/* 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/.

 *

 *    Copyright 2014-2020 (c) Fraunhofer IOSB (Author: Julius Pfrommer)

 *    Copyright 2014, 2016-2017 (c) Florian Palm

 *    Copyright 2015-2016 (c) Sten Grüner

 *    Copyright 2015 (c) Oleksiy Vasylyev

 *    Copyright 2016 (c) TorbenD

 *    Copyright 2017 (c) Stefan Profanter, fortiss GmbH

 *    Copyright 2017-2018 (c) Mark Giraud, Fraunhofer IOSB

 *    Copyright 2018-2019 (c) HMS Industrial Networks AB (Author: Jonas Green)

 *    Copyright 2025 (c) o6 Automation GmbH (Author: Julius Pfrommer)

 *    Copyright 2026 (c) o6 Automation GmbH (Author: Andreas Ebner)

 */

#include <open62541/types.h>

#include <open62541/transport_generated.h>

#include "ua_securechannel.h"

#include "ua_types_encoding_binary.h"

#define UA_BITMASK_MESSAGETYPE 0x00ffffffu

#define UA_BITMASK_CHUNKTYPE 0xff000000u

const UA_String UA_SECURITY_POLICY_NONE_URI =

    {47, (UA_Byte *)"http://opcfoundation.org/UA/SecurityPolicy#None"};

void

UA_SecureChannel_init(UA_SecureChannel *channel) {

    /* Normal linked lists are initialized by zeroing out */

    memset(channel, 0, sizeof(UA_SecureChannel));

    TAILQ_INIT(&channel->chunks);

}

UA_StatusCode

UA_SecureChannel_setSecurityPolicy(UA_SecureChannel *channel, UA_SecurityPolicy *sp,

                                   const UA_ByteString *remoteCertificate) {

    /* Is a policy already configured? */

    UA_CHECK_ERROR(!channel->securityPolicy, return UA_STATUSCODE_BADINTERNALERROR,

                   sp->logger, UA_LOGCATEGORY_SECURITYPOLICY,

                   "Security policy already configured");

    /* Create the context */

    UA_StatusCode res = sp->newChannelContext(sp, remoteCertificate,

                                              &channel->channelContext);

    res |= UA_ByteString_copy(remoteCertificate, &channel->remoteCertificate);

    UA_CHECK_STATUS_ERROR(res, return res, sp->logger, UA_LOGCATEGORY_SECURITYPOLICY,

                          "Could not set up the SecureChannel context");

    /* Compute the certificate thumbprint */

    UA_ByteString remoteCertificateThumbprint =

        {20, channel->remoteCertificateThumbprint};

    res = sp->makeCertThumbprint(sp, &channel->remoteCertificate,

                                 &remoteCertificateThumbprint);

    UA_CHECK_STATUS_ERROR(res, return res, sp->logger, UA_LOGCATEGORY_SECURITYPOLICY,

                          "Could not create the certificate thumbprint");

    /* Set the SecurityPolicy and cache the URI-derived properties (the policy

     * is fixed for the channel's lifetime). */

    channel->securityPolicy = sp;

    channel->enhancedSecurity = UA_SecurityPolicy_isEnhancedSecurity(sp);

    channel->legacySequenceNumbers = UA_SecurityPolicy_useLegacySequenceNumbers(sp);

    /* Set a temporary SecurityMode. The client sets the final SecurityMode

     * right after. The server only after fully decoding the OPN message in the

     * OpenSecureChannel service. But we need the SecurityMode for decoding. The

     * OPN message is always signed and encrypted when not #None. */

    if(sp->policyType == UA_SECURITYPOLICYTYPE_NONE)

        channel->securityMode = UA_MESSAGESECURITYMODE_NONE;

    else

        channel->securityMode = UA_MESSAGESECURITYMODE_SIGNANDENCRYPT;

    return UA_STATUSCODE_GOOD;

