/*
 * Gather (Read) entire SSL2 records from socket into buffer.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "cert.h"
#include "ssl.h"
#include "sslimpl.h"
#include "sslproto.h"

/* Forward static declarations */
static SECStatus ssl2_HandleV3HandshakeRecord(sslSocket *ss);

/*
** Gather a single record of data from the receiving stream. This code
** first gathers the header (2 or 3 bytes long depending on the value of
** the most significant bit in the first byte) then gathers up the data
** for the record into gs->buf. This code handles non-blocking I/O
** and is to be called multiple times until ss->sec.recordLen != 0.
** This function decrypts the gathered record in place, in gs_buf.
 *
 * Caller must hold RecvBufLock.
 *
 * Returns +1 when it has gathered a complete SSLV2 record.
 * Returns  0 if it hits EOF.
 * Returns -1 (SECFailure)    on any error
 * Returns -2 (SECWouldBlock) when it gathers an SSL v3 client hello header.
**
** The SSL2 Gather State machine has 4 states:
** GS_INIT   - Done reading in previous record.  Haven't begun to read in
**             next record.  When ssl2_GatherData is called with the machine
**             in this state, the machine will attempt to read the first 3
**             bytes of the SSL2 record header, and will advance the state
**             to GS_HEADER.
**
** GS_HEADER - The machine is in this state while waiting for the completion
**             of the first 3 bytes of the SSL2 record.  When complete, the
**             machine will compute the remaining unread length of this record
**             and will initiate a read of that many bytes.  The machine will
**             advance to one of two states, depending on whether the record
**             is encrypted (GS_MAC), or unencrypted (GS_DATA).
**
** GS_MAC    - The machine is in this state while waiting for the remainder
**             of the SSL2 record to be read in.  When the read is completed,
**             the machine checks the record for valid length, decrypts it,
**             and checks and discards the MAC, then advances to GS_INIT.
**
** GS_DATA   - The machine is in this state while waiting for the remainder
**             of the unencrypted SSL2 record to be read in.  Upon completion,
**             the machine advances to the GS_INIT state and returns the data.
*/
int
ssl2_GatherData(sslSocket *ss, sslGather *gs, int flags)
{
    unsigned char *bp;
    unsigned char *pBuf;
    int nb, err, rv;

    PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));

    if (gs->state == GS_INIT) {
        /* Initialize gathering engine */
        gs->state = GS_HEADER;
        gs->remainder = 3;
        gs->count = 3;
        gs->offset = 0;
        gs->recordLen = 0;
        gs->recordPadding = 0;
        gs->hdr[2] = 0;

        gs->writeOffset = 0;
        gs->readOffset = 0;
    }
    if (gs->encrypted) {
        PORT_Assert(ss->sec.hash != 0);
    }

    pBuf = gs->buf.buf;
    for (;;) {
        SSL_TRC(30, ("%d: SSL[%d]: gather state %d (need %d more)",
                     SSL_GETPID(), ss->fd, gs->state, gs->remainder));
        bp = ((gs->state != GS_HEADER) ? pBuf : gs->hdr) + gs->offset;
        nb = ssl_DefRecv(ss, bp, gs->remainder, flags);
        if (nb > 0) {
            PRINT_BUF(60, (ss, "raw gather data:", bp, nb));
        }
        if (nb == 0) {
            /* EOF */
            SSL_TRC(30, ("%d: SSL[%d]: EOF", SSL_GETPID(), ss->fd));
            rv = 0;
            break;
        }
        if (nb < 0) {
            SSL_DBG(("%d: SSL[%d]: recv error %d", SSL_GETPID(), ss->fd,
                     PR_GetError()));
            rv = SECFailure;
            break;
        }

        gs->offset += nb;
        gs->remainder -= nb;

        if (gs->remainder > 0) {
            continue;
        }

        /* Probably finished this piece */
        switch (gs->state) {
            case GS_HEADER:
                if (!SSL3_ALL_VERSIONS_DISABLED(&ss->vrange) && !ss->firstHsDone) {

