuf, &siglen, privkey, macbuf, 32);
    if (err) goto err;

    /* Calculate the total size of the structure to be encrypted */
    totallen = 2 + privkey->pubkey_datalen + 4 + siglen;
    buf = malloc(totallen);
    if (buf == NULL) goto memerr;
    bufp = buf;
    lenp = totallen;

    /* Write the data to be encrypted */
    bufp[0] = ((privkey->pubkey_type) >> 8) & 0xff;
    bufp[1] = (privkey->pubkey_type) & 0xff;
    bufp += 2; lenp -= 2;
    memmove(bufp, privkey->pubkey_data, privkey->pubkey_datalen);
    debug_data("Pubkey", bufp, privkey->pubkey_datalen);
    bufp += privkey->pubkey_datalen; lenp -= privkey->pubkey_datalen;
    write_int(keyid);
    debug_int("Keyid", bufp-4);
    memmove(bufp, sigbuf, siglen);
    debug_data("Signature", bufp, siglen);
    bufp += siglen; lenp -= siglen;
    free(sigbuf);
    sigbuf = NULL;

    assert(lenp == 0);

    /* Now do the encryption */
    err = gcry_cipher_encrypt(enckey, buf, totallen, NULL, 0);
    if (err) goto err;

    *authbufp = buf;
    buf = NULL;
    *authlenp = totallen;

    return err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    free(sigbuf);
    return err;
}

/*
 * Decrypt the authenticator in the Reveal Signature and Signature
 * Messages, given a MAC key, and encryption key, and two DH public
 * keys.  The fingerprint of the received public key will get put into
 * fingerprintbufp, and the received keyid will get put in *keyidp.
 * The encrypted data pointed to by authbuf will be decrypted in place.
 */
static gcry_error_t check_pubkey_auth(unsigned char fingerprintbufp[20],
	unsigned int *keyidp, unsigned char *authbuf, size_t authlen,
	gcry_md_hd_t mackey, gcry_cipher_hd_t enckey,
	gcry_mpi_t our_dh_pub, gcry_mpi_t their_dh_pub)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    const enum gcry_mpi_format format = GCRYMPI_FMT_USG;
    size_t ourpublen, theirpublen, totallen, lenp;
    unsigned char *buf = NULL, *bufp = NULL;
    unsigned char macbuf[32];
    unsigned short pubkey_type;
    gcry_mpi_t p,q,g,y;
    gcry_sexp_t pubs = NULL;
    unsigned int received_keyid;
    unsigned char *fingerprintstart, *fingerprintend, *sigbuf;
    size_t siglen;

    /* Start by decrypting it */
    err = gcry_cipher_decrypt(enckey, authbuf, authlen, NULL, 0);
    if (err) goto err;

    bufp = authbuf;
    lenp = authlen;

    /* Get the public key and calculate its fingerprint */
    require_len(2);
    pubkey_type = (bufp[0] << 8) + bufp[1];
    bufp += 2; lenp -= 2;
    if (pubkey_type != OTRL_PUBKEY_TYPE_DSA) goto invval;
    fingerprintstart = bufp;
    read_mpi(p);
    read_mpi(q);
    read_mpi(g);
    read_mpi(y);
    fingerprintend = bufp;
    gcry_md_hash_buffer(GCRY_MD_SHA1, fingerprintbufp,
	    fingerprintstart, fingerprintend-fingerprintstart);
    gcry_sexp_build(&pubs, NULL,
	"(public-key (dsa (p %m)(q %m)(g %m)(y %m)))", p, q, g, y);
    gcry_mpi_release(p);
    gcry_mpi_release(q);
    gcry_mpi_release(g);
    gcry_mpi_release(y);

    /* Get the keyid */
    read_int(received_keyid);
    if (received_keyid == 0) goto invval;

    /* Get the signature */
    sigbuf = bufp;
    siglen = lenp;

    /* How big are the DH public keys? */
    gcry_mpi_print(format, NULL, 0, &ourpublen, our_dh_pub);
    gcry_mpi_print(format, NULL, 0, &theirpublen, their_dh_pub);

    /* Now calculate the message to be MAC'd. */
    totallen = 4 + ourpublen + 4 + theirpublen + 2 +
	(fingerprintend - fingerprintstart) + 4;
    buf = malloc(totallen);
    if (buf == NULL) goto memerr;

    bufp = buf;
    lenp = totallen;

    write_mpi(their_dh_pub, theirpublen, "Their DH pubkey");
    write_mpi(our_dh_pub, ourpublen, "Our DH pubkey");
    bufp[0] = (pubkey_type >> 8) & 0xff;
    bufp[1] = pubkey_type & 0xff;
    bufp += 2; lenp -= 2;
    memmove(bufp, fingerprintstart, fingerprintend - fingerprintstart);
    debug_data("Pubkey", bufp, fingerprintend - fingerprintstart);
    bufp += fingerprintend - fingerprintstart;
    lenp -= fingerprintend - fingerprintstart;
    write_int(received_keyid);
    debug_int("Keyid", bufp-4);

    assert(lenp == 0);