}

/* The #None SecurityPolicy must use the NONE SecurityMode. All other

 * SecurityPolicies must not. */

UA_StatusCode

UA_SecureChannel_setSecurityMode(UA_SecureChannel *channel,

                                 UA_MessageSecurityMode securityMode) {

    if(securityMode == UA_MESSAGESECURITYMODE_INVALID ||

       securityMode > UA_MESSAGESECURITYMODE_SIGNANDENCRYPT)

        return UA_STATUSCODE_BADSECURITYMODEREJECTED;

    UA_SecurityPolicy *sp = channel->securityPolicy;

    if(!sp)

        return UA_STATUSCODE_BADSECURITYMODEREJECTED;

    UA_Boolean isNonePolicy = (sp->policyType == UA_SECURITYPOLICYTYPE_NONE);

    UA_Boolean isNoneMode = (securityMode == UA_MESSAGESECURITYMODE_NONE);

    if(isNonePolicy != isNoneMode)

        return UA_STATUSCODE_BADSECURITYMODEREJECTED;

    channel->securityMode = securityMode;

    return UA_STATUSCODE_GOOD;

}

/* Hides some errors before sending them to a client according to the

 * standard. */

static void

hideErrors(UA_TcpErrorMessage *const error) {

    switch(error->error) {

    case UA_STATUSCODE_BADCERTIFICATEINVALID:

    case UA_STATUSCODE_BADCERTIFICATECHAININCOMPLETE:

    case UA_STATUSCODE_BADCERTIFICATEPOLICYCHECKFAILED:

    case UA_STATUSCODE_BADCERTIFICATEUNTRUSTED:

    case UA_STATUSCODE_BADCERTIFICATEREVOCATIONUNKNOWN:

    case UA_STATUSCODE_BADCERTIFICATEISSUERREVOCATIONUNKNOWN:

    case UA_STATUSCODE_BADCERTIFICATEREVOKED:

    case UA_STATUSCODE_BADCERTIFICATEISSUERREVOKED:

    case UA_STATUSCODE_BADCERTIFICATEISSUERUSENOTALLOWED:

        error->error = UA_STATUSCODE_BADSECURITYCHECKSFAILED;

        error->reason = UA_STRING_NULL;

        break;

        // TODO: Check if these are all cases that need to be covered.

    default:

        break;

    }

}

UA_Boolean

UA_SecureChannel_isConnected(UA_SecureChannel *channel) {

    return (channel->state > UA_SECURECHANNELSTATE_CLOSED &&

            channel->state < UA_SECURECHANNELSTATE_CLOSING);

}

void

UA_SecureChannel_sendERR(UA_SecureChannel *channel, UA_TcpErrorMessage *error) {

    if(!UA_SecureChannel_isConnected(channel))

        return;

    hideErrors(error);

    UA_TcpMessageHeader header;

    header.messageTypeAndChunkType = UA_MESSAGETYPE_ERR + UA_CHUNKTYPE_FINAL;

    /* Header + ErrorMessage (error + reasonLength_field + length) */

    header.messageSize = 8 + (4 + 4 + (UA_UInt32)error->reason.length);

    /* Get the send buffer from the network layer */

    UA_ConnectionManager *cm = channel->connectionManager;

    UA_ByteString msg = UA_BYTESTRING_NULL;

    UA_StatusCode retval = cm->allocNetworkBuffer(cm, channel->connectionId,

                                                  &msg, header.messageSize);

    if(retval != UA_STATUSCODE_GOOD)

        return;

    /* Encode and send the response */

    UA_Byte *bufPos = msg.data;

    const UA_Byte *bufEnd = &msg.data[msg.length];

    retval |= UA_encodeBinaryInternal(&header,

                                      &UA_TRANSPORT[UA_TRANSPORT_TCPMESSAGEHEADER],

                                      &bufPos, &bufEnd, NULL, NULL, NULL);

    retval |= UA_encodeBinaryInternal(error,

                                      &UA_TRANSPORT[UA_TRANSPORT_TCPERRORMESSAGE],

                                      &bufPos, &bufEnd, NULL, NULL, NULL);