                    PORT_Assert(ss->opt.noLocks || ssl_Have1stHandshakeLock(ss));

                    /* If this looks like an SSL3 handshake record,
                    ** and we're expecting an SSL2 Hello message from our peer,
                    ** handle it here.
                    */
                    if (gs->hdr[0] == content_handshake) {
                        if ((ss->nextHandshake == ssl2_HandleClientHelloMessage) ||
                            (ss->nextHandshake == ssl2_HandleServerHelloMessage)) {
                            rv = ssl2_HandleV3HandshakeRecord(ss);
                            if (rv == SECFailure) {
                                return SECFailure;
                            }
                        }
                        /* XXX_1    The call stack to here is:
                         * ssl_Do1stHandshake -> ssl_GatherRecord1stHandshake ->
                         *          ssl2_GatherRecord -> here.
                         * We want to return all the way out to ssl_Do1stHandshake,
                         * and have it call ssl_GatherRecord1stHandshake again.
                         * ssl_GatherRecord1stHandshake will call
                         * ssl3_GatherCompleteHandshake when it is called again.
                         *
                         * Returning SECWouldBlock here causes
                         * ssl_GatherRecord1stHandshake to return without clearing
                         * ss->handshake, ensuring that ssl_Do1stHandshake will
                         * call it again immediately.
                         *
                         * If we return 1 here, ssl_GatherRecord1stHandshake will
                         * clear ss->handshake before returning, and thus will not
                         * be called again by ssl_Do1stHandshake.
                         */
                        return SECWouldBlock;
                    } else if (gs->hdr[0] == content_alert) {
                        if (ss->nextHandshake == ssl2_HandleServerHelloMessage) {
                            /* XXX This is a hack.  We're assuming that any failure
                             * XXX on the client hello is a failure to match
                             * XXX ciphers.
                             */
                            PORT_SetError(SSL_ERROR_NO_CYPHER_OVERLAP);
                            return SECFailure;
                        }
                    }
                }

                /* we've got the first 3 bytes.  The header may be two or three. */
                if (gs->hdr[0] & 0x80) {
                    /* This record has a 2-byte header, and no padding */
                    gs->count = ((gs->hdr[0] & 0x7f) << 8) | gs->hdr[1];
                    gs->recordPadding = 0;
                } else {
                    /* This record has a 3-byte header that is all read in now. */
                    gs->count = ((gs->hdr[0] & 0x3f) << 8) | gs->hdr[1];
                    /*  is_escape =  (gs->hdr[0] & 0x40) != 0; */
                    gs->recordPadding = gs->hdr[2];
                }
                if (!gs->count) {
                    PORT_SetError(SSL_ERROR_RX_RECORD_TOO_LONG);
                    goto cleanup;
                }

                if (gs->count > gs->buf.space) {
                    err = sslBuffer_Grow(&gs->buf, gs->count);
                    if (err) {
                        return err;
                    }
                    pBuf = gs->buf.buf;
                }

                if (gs->hdr[0] & 0x80) {
                    /* we've already read in the first byte of the body.
                    ** Put it into the buffer.
                    */
                    pBuf[0] = gs->hdr[2];
                    gs->offset = 1;
                    gs->remainder = gs->count - 1;
                } else {
                    gs->offset = 0;
                    gs->remainder = gs->count;
                }

                if (gs->encrypted) {
                    gs->state = GS_MAC;
                    gs->recordLen = gs->count - gs->recordPadding -
                                    ss->sec.hash->length;
                } else {
                    gs->state = GS_DATA;
                    gs->recordLen = gs->count;
                }

                break;

            case GS_MAC:
                /* Have read in entire rest of the ciphertext.
                ** Check for valid length.
                ** Decrypt it.
                ** Check the MAC.
                */
                PORT_Assert(gs->encrypted);