    /* Do the MAC */
    gcry_md_reset(mackey);
    gcry_md_write(mackey, buf, totallen);
    memmove(macbuf, gcry_md_read(mackey, GCRY_MD_SHA256), 32);

    free(buf);
    buf = NULL;

    /* Verify the signature on the MAC */
    err = otrl_privkey_verify(sigbuf, siglen, pubkey_type, pubs, macbuf, 32);
    if (err) goto err;
    gcry_sexp_release(pubs);
    pubs = NULL;

    /* Everything checked out */
    *keyidp = received_keyid;

    return err;
invval:
    err = gcry_error(GPG_ERR_INV_VALUE);
    goto err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    gcry_sexp_release(pubs);
    return err;
}

/*
 * Create a Reveal Signature Message using the values in the given auth,
 * and store it in auth->lastauthmsg.  Use the given privkey to sign the
 * message.
 */
static gcry_error_t create_revealsig_message(OtrlAuthInfo *auth,
	OtrlPrivKey *privkey)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    unsigned char *buf = NULL, *bufp, *startmac;
    size_t buflen, lenp;

    unsigned char *authbuf = NULL;
    size_t authlen;

    /* Get the encrypted authenticator */
    err = calculate_pubkey_auth(&authbuf, &authlen, auth->mac_m1, auth->enc_c,
	    auth->our_dh.pub, auth->their_pub, privkey, auth->our_keyid);
    if (err) goto err;

    buflen = OTRL_HEADER_LEN + (auth->protocol_version == 3 ? 8 : 0) + 4 + 16
	    + 4 + authlen + 20;
    buf = malloc(buflen);
    if (buf == NULL) goto memerr;

    bufp = buf;
    lenp = buflen;

    /* header */
    write_header(auth->protocol_version, '\x11');
    if (auth->protocol_version == 3) {
	/* instance tags */
	write_int(auth->context->our_instance);
	debug_int("Sender instag", bufp-4);
	write_int(auth->context->their_instance);
	debug_int("Recipient instag", bufp-4);
    }

    /* r */
    write_int(16);
    memmove(bufp, auth->r, 16);
    debug_data("r", bufp, 16);
    bufp += 16; lenp -= 16;

    /* Encrypted authenticator */
    startmac = bufp;
    write_int(authlen);
    memmove(bufp, authbuf, authlen);
    debug_data("auth", bufp, authlen);
    bufp += authlen; lenp -= authlen;
    free(authbuf);
    authbuf = NULL;

    /* MAC it, but only take the first 20 bytes */
    gcry_md_reset(auth->mac_m2);
    gcry_md_write(auth->mac_m2, startmac, bufp - startmac);
    memmove(bufp, gcry_md_read(auth->mac_m2, GCRY_MD_SHA256), 20);
    debug_data("MAC", bufp, 20);
    bufp += 20; lenp -= 20;

    assert(lenp == 0);

    free(auth->lastauthmsg);
    auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen);
    if (auth->lastauthmsg == NULL) goto memerr;
    free(buf);
    buf = NULL;

    return err;

memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    free(authbuf);
    return err;
}

/*
 * Create a Signature Message using the values in the given auth, and
 * store it in auth->lastauthmsg.  Use the given privkey to sign the
 * message.
 */
static gcry_error_t create_signature_message(OtrlAuthInfo *auth,
	OtrlPrivKey *privkey)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    unsigned char *buf = NULL, *bufp, *startmac;
    size_t buflen, lenp;

    unsigned char *authbuf = NULL;
    size_t authlen;

    /* Get the encrypted authenticator */
    err = calculate_pubkey_auth(&authbuf, &authlen, auth->mac_m1p,
	    auth->enc_cp, auth->our_dh.pub, auth->their_pub, privkey,
	    auth->our_keyid);
    if (err) goto err;

    buflen = OTRL_HEADER_LEN + (auth->protocol_version == 3 ? 8 : 0) + 4
	    + authlen + 20;
    buf = malloc(buflen);
    if (buf == NULL) goto memerr;

    bufp = buf;
    lenp = buflen;