    (void)retval; /* Encoding of these cannot fail */

    msg.length = header.messageSize;

    cm->sendWithConnection(cm, channel->connectionId, &UA_KEYVALUEMAP_NULL, &msg);

}

static void

UA_Chunk_delete(UA_Chunk *chunk) {

    if(chunk->copied)

        UA_ByteString_clear(&chunk->bytes);

    UA_free(chunk);

}

static void

deleteChunks(UA_SecureChannel *channel) {

    UA_Chunk *chunk, *chunk_tmp;

    TAILQ_FOREACH_SAFE(chunk, &channel->chunks, pointers, chunk_tmp) {

        TAILQ_REMOVE(&channel->chunks, chunk, pointers);

        UA_Chunk_delete(chunk);

    }

    channel->chunksCount = 0;

    channel->chunksLength = 0;

}

void

UA_SecureChannel_deleteBuffered(UA_SecureChannel *channel) {

    deleteChunks(channel);

    if(channel->unprocessedCopied)

        UA_ByteString_clear(&channel->unprocessed);

}

void

UA_SecureChannel_shutdown(UA_SecureChannel *channel,

                          UA_ShutdownReason shutdownReason) {

    /* No open socket or already closing -> nothing to do */

    if(!UA_SecureChannel_isConnected(channel))

        return;

    /* Set the shutdown event for diagnostics */

    channel->shutdownReason = shutdownReason;

    /* Trigger the async closing of the connection */

    UA_ConnectionManager *cm = channel->connectionManager;

    cm->closeConnection(cm, channel->connectionId);

    channel->state = UA_SECURECHANNELSTATE_CLOSING;

}

void

UA_SecureChannel_clear(UA_SecureChannel *channel) {

    /* No sessions must be attached to this any longer */

    UA_assert(channel->sessions == NULL);

    /* Delete the channel context for the security policy */

    UA_SecurityPolicy *sp = channel->securityPolicy;

    if(sp) {

        sp->deleteChannelContext(sp, channel->channelContext);

        channel->securityPolicy = NULL;

        channel->channelContext = NULL;

        channel->enhancedSecurity = false;     /* No policy => not enhanced */

        channel->legacySequenceNumbers = true; /* No policy => legacy */

    }

    /* Remove remaining delayed callback */

    if(channel->connectionManager &&

       channel->connectionManager->eventSource.eventLoop) {

        UA_EventLoop *el = channel->connectionManager->eventSource.eventLoop;

        el->removeDelayedCallback(el, &channel->unprocessedDelayed);

    }

    /* The EventLoop connection is no longer valid */

    channel->connectionId = 0;

    channel->connectionManager = NULL;

    /* Clean up the SecurityToken */

    UA_ChannelSecurityToken_clear(&channel->securityToken);

    UA_ChannelSecurityToken_clear(&channel->altSecurityToken);

    /* Clean up certificate and nonces */

    UA_ByteString_clear(&channel->remoteCertificate);

    UA_ByteString_clear(&channel->localNonce);

    UA_ByteString_clear(&channel->remoteNonce);

    /* Clean up the v1.05.07 SecureChannel elements */

    UA_ByteString_clear(&channel->firstRequestSignature);

    UA_ByteString_clear(&channel->currentIKM);

    UA_ByteString_clear(&channel->channelThumbprint);

    /* Clean up endpointUrl and remoteAddress */

    UA_String_clear(&channel->endpointUrl);

    UA_String_clear(&channel->remoteAddress);

    /* Delete remaining chunks */

    UA_SecureChannel_deleteBuffered(channel);

    /* Clean up namespace mapping */

    UA_NamespaceMapping_delete(channel->namespaceMapping);

    channel->namespaceMapping = NULL;

    /* Reset the SecureChannel for reuse (in the client) */

    channel->securityMode = UA_MESSAGESECURITYMODE_INVALID;

    channel->shutdownReason = UA_SHUTDOWNREASON_CLOSE;

    memset(&channel->config, 0, sizeof(UA_ConnectionConfig));

    channel->receiveSequenceNumber = 0;

    channel->sendSequenceNumber = 0;