                {
                    unsigned int macLen;
                    int nout;
                    unsigned char mac[SSL_MAX_MAC_BYTES];

                    ssl_GetSpecReadLock(ss); /**********************************/

                    /* If this is a stream cipher, blockSize will be 1,
                     * and this test will always be false.
                     * If this is a block cipher, this will detect records
                     * that are not a multiple of the blocksize in length.
                     */
                    if (gs->count & (ss->sec.blockSize - 1)) {
                        /* This is an error. Sender is misbehaving */
                        SSL_DBG(("%d: SSL[%d]: sender, count=%d blockSize=%d",
                                 SSL_GETPID(), ss->fd, gs->count,
                                 ss->sec.blockSize));
                        PORT_SetError(SSL_ERROR_BAD_BLOCK_PADDING);
                        rv = SECFailure;
                        goto spec_locked_done;
                    }
                    PORT_Assert(gs->count == gs->offset);

                    if (gs->offset == 0) {
                        rv = 0; /* means EOF. */
                        goto spec_locked_done;
                    }

                    /* Decrypt the portion of data that we just received.
                    ** Decrypt it in place.
                    */
                    rv = (*ss->sec.dec)(ss->sec.readcx, pBuf, &nout, gs->offset,
                                        pBuf, gs->offset);
                    if (rv != SECSuccess) {
                        goto spec_locked_done;
                    }

                    /* Have read in all the MAC portion of record
                    **
                    ** Prepare MAC by resetting it and feeding it the shared secret
                    */
                    macLen = ss->sec.hash->length;
                    if (gs->offset >= macLen) {
                        PRUint32 sequenceNumber = ss->sec.rcvSequence++;
                        unsigned char seq[4];

                        seq[0] = (unsigned char)(sequenceNumber >> 24);
                        seq[1] = (unsigned char)(sequenceNumber >> 16);
                        seq[2] = (unsigned char)(sequenceNumber >> 8);
                        seq[3] = (unsigned char)(sequenceNumber);

                        (*ss->sec.hash->begin)(ss->sec.hashcx);
                        (*ss->sec.hash->update)(ss->sec.hashcx, ss->sec.rcvSecret.data,
                                                ss->sec.rcvSecret.len);
                        (*ss->sec.hash->update)(ss->sec.hashcx, pBuf + macLen,
                                                gs->offset - macLen);
                        (*ss->sec.hash->update)(ss->sec.hashcx, seq, 4);
                        (*ss->sec.hash->end)(ss->sec.hashcx, mac, &macLen, macLen);

                        PORT_Assert(macLen == ss->sec.hash->length);

                        ssl_ReleaseSpecReadLock(ss); /******************************/

                        if (NSS_SecureMemcmp(mac, pBuf, macLen) != 0) {
                            /* MAC's didn't match... */
                            SSL_DBG(("%d: SSL[%d]: mac check failed, seq=%d",
                                     SSL_GETPID(), ss->fd, ss->sec.rcvSequence));
                            PRINT_BUF(1, (ss, "computed mac:", mac, macLen));
                            PRINT_BUF(1, (ss, "received mac:", pBuf, macLen));
                            PORT_SetError(SSL_ERROR_BAD_MAC_READ);
                            rv = SECFailure;
                            goto cleanup;
                        }
                    } else {
                        ssl_ReleaseSpecReadLock(ss); /******************************/
                    }

                    if (gs->recordPadding + macLen <= gs->offset) {
                        gs->recordOffset = macLen;
                        gs->readOffset = macLen;
                        gs->writeOffset = gs->offset - gs->recordPadding;
                        rv = 1;
                    } else {
                        PORT_SetError(SSL_ERROR_BAD_BLOCK_PADDING);
                    cleanup:
                        /* nothing in the buffer any more. */
                        gs->recordOffset = 0;
                        gs->readOffset = 0;
                        gs->writeOffset = 0;
                        rv = SECFailure;
                    }