    /* header */
    write_header(auth->protocol_version, '\x12');
    if (auth->protocol_version == 3) {
	/* instance tags */
	write_int(auth->context->our_instance);
	debug_int("Sender instag", bufp-4);
	write_int(auth->context->their_instance);
	debug_int("Recipient instag", bufp-4);
    }

    /* Encrypted authenticator */
    startmac = bufp;
    write_int(authlen);
    memmove(bufp, authbuf, authlen);
    debug_data("auth", bufp, authlen);
    bufp += authlen; lenp -= authlen;
    free(authbuf);
    authbuf = NULL;

    /* MAC it, but only take the first 20 bytes */
    gcry_md_reset(auth->mac_m2p);
    gcry_md_write(auth->mac_m2p, startmac, bufp - startmac);
    memmove(bufp, gcry_md_read(auth->mac_m2p, GCRY_MD_SHA256), 20);
    debug_data("MAC", bufp, 20);
    bufp += 20; lenp -= 20;

    assert(lenp == 0);

    free(auth->lastauthmsg);
    auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen);
    if (auth->lastauthmsg == NULL) goto memerr;
    free(buf);
    buf = NULL;

    return err;

memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    free(authbuf);
    return err;
}

/*
 * Handle an incoming D-H Key Message.  If no error is returned, and
 * *havemsgp is 1, the message to sent will be left in auth->lastauthmsg.
 * Use the given private authentication key to sign messages.
 */
gcry_error_t otrl_auth_handle_key(OtrlAuthInfo *auth, const char *keymsg,
	int *havemsgp, OtrlPrivKey *privkey)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    unsigned char *buf = NULL, *bufp = NULL;
    size_t buflen, lenp;
    gcry_mpi_t incoming_pub = NULL;
    int res;
    unsigned int msg_version;

    *havemsgp = 0;

    msg_version = otrl_proto_message_version(keymsg);

    res = otrl_base64_otr_decode(keymsg, &buf, &buflen);
    if (res == -1) goto memerr;
    if (res == -2) goto invval;

    bufp = buf;
    lenp = buflen;

    /* Header */
    skip_header('\x0a');

    if (msg_version == 3) {
	require_len(8);
	bufp += 8; lenp -= 8;
    }

    /* g^y */
    read_mpi(incoming_pub);

    if (lenp != 0) goto invval;
    free(buf);
    buf = NULL;

    switch(auth->authstate) {
	case OTRL_AUTHSTATE_AWAITING_DHKEY:
	    /* The other party may also be establishing a session with
	    another instance running a different version. Ignore any
	    DHKEY messages we aren't expecting. */
	    if (msg_version != auth->protocol_version) {
	      goto err;
	    }

	    /* Store the incoming public key */
	    gcry_mpi_release(auth->their_pub);
	    auth->their_pub = incoming_pub;
	    incoming_pub = NULL;

	    /* Compute the encryption and MAC keys */
	    err = otrl_dh_compute_v2_auth_keys(&(auth->our_dh),
		    auth->their_pub, auth->secure_session_id,
		    &(auth->secure_session_id_len),
		    &(auth->enc_c), &(auth->enc_cp),
		    &(auth->mac_m1), &(auth->mac_m1p),
		    &(auth->mac_m2), &(auth->mac_m2p));
	    if (err) goto err;

	    /* Create the Reveal Signature Message */
	    err = create_revealsig_message(auth, privkey);
	    if (err) goto err;
	    *havemsgp = 1;
	    auth->authstate = OTRL_AUTHSTATE_AWAITING_SIG;

	    break;

	case OTRL_AUTHSTATE_AWAITING_SIG:
	    if (gcry_mpi_cmp(incoming_pub, auth->their_pub) == 0) {
		/* Retransmit the Reveal Signature Message */
		*havemsgp = 1;
	    } else {
		/* Ignore this message */
		*havemsgp = 0;
	    }
	    break;
	case OTRL_AUTHSTATE_NONE:
	case OTRL_AUTHSTATE_AWAITING_REVEALSIG:
	case OTRL_AUTHSTATE_V1_SETUP:
	    /* Ignore this message */
	    *havemsgp = 0;
	    break;
    }

    gcry_mpi_release(incoming_pub);
    return err;

invval:
    err = gcry_error(GPG_ERR_INV_VALUE);
    goto err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    gcry_mpi_release(incoming_pub);
    return err;
}