    /* Set the state to closed */

    channel->state = UA_SECURECHANNELSTATE_CLOSED;

    channel->renewState = UA_SECURECHANNELRENEWSTATE_NORMAL;

}

UA_StatusCode

UA_SecureChannel_processHELACK(UA_SecureChannel *channel,

                               const UA_TcpAcknowledgeMessage *remoteConfig) {

    /* The lowest common version is used by both sides */

    if(channel->config.protocolVersion > remoteConfig->protocolVersion)

        channel->config.protocolVersion = remoteConfig->protocolVersion;

    /* Can we receive the max send size? */

    if(channel->config.sendBufferSize > remoteConfig->receiveBufferSize)

        channel->config.sendBufferSize = remoteConfig->receiveBufferSize;

    /* Can we send the max receive size? */

    if(channel->config.recvBufferSize > remoteConfig->sendBufferSize)

        channel->config.recvBufferSize = remoteConfig->sendBufferSize;

    channel->config.remoteMaxMessageSize = remoteConfig->maxMessageSize;

    channel->config.remoteMaxChunkCount = remoteConfig->maxChunkCount;

    /* Chunks of at least 8192 bytes must be permissible.

     * See Part 6, Clause 6.7.1 */

    if(channel->config.recvBufferSize < 8192 ||

       channel->config.sendBufferSize < 8192 ||

       (channel->config.remoteMaxMessageSize != 0 &&

        channel->config.remoteMaxMessageSize < 8192))

        return UA_STATUSCODE_BADINTERNALERROR;

    return UA_STATUSCODE_GOOD;

}

/* Send an OPN message using asymmetric encryption.

 * Specification part 6, 6.7.4: The OpenSecureChannel Messages are signed and

 * encrypted if the SecurityMode is not None (even if the SecurityMode is

 * SignOnly). */

UA_StatusCode

UA_SecureChannel_sendOPN(UA_SecureChannel *channel,

                         UA_UInt32 requestId, const void *content,

                         const UA_DataType *contentType) {

    if(!content || !contentType)

        return UA_STATUSCODE_BADINTERNALERROR;

    /* The SecurityPolicy must be configured before sending OPN */

    const UA_SecurityPolicy *sp = channel->securityPolicy;

    UA_CHECK_MEM(sp, return UA_STATUSCODE_BADINTERNALERROR);

    /* Check for a valid security mode */

    UA_assert(channel->securityMode > UA_MESSAGESECURITYMODE_INVALID &&

              channel->securityMode <= UA_MESSAGESECURITYMODE_SIGNANDENCRYPT);

    /* The #None SecurityPolicy must use the NONE MessageSecurityMode.

     * All other SecurityPolicies must not. */

    UA_assert((sp->policyType == UA_SECURITYPOLICYTYPE_NONE) ==

              (channel->securityMode == UA_MESSAGESECURITYMODE_NONE));

    /* Can we use the connection manager? */

    UA_ConnectionManager *cm = channel->connectionManager;

    if(!UA_SecureChannel_isConnected(channel))

        return UA_STATUSCODE_BADCONNECTIONCLOSED;

    /* Allocate the message buffer */

    UA_ByteString buf = UA_BYTESTRING_NULL;

    UA_StatusCode res = cm->allocNetworkBuffer(cm, channel->connectionId, &buf,

                                               channel->config.sendBufferSize);

    UA_CHECK_STATUS(res, return res);

    /* Restrict buffer to the available space for the payload */

    UA_Byte *buf_pos = buf.data;

    const UA_Byte *buf_end = &buf.data[buf.length];

    hideBytesAsym(channel, &buf_pos, &buf_end);

    /* Define variables here to pacify some compilers wrt goto */

    size_t securityHeaderLength, pre_sig_length, total_length, encryptedLength;

    /* Encode the message type and content */

    UA