ssh.c

putty

		(st->pktin->type == SSH1_SMSG_STDERR_DATA)) {
		do_blank = TRUE; blank_prefix = 0;
	    } else if (st->pktin->type == SSH1_MSG_CHANNEL_DATA) {
		do_blank = TRUE; blank_prefix = 4;
	    }
	    if (do_blank) {
		blank.offset = blank_prefix;
		blank.len = st->pktin->length;
		blank.type = PKTLOG_OMIT;
		nblanks = 1;
	    }
	}
	log_packet(ssh->logctx,
		   PKT_INCOMING, st->pktin->type,
		   ssh1_pkt_type(st->pktin->type),
		   st->pktin->body, st->pktin->length,
		   nblanks, &blank);
    }

    crFinish(st->pktin);
}

static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
{
    struct rdpkt2_state_tag *st = &ssh->rdpkt2_state;

    crBegin(ssh->ssh2_rdpkt_crstate);

    st->pktin = ssh_new_packet();

    st->pktin->type = 0;
    st->pktin->length = 0;
    if (ssh->sccipher)
	st->cipherblk = ssh->sccipher->blksize;
    else
	st->cipherblk = 8;
    if (st->cipherblk < 8)
	st->cipherblk = 8;

    st->pktin->data = snewn(st->cipherblk + APIEXTRA, unsigned char);

    /*
     * Acquire and decrypt the first block of the packet. This will
     * contain the length and padding details.
     */
    for (st->i = st->len = 0; st->i < st->cipherblk; st->i++) {
	while ((*datalen) == 0)
	    crReturn(NULL);
	st->pktin->data[st->i] = *(*data)++;
	(*datalen)--;
    }

    if (ssh->sccipher)
	ssh->sccipher->decrypt(ssh->sc_cipher_ctx,
			       st->pktin->data, st->cipherblk);

    /*
     * Now get the length and padding figures.
     */
    st->len = GET_32BIT(st->pktin->data);
    st->pad = st->pktin->data[4];

    /*
     * _Completely_ silly lengths should be stomped on before they
     * do us any more damage.
     */
    if (st->len < 0 || st->len > 35000 || st->pad < 4 ||
	st->len - st->pad < 1 || (st->len + 4) % st->cipherblk != 0) {
	bombout(("Incoming packet was garbled on decryption"));
	ssh_free_packet(st->pktin);
	crStop(NULL);
    }

    /*
     * This enables us to deduce the payload length.
     */
    st->payload = st->len - st->pad - 1;

    st->pktin->length = st->payload + 5;

    /*
     * So now we can work out the total packet length.
     */
    st->packetlen = st->len + 4;
    st->maclen = ssh->scmac ? ssh->scmac->len : 0;

    /*
     * Allocate memory for the rest of the packet.
     */
    st->pktin->maxlen = st->packetlen + st->maclen;
    st->pktin->data = sresize(st->pktin->data,
			      st->pktin->maxlen + APIEXTRA,
			      unsigned char);

    /*
     * Read and decrypt the remainder of the packet.
     */
    for (st->i = st->cipherblk; st->i < st->packetlen + st->maclen;
	 st->i++) {
	while ((*datalen) == 0)
	    crReturn(NULL);
	st->pktin->data[st->i] = *(*data)++;
	(*datalen)--;
    }
    /* Decrypt everything _except_ the MAC. */
    if (ssh->sccipher)
	ssh->sccipher->decrypt(ssh->sc_cipher_ctx,
			       st->pktin->data + st->cipherblk,
			       st->packetlen - st->cipherblk);

    st->pktin->encrypted_len = st->packetlen;

    /*
     * Check the MAC.
     */
    if (ssh->scmac
	&& !ssh->scmac->verify(ssh->sc_mac_ctx, st->pktin->data, st->len + 4,
			       st->incoming_sequence)) {
	bombout(("Incorrect MAC received on packet"));
	ssh_free_packet(st->pktin);
	crStop(NULL);
    }

    st->pktin->sequence = st->incoming_sequence++;

    /*
     * Decompress packet payload.
     */
    {
	unsigned char *newpayload;
	int newlen;
	if (ssh->sccomp &&
	    ssh->sccomp->decompress(ssh->sc_comp_ctx,
				    st->pktin->data + 5, st->pktin->length - 5,
				    &newpayload, &newlen)) {
	    if (st->pktin->maxlen < newlen + 5) {
		st->pktin->maxlen = newlen + 5;
		st->pktin->data = sresize(st->pktin->data,
					  st->pktin->maxlen + APIEXTRA,
					  unsigned char);
	    }
	    st->pktin->length = 5 + newlen;
	    memcpy(st->pktin->data + 5, newpayload, newlen);
	    sfree(newpayload);
	}
    }

    st->pktin->savedpos = 6;
    st->pktin->body = st->pktin->data;
    st->pktin->type = st->pktin->data[5];