/*
 * Handle an incoming Reveal Signature Message.  If no error is
 * returned, and *havemsgp is 1, the message to be sent will be left in
 * auth->lastauthmsg.  Use the given private authentication key to sign
 * messages.  Call the auth_succeeded callback if authentication is
 * successful.
 */
gcry_error_t otrl_auth_handle_revealsig(OtrlAuthInfo *auth,
	const char *revealmsg, int *havemsgp, OtrlPrivKey *privkey,
	gcry_error_t (*auth_succeeded)(const OtrlAuthInfo *auth, void *asdata),
	void *asdata)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    unsigned char *buf = NULL, *bufp = NULL, *gxbuf = NULL;
    unsigned char *authstart, *authend, *macstart;
    size_t buflen, lenp, rlen, authlen;
    gcry_cipher_hd_t enc = NULL;
    gcry_mpi_t incoming_pub = NULL;
    unsigned char ctr[16], hashbuf[32];
    int res;
    unsigned char version;

    *havemsgp = 0;

    res = otrl_base64_otr_decode(revealmsg, &buf, &buflen);
    if (res == -1) goto memerr;
    if (res == -2) goto invval;

    bufp = buf;
    lenp = buflen;

    require_len(3);
    version = bufp[1];

    /* Header */
    skip_header('\x11');

    if (version == 3) {
	require_len(8);
	bufp += 8; lenp -= 8;
    }

    /* r */
    read_int(rlen);
    if (rlen != 16) goto invval;
    require_len(rlen);
    memmove(auth->r, bufp, rlen);
    bufp += rlen; lenp -= rlen;

    /* auth */
    authstart = bufp;
    read_int(authlen);
    require_len(authlen);
    bufp += authlen; lenp -= authlen;
    authend = bufp;

    /* MAC */
    require_len(20);
    macstart = bufp;
    bufp += 20; lenp -= 20;

    if (lenp != 0) goto invval;

    switch(auth->authstate) {
	case OTRL_AUTHSTATE_AWAITING_REVEALSIG:
	    gxbuf = malloc(auth->encgx_len);
	    if (auth->encgx_len && gxbuf == NULL) goto memerr;

	    /* Use r to decrypt the value of g^x we received earlier */
	    err = gcry_cipher_open(&enc, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR,
		    GCRY_CIPHER_SECURE);
	    if (err) goto err;

	    err = gcry_cipher_setkey(enc, auth->r, 16);
	    if (err) goto err;

	    memset(ctr, 0, 16);
	    err = gcry_cipher_setctr(enc, ctr, 16);
	    if (err) goto err;

	    err = gcry_cipher_decrypt(enc, gxbuf, auth->encgx_len,
		    auth->encgx, auth->encgx_len);
	    if (err) goto err;

	    gcry_cipher_close(enc);
	    enc = NULL;

	    /* Check the hash */
	    gcry_md_hash_buffer(GCRY_MD_SHA256, hashbuf, gxbuf,
		    auth->encgx_len);
	    /* This isn't comparing secret data, but may as well use the
	     * constant-time version. */
	    if (otrl_mem_differ(hashbuf, auth->hashgx, 32)) goto decfail;

	    /* Extract g^x */
	    bufp = gxbuf;
	    lenp = auth->encgx_len;

	    read_mpi(incoming_pub);
	    free(gxbuf);
	    gxbuf = NULL;

	    if (lenp != 0) goto invval;

	    gcry_mpi_release(auth->their_pub);
	    auth->their_pub = incoming_pub;
	    incoming_pub = NULL;

	    /* Compute the encryption and MAC keys */
	    err = otrl_dh_compute_v2_auth_keys(&(auth->our_dh),
		    auth->their_pub, auth->secure_session_id,
		    &(auth->secure_session_id_len),
		    &(auth->enc_c), &(auth->enc_cp),
		    &(auth->mac_m1), &(auth->mac_m1p),
		    &(auth->mac_m2), &(auth->mac_m2p));
	    if (err) goto err;

	    /* Check the MAC */
	    gcry_md_reset(auth->mac_m2);
	    gcry_md_write(auth->mac_m2, authstart, authend - authstart);

	    if (otrl_mem_differ(macstart,
			gcry_md_read(auth->mac_m2, GCRY_MD_SHA256),
			20)) goto invval;

	    /* Check the auth */
	    err = check_pubkey_auth(auth->their_fingerprint,
		    &(auth->their_keyid), authstart + 4,
		    authend - authstart - 4, auth->mac_m1, auth->enc_c,
		    auth->our_dh.pub, auth->their_pub);
	    if (err) goto err;

	    authstart = NULL;
	    authend = NULL;
	    macstart = NULL;
	    free(buf);
	    buf = NULL;

	    /* Create the Signature Message */
	    err = create_signature_message(auth, privkey);
	    if (err) goto err;