                    gs->recordLen = gs->writeOffset - gs->readOffset;
                    gs->recordPadding = 0; /* forget we did any padding. */
                    gs->state = GS_INIT;

                    if (rv > 0) {
                        PRINT_BUF(50, (ss, "recv clear record:",
                                       pBuf + gs->recordOffset, gs->recordLen));
                    }
                    return rv;

                spec_locked_done:
                    ssl_ReleaseSpecReadLock(ss);
                    return rv;
                }

            case GS_DATA:
                /* Have read in all the DATA portion of record */

                gs->recordOffset = 0;
                gs->readOffset = 0;
                gs->writeOffset = gs->offset;
                PORT_Assert(gs->recordLen == gs->writeOffset - gs->readOffset);
                gs->recordLen = gs->offset;
                gs->recordPadding = 0;
                gs->state = GS_INIT;

                ++ss->sec.rcvSequence;

                PRINT_BUF(50, (ss, "recv clear record:",
                               pBuf + gs->recordOffset, gs->recordLen));
                return 1;

        } /* end switch gs->state */
    }     /* end gather loop. */
    return rv;
}

/*
** Gather a single record of data from the receiving stream. This code
** first gathers the header (2 or 3 bytes long depending on the value of
** the most significant bit in the first byte) then gathers up the data
** for the record into the readBuf. This code handles non-blocking I/O
** and is to be called multiple times until ss->sec.recordLen != 0.
 *
 * Returns +1 when it has gathered a complete SSLV2 record.
 * Returns  0 if it hits EOF.
 * Returns -1 (SECFailure)    on any error
 * Returns -2 (SECWouldBlock)
 *
 * Called by ssl_GatherRecord1stHandshake in sslcon.c,
 * and by DoRecv in sslsecur.c
 * Caller must hold RecvBufLock.
 */
int
ssl2_GatherRecord(sslSocket *ss, int flags)
{
    return ssl2_GatherData(ss, &ss->gs, flags);
}

/* Caller should hold RecvBufLock. */
SECStatus
ssl_InitGather(sslGather *gs)
{
    SECStatus status;

    gs->state = GS_INIT;
    gs->writeOffset = 0;
    gs->readOffset = 0;
    gs->dtlsPacketOffset = 0;
    gs->dtlsPacket.len = 0;
    status = sslBuffer_Grow(&gs->buf, 4096);
    return status;
}

/* Caller must hold RecvBufLock. */
void
ssl_DestroyGather(sslGather *gs)
{
    if (gs) { /* the PORT_*Free functions check for NULL pointers. */
        PORT_ZFree(gs->buf.buf, gs->buf.space);
        PORT_Free(gs->inbuf.buf);
        PORT_Free(gs->dtlsPacket.buf);
    }
}

/* Caller must hold RecvBufLock. */
static SECStatus
ssl2_HandleV3HandshakeRecord(sslSocket *ss)
{
    SECStatus rv;

    PORT_Assert(ss->opt.noLocks || ssl_HaveRecvBufLock(ss));
    PORT_Assert(ss->opt.noLocks || ssl_Have1stHandshakeLock(ss));

    /* We've read in 3 bytes, there are 2 more to go in an ssl3 header. */
    ss->gs.remainder = 2;
    ss->gs.count = 0;

    /* Clearing these handshake pointers ensures that
     * ssl_Do1stHandshake won't call ssl2_HandleMessage when we return.
     */
    ss->nextHandshake = 0;
    ss->securityHandshake = 0;

    /* Setting ss->version to an SSL 3.x value will cause
    ** ssl_GatherRecord1stHandshake to invoke ssl3_GatherCompleteHandshake()
    ** the next time it is called.
    **/
    rv = ssl3_NegotiateVersion(ss, SSL_LIBRARY_VERSION_MAX_SUPPORTED,
                               PR_TRUE);
    if (rv != SECSuccess) {
        return rv;
    }

    ss->sec.send = ssl3_SendApplicationData;

    return SECSuccess;
}