    /*
     * Log incoming packet, possibly omitting sensitive fields.
     */
    if (ssh->logctx) {
	int nblanks = 0;
	struct logblank_t blank;
	if (ssh->cfg.logomitdata) {
	    int do_blank = FALSE, blank_prefix = 0;
	    /* "Session data" packets - omit the data field */
	    if (st->pktin->type == SSH2_MSG_CHANNEL_DATA) {
		do_blank = TRUE; blank_prefix = 4;
	    } else if (st->pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA) {
		do_blank = TRUE; blank_prefix = 8;
	    }
	    if (do_blank) {
		blank.offset = blank_prefix;
		blank.len = (st->pktin->length-6) - blank_prefix;
		blank.type = PKTLOG_OMIT;
		nblanks = 1;
	    }
	}
	log_packet(ssh->logctx, PKT_INCOMING, st->pktin->type,
		   ssh2_pkt_type(ssh->pkt_ctx, st->pktin->type),
		   st->pktin->data+6, st->pktin->length-6,
		   nblanks, &blank);
    }

    crFinish(st->pktin);
}

static int s_wrpkt_prepare(Ssh ssh, struct Packet *pkt, int *offset_p)
{
    int pad, biglen, i, pktoffs;
    unsigned long crc;
#ifdef __SC__
    /*
     * XXX various versions of SC (including 8.8.4) screw up the
     * register allocation in this function and use the same register
     * (D6) for len and as a temporary, with predictable results.  The
     * following sledgehammer prevents this.
     */
    volatile
#endif
    int len;

    if (ssh->logctx)
	log_packet(ssh->logctx, PKT_OUTGOING, pkt->data[12],
		   ssh1_pkt_type(pkt->data[12]),
		   pkt->body, pkt->length - (pkt->body - pkt->data),
		   pkt->nblanks, pkt->blanks);
    sfree(pkt->blanks); pkt->blanks = NULL;
    pkt->nblanks = 0;

    if (ssh->v1_compressing) {
	unsigned char *compblk;
	int complen;
	zlib_compress_block(ssh->cs_comp_ctx,
			    pkt->data + 12, pkt->length - 12,
			    &compblk, &complen);
	memcpy(pkt->data + 12, compblk, complen);
	sfree(compblk);
	pkt->length = complen + 12;
    }

    ssh_pkt_ensure(pkt, pkt->length + 4); /* space for CRC */
    pkt->length += 4;
    len = pkt->length - 4 - 8;	/* len(type+data+CRC) */
    pad = 8 - (len % 8);
    pktoffs = 8 - pad;
    biglen = len + pad;		/* len(padding+type+data+CRC) */

    for (i = pktoffs; i < 4+8; i++)
	pkt->data[i] = random_byte();
    crc = crc32_compute(pkt->data + pktoffs + 4, biglen - 4); /* all ex len */
    PUT_32BIT(pkt->data + pktoffs + 4 + biglen - 4, crc);
    PUT_32BIT(pkt->data + pktoffs, len);

    if (ssh->cipher)
	ssh->cipher->encrypt(ssh->v1_cipher_ctx,
			     pkt->data + pktoffs + 4, biglen);

    if (offset_p) *offset_p = pktoffs;
    return biglen + 4;		/* len(length+padding+type+data+CRC) */
}

static int s_write(Ssh ssh, void *data, int len)
{
    log_packet(ssh->logctx, PKT_OUTGOING, -1, NULL, data, len, 0, NULL);
    return sk_write(ssh->s, (char *)data, len);
}

static void s_wrpkt(Ssh ssh, struct Packet *pkt)
{
    int len, backlog, offset;
    len = s_wrpkt_prepare(ssh, pkt, &offset);
    backlog = s_write(ssh, pkt->data + offset, len);
    if (backlog > SSH_MAX_BACKLOG)
	ssh_throttle_all(ssh, 1, backlog);
    ssh_free_packet(pkt);
}

static void s_wrpkt_defer(Ssh ssh, struct Packet *pkt)
{
    int len, offset;
    len = s_wrpkt_prepare(ssh, pkt, &offset);
    if (ssh->deferred_len + len > ssh->deferred_size) {
	ssh->deferred_size = ssh->deferred_len + len + 128;
	ssh->deferred_send_data = sresize(ssh->deferred_send_data,
					  ssh->deferred_size,
					  unsigned char);
    }
    memcpy(ssh->deferred_send_data + ssh->deferred_len,
	   pkt->data + offset, len);
    ssh->deferred_len += len;
    ssh_free_packet(pkt);
}