	    /* No error?  Then we've completed our end of the
	     * authentication. */
	    auth->session_id_half = OTRL_SESSIONID_SECOND_HALF_BOLD;
	    if (auth_succeeded) err = auth_succeeded(auth, asdata);
	    *havemsgp = 1;
	    auth->our_keyid = 0;
	    auth->authstate = OTRL_AUTHSTATE_NONE;

	    break;
	case OTRL_AUTHSTATE_NONE:
	case OTRL_AUTHSTATE_AWAITING_DHKEY:
	case OTRL_AUTHSTATE_AWAITING_SIG:
	case OTRL_AUTHSTATE_V1_SETUP:
	    /* Ignore this message */
	    *havemsgp = 0;
	    free(buf);
	    buf = NULL;
	    break;
    }

    return err;

decfail:
    err = gcry_error(GPG_ERR_NO_ERROR);
    goto err;
invval:
    err = gcry_error(GPG_ERR_INV_VALUE);
    goto err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    free(gxbuf);
    gcry_cipher_close(enc);
    gcry_mpi_release(incoming_pub);
    return err;
}

/*
 * Handle an incoming Signature Message.  If no error is returned, and
 * *havemsgp is 1, the message to be sent will be left in
 * auth->lastauthmsg.  Call the auth_succeeded callback if
 * authentication is successful.
 */
gcry_error_t otrl_auth_handle_signature(OtrlAuthInfo *auth,
	const char *sigmsg, int *havemsgp,
	gcry_error_t (*auth_succeeded)(const OtrlAuthInfo *auth, void *asdata),
	void *asdata)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    unsigned char *buf = NULL, *bufp = NULL;
    unsigned char *authstart, *authend, *macstart;
    size_t buflen, lenp, authlen;
    int res;
    unsigned char version;

    *havemsgp = 0;

    res = otrl_base64_otr_decode(sigmsg, &buf, &buflen);
    if (res == -1) goto memerr;
    if (res == -2) goto invval;

    bufp = buf;
    lenp = buflen;

    require_len(3);
    version = bufp[1];

    /* Header */
    skip_header('\x12');

    if (version == 3) {
	require_len(8);
	bufp += 8; lenp -= 8;
    }

    /* auth */
    authstart = bufp;
    read_int(authlen);
    require_len(authlen);
    bufp += authlen; lenp -= authlen;
    authend = bufp;

    /* MAC */
    require_len(20);
    macstart = bufp;
    bufp += 20; lenp -= 20;

    if (lenp != 0) goto invval;

    switch(auth->authstate) {
	case OTRL_AUTHSTATE_AWAITING_SIG:
	    /* Check the MAC */
	    gcry_md_reset(auth->mac_m2p);
	    gcry_md_write(auth->mac_m2p, authstart, authend - authstart);
	    if (otrl_mem_differ(macstart,
			gcry_md_read(auth->mac_m2p, GCRY_MD_SHA256),
			20)) goto invval;

	    /* Check the auth */
	    err = check_pubkey_auth(auth->their_fingerprint,
		    &(auth->their_keyid), authstart + 4,
		    authend - authstart - 4, auth->mac_m1p, auth->enc_cp,
		    auth->our_dh.pub, auth->their_pub);
	    if (err) goto err;

	    authstart = NULL;
	    authend = NULL;
	    macstart = NULL;
	    free(buf);
	    buf = NULL;

	    /* No error?  Then we've completed our end of the
	     * authentication. */
	    auth->session_id_half = OTRL_SESSIONID_FIRST_HALF_BOLD;
	    if (auth_succeeded) err = auth_succeeded(auth, asdata);
	    free(auth->lastauthmsg);
	    auth->lastauthmsg = NULL;
	    *havemsgp = 0;
	    auth->our_keyid = 0;
	    auth->authstate = OTRL_AUTHSTATE_NONE;

	    break;
	case OTRL_AUTHSTATE_NONE:
	case OTRL_AUTHSTATE_AWAITING_DHKEY:
	case OTRL_AUTHSTATE_AWAITING_REVEALSIG:
	case OTRL_AUTHSTATE_V1_SETUP:
	    /* Ignore this message */
	    *havemsgp = 0;
	    free(buf);
	    buf = NULL;
	    break;
    }

    return err;

invval:
    err = gcry_error(GPG_ERR_INV_VALUE);
    goto err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    return err;
}

/* Version 1 routines, for compatibility */

/*
 * Create a verion 1 Key Exchange Message using the values in the given
 * auth, and store it in auth->lastauthmsg.  Set the Reply field to the
 * given value, and use the given privkey to sign the message.
 */
static gcry_error_t create_v1_key_exchange_message(OtrlAuthInfo *auth,
	unsigned char reply, OtrlPrivKey *privkey)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    const enum gcry_mpi_format format = GCRYMPI_FMT_USG;
    unsigned char *buf = NULL, *bufp = NULL, *sigbuf = NULL;
    size_t lenp, ourpublen, totallen, siglen;
    unsigned char hashbuf[20];

    if (privkey->pubkey_type != OTRL_PUBKEY_TYPE_DSA) {
	return gpg_error(GPG_ERR_INV_VALUE);
    }

    /* How big is the DH public key? */
    gcry_mpi_print(format, NULL, 0, &ourpublen, auth->our_dh.pub);

    totallen = 3 + 1 + privkey->pubkey_datalen + 4 + 4 + ourpublen + 40;
    buf = malloc(totallen);
    if (buf == NULL) goto memerr;

    bufp = buf;
    lenp = totallen;

    memmove(bufp, "\x00\x01\x0a", 3); /* header */
    debug_data("Header", bufp, 3);
    bufp += 3; lenp -= 3;

    bufp[0] = reply;
    debug_data("Reply", bufp, 1);
    bufp += 1; lenp -= 1;

    memmove(bufp, privkey->pubkey_data, privkey->pubkey_datalen);
    debug_data("Pubkey", bufp, privkey->pubkey_datalen);
    bufp += privkey->pubkey_datalen; lenp -= privkey->pubkey_datalen;

    write_int(auth->our_keyid);
    debug_int("Keyid", bufp-4);

    write_mpi(auth->our_dh.pub, ourpublen, "D-H y");

    /* Hash all the data written so far, and sign the hash */
    gcry_md_hash_buffer(GCRY_MD_SHA1, hashbuf, buf, bufp - buf);

    err = otrl_privkey_sign(&sigbuf, &siglen, privkey, hashbuf, 20);
    if (err) goto err;

    if (siglen != 40) goto invval;
    memmove(bufp, sigbuf, 40);
    debug_data("Signature", bufp, 40);
    bufp += 40; lenp -= 40;
    free(sigbuf);
    sigbuf = NULL;

    assert(lenp == 0);

    free(auth->lastauthmsg);
    auth->lastauthmsg = otrl_base64_otr_encode(buf, totallen);
    if (auth->lastauthmsg == NULL) goto memerr;
    free(buf);
    buf = NULL;

    return err;

invval:
    err = gcry_error(GPG_ERR_INV_VALUE);
    goto err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    free(sigbuf);
    return err;
}

/*
 * Start a fresh AKE (version 1) using the given OtrlAuthInfo.  If
 * our_dh is NULL, generate a fresh DH keypair to use.  Otherwise, use a
 * copy of the one passed (with the given keyid).  Use the given private
 * key to sign the message.  If no error is returned, the message to
 * transmit will be contained in auth->lastauthmsg.
 */
gcry_error_t otrl_auth_start_v1(OtrlAuthInfo *auth, DH_keypair *our_dh,
	unsigned int our_keyid, OtrlPrivKey *privkey)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);

    /* Clear out this OtrlAuthInfo and start over */
    otrl_auth_clear(auth);
    auth->initiated = 1;
    auth->protocol_version = 1;

    /* Import the given DH keypair, or else create a fresh one */
    if (our_dh) {
	otrl_dh_keypair_copy(&(auth->our_dh), our_dh);
	auth->our_keyid = our_keyid;
    } else {
	otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh));
	auth->our_keyid = 1;
    }

    err = create_v1_key_exchange_message(auth, 0, privkey);
    if (!err) {
	auth->authstate = OTRL_AUTHSTATE_V1_SETUP;
    }

    return err;
}

/*
 * Handle an incoming v1 Key Exchange Message.  If no error is returned,
 * and *havemsgp is 1, the message to be sent will be left in
 * auth->lastauthmsg.  Use the given private authentication key to sign
 * messages.  Call the auth_secceeded callback if authentication is
 * successful.  If non-NULL, use a copy of the given D-H keypair, with
 * the given keyid.
 */
gcry_error_t otrl_auth_handle_v1_key_exchange(OtrlAuthInfo *auth,
	const char *keyexchmsg, int *havemsgp, OtrlPrivKey *privkey,
	DH_keypair *our_dh, unsigned int our_keyid,
	gcry_error_t (*auth_succeeded)(const OtrlAuthInfo *auth, void *asdata),
	void *asdata)
{
    gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR);
    unsigned char *buf = NULL, *bufp = NULL;
    unsigned char *fingerprintstart, *fingerprintend;
    unsigned char fingerprintbuf[20], hashbuf[20];
    gcry_mpi_t p, q, g, y, received_pub = NULL;
    gcry_sexp_t pubs = NULL;
    size_t buflen, lenp;
    unsigned char received_reply;
    unsigned int received_keyid;
    int res;