/*
 * Construct a SSH-1 packet with the specified contents.
 * (This all-at-once interface used to be the only one, but now SSH-1
 * packets can also be constructed incrementally.)
 */
static struct Packet *construct_packet(Ssh ssh, int pkttype, va_list ap)
{
    int argtype;
    Bignum bn;
    struct Packet *pkt;

    pkt = ssh1_pkt_init(pkttype);

    while ((argtype = va_arg(ap, int)) != PKT_END) {
	unsigned char *argp, argchar;
	char *sargp;
	unsigned long argint;
	int arglen;
	switch (argtype) {
	  /* Actual fields in the packet */
	  case PKT_INT:
	    argint = va_arg(ap, int);
	    ssh_pkt_adduint32(pkt, argint);
	    break;
	  case PKT_CHAR:
	    argchar = (unsigned char) va_arg(ap, int);
	    ssh_pkt_addbyte(pkt, argchar);
	    break;
	  case PKT_DATA:
	    argp = va_arg(ap, unsigned char *);
	    arglen = va_arg(ap, int);
	    ssh_pkt_adddata(pkt, argp, arglen);
	    break;
	  case PKT_STR:
	    sargp = va_arg(ap, char *);
	    ssh_pkt_addstring(pkt, sargp);
	    break;
	  case PKT_BIGNUM:
	    bn = va_arg(ap, Bignum);
	    ssh1_pkt_addmp(pkt, bn);
	    break;
	  /* Tokens for modifications to packet logging */
	  case PKTT_PASSWORD:
	    dont_log_password(ssh, pkt, PKTLOG_BLANK);
	    break;
	  case PKTT_DATA:
	    dont_log_data(ssh, pkt, PKTLOG_OMIT);
	    break;
	  case PKTT_OTHER:
	    end_log_omission(ssh, pkt);
	    break;
	}
    }

    return pkt;
}

static void send_packet(Ssh ssh, int pkttype, ...)
{
    struct Packet *pkt;
    va_list ap;
    va_start(ap, pkttype);
    pkt = construct_packet(ssh, pkttype, ap);
    va_end(ap);
    s_wrpkt(ssh, pkt);
}

static void defer_packet(Ssh ssh, int pkttype, ...)
{
    struct Packet *pkt;
    va_list ap;
    va_start(ap, pkttype);
    pkt = construct_packet(ssh, pkttype, ap);
    va_end(ap);
    s_wrpkt_defer(ssh, pkt);
}

static int ssh_versioncmp(char *a, char *b)
{
    char *ae, *be;
    unsigned long av, bv;

    av = strtoul(a, &ae, 10);
    bv = strtoul(b, &be, 10);
    if (av != bv)
	return (av < bv ? -1 : +1);
    if (*ae == '.')
	ae++;
    if (*be == '.')
	be++;
    av = strtoul(ae, &ae, 10);
    bv = strtoul(be, &be, 10);
    if (av != bv)
	return (av < bv ? -1 : +1);
    return 0;
}

/*
 * Utility routines for putting an SSH-protocol `string' and
 * `uint32' into a hash state.
 */
static void hash_string(const struct ssh_hash *h, void *s, void *str, int len)
{
    unsigned char lenblk[4];
    PUT_32BIT(lenblk, len);
    h->bytes(s, lenblk, 4);
    h->bytes(s, str, len);
}

static void hash_uint32(const struct ssh_hash *h, void *s, unsigned i)
{
    unsigned char intblk[4];
    PUT_32BIT(intblk, i);
    h->bytes(s, intblk, 4);
}

/*
 * Packet construction functions. Mostly shared between SSH-1 and SSH-2.
 */
static void ssh_pkt_ensure(struct Packet *pkt, int length)
{
    if (pkt->maxlen < length) {
	unsigned char *body = pkt->body;
	int offset = body ? body - pkt->data : 0;
	pkt->maxlen = length + 256;
	pkt->data = sresize(pkt->data, pkt->maxlen + APIEXTRA, unsigned char);
	if (body) pkt->body = pkt->data + offset;
    }
}
static void ssh_pkt_adddata(struct Packet *pkt, void *data, int len)
{
    if (pkt->logmode != PKTLOG_EMIT) {
	pkt->nblanks++;
	pkt->blanks = sresize(pkt->blanks, pkt->nblanks, struct logblank_t);
	assert(pkt->body);