    *havemsgp = 0;

    res = otrl_base64_otr_decode(keyexchmsg, &buf, &buflen);
    if (res == -1) goto memerr;
    if (res == -2) goto invval;

    bufp = buf;
    lenp = buflen;

    /* Header */
    require_len(3);
    if (memcmp(bufp, "\x00\x01\x0a", 3)) goto invval;
    bufp += 3; lenp -= 3;

    /* Reply */
    require_len(1);
    received_reply = bufp[0];
    bufp += 1; lenp -= 1;

    /* Public Key */
    fingerprintstart = bufp;
    read_mpi(p);
    read_mpi(q);
    read_mpi(g);
    read_mpi(y);
    fingerprintend = bufp;
    gcry_md_hash_buffer(GCRY_MD_SHA1, fingerprintbuf,
	    fingerprintstart, fingerprintend-fingerprintstart);
    gcry_sexp_build(&pubs, NULL,
	"(public-key (dsa (p %m)(q %m)(g %m)(y %m)))", p, q, g, y);
    gcry_mpi_release(p);
    gcry_mpi_release(q);
    gcry_mpi_release(g);
    gcry_mpi_release(y);

    /* keyid */
    read_int(received_keyid);
    if (received_keyid == 0) goto invval;

    /* D-H pubkey */
    read_mpi(received_pub);

    /* Verify the signature */
    if (lenp != 40) goto invval;
    gcry_md_hash_buffer(GCRY_MD_SHA1, hashbuf, buf, bufp - buf);
    err = otrl_privkey_verify(bufp, lenp, OTRL_PUBKEY_TYPE_DSA,
	    pubs, hashbuf, 20);
    if (err) goto err;
    gcry_sexp_release(pubs);
    pubs = NULL;
    free(buf);
    buf = NULL;

    if (auth->authstate != OTRL_AUTHSTATE_V1_SETUP && received_reply == 0x01) {
	/* They're replying to something we never sent.  We must be
	 * logged in more than once; ignore the message. */
	err = gpg_error(GPG_ERR_NO_ERROR);
	goto err;
    }

    if (auth->authstate != OTRL_AUTHSTATE_V1_SETUP) {
	/* Clear the auth and start over */
	otrl_auth_clear(auth);
    }

    /* Everything checked out */
    auth->their_keyid = received_keyid;
    gcry_mpi_release(auth->their_pub);
    auth->their_pub = received_pub;
    received_pub = NULL;
    memmove(auth->their_fingerprint, fingerprintbuf, 20);

    if (received_reply == 0x01) {
	/* Don't send a reply to this. */
	*havemsgp = 0;
    } else {
	/* Import the given DH keypair, or else create a fresh one */
	if (our_dh) {
	    otrl_dh_keypair_copy(&(auth->our_dh), our_dh);
	    auth->our_keyid = our_keyid;
	} else if (auth->our_keyid == 0) {
	    otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh));
	    auth->our_keyid = 1;
	}

	/* Reply with our own Key Exchange Message */
	err = create_v1_key_exchange_message(auth, 1, privkey);
	if (err) goto err;
	*havemsgp = 1;
    }

    /* Compute the session id */
    err = otrl_dh_compute_v1_session_id(&(auth->our_dh),
	    auth->their_pub, auth->secure_session_id,
	    &(auth->secure_session_id_len),
	    &(auth->session_id_half));
    if (err) goto err;

    /* We've completed our end of the authentication */
    auth->protocol_version = 1;
    if (auth_succeeded) err = auth_succeeded(auth, asdata);
    auth->our_keyid = 0;
    auth->authstate = OTRL_AUTHSTATE_NONE;

    return err;

invval:
    err = gcry_error(GPG_ERR_INV_VALUE);
    goto err;
memerr:
    err = gcry_error(GPG_ERR_ENOMEM);
err:
    free(buf);
    gcry_sexp_release(pubs);
    gcry_mpi_release(received_pub);
    return err;
}

/*
 * Copy relevant information from the master OtrlAuthInfo to an
 * instance OtrlAuthInfo in response to a D-H Key with a new
 * instance. The fields copied will depend on the state of the
 * master auth.
 */
void otrl_auth_copy_on_key(OtrlAuthInfo *m_auth, OtrlAuthInfo *auth)
{
    switch(m_auth->authstate) {
	case OTRL_AUTHSTATE_AWAITING_DHKEY:
	case OTRL_AUTHSTATE_AWAITING_SIG:
	    /* Copy our D-H Commit information to the new instance */
	    otrl_dh_keypair_free(&(auth->our_dh));
	    auth->initiated = m_auth->initiated;
	    otrl_dh_keypair_copy(&(auth->our_dh), &(m_auth->our_dh));
	    auth->our_keyid = m_auth->our_keyid;
	    memmove(auth->r, m_auth->r, 16);
	    if (auth->encgx) free(auth->encgx);
	    auth->encgx = malloc(m_auth->encgx_len);
	    memmove(auth->encgx, m_auth->encgx, m_auth->encgx_len);
	    memmove(auth->hashgx, m_auth->hashgx, 32);

	    auth->authstate = OTRL_AUTHSTATE_AWAITING_DHKEY;
	    break;

	default:
	    /* This bad state will be detected and handled later */
	    break;
    }
}

#ifdef OTRL_TESTING_AUTH
#include "mem.h"
#include "privkey.h"

#define CHECK_ERR if (err) { printf("Error: %s\n", gcry_strerror(err)); \
			return 1; }

static gcry_error_t starting(const OtrlAuthInfo *auth, void *asdata)
{
    char *name = asdata;

    fprintf(stderr, "\nStarting ENCRYPTED mode for %s (v%d).\n",
	    name, auth->protocol_version);

    fprintf(stderr, "\nour_dh (%d):", auth->our_keyid);
    gcry_mpi_dump(auth->our_dh.pub);
    fprintf(stderr, "\ntheir_pub (%d):", auth->their_keyid);
    gcry_mpi_dump(auth->their_pub);

    debug_data("\nTheir fingerprint", auth->their_fingerprint, 20);
    debug_data("\nSecure session id", auth->secure_session_id,
	    auth->secure_session_id_len);
    fprintf(stderr, "Sessionid half: %d\n\n", auth->session_id_half);

    return gpg_error(GPG_ERR_NO_ERROR);
}

int main(int argc, char **argv)
{
    OtrlAuthInfo alice, bob;
    gcry_error_t err;
    int havemsg;
    OtrlUserState us;
    OtrlPrivKey *alicepriv, *bobpriv;

    otrl_mem_init();
    otrl_dh_init();
    otrl_auth_new(&alice);
    otrl_auth_new(&bob);

    us = otrl_userstate_create();
    otrl_privkey_read(us, "/home/iang/.gaim/otr.private_key");
    alicepriv = otrl_privkey_find(us, "oneeyedian", "prpl-oscar");
    bobpriv = otrl_privkey_find(us, "otr4ian", "prpl-oscar");

    printf("\n\n  ***** V2 *****\n\n");

    err = otrl_auth_start_v23(&bob, NULL, 0);
    CHECK_ERR
    printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg);
    err = otrl_auth_handle_commit(&alice, bob.lastauthmsg, NULL, 0);
    CHECK_ERR
    printf("\nAlice: %d\n%s\n\n", strlen(alice.lastauthmsg), alice.lastauthmsg);
    err = otrl_auth_handle_key(&bob, alice.lastauthmsg, &havemsg, bobpriv);
    CHECK_ERR
    if (havemsg) {
	printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg);
    } else {
	printf("\nIGNORE\n\n");
    }
    err = otrl_auth_handle_revealsig(&alice, bob.lastauthmsg, &havemsg,
	    alicepriv, starting, "Alice");
    CHECK_ERR
    if (havemsg) {
	printf("\nAlice: %d\n%s\n\n", strlen(alice.lastauthmsg),
		alice.lastauthmsg);
    } else {
	printf("\nIGNORE\n\n");
    }
    err = otrl_auth_handle_signature(&bob, alice.lastauthmsg, &havemsg,
	    starting, "Bob");
    CHECK_ERR

    printf("\n\n  ***** V1 *****\n\n");

    err = otrl_auth_start_v1(&bob, NULL, 0, bobpriv);
    CHECK_ERR
    printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg);
    err = otrl_auth_handle_v1_key_exchange(&alice, bob.lastauthmsg,
	    &havemsg, alicepriv, NULL, 0, starting, "Alice");
    CHECK_ERR
    if (havemsg) {
	printf("\nAlice: %d\n%s\n\n", strlen(alice.lastauthmsg),
		alice.lastauthmsg);
    } else {
	printf("\nIGNORE\n\n");
    }
    err = otrl_auth_handle_v1_key_exchange(&bob, alice.lastauthmsg,
	    &havemsg, bobpriv, NULL, 0, starting, "Bob");
    CHECK_ERR
    if (havemsg) {
	printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg);
    } else {
	printf("\nIGNORE\n\n");
    }

    otrl_userstate_free(us);
    otrl_auth_clear(&alice);
    otrl_auth_clear(&bob);
    return 0;
}
#endif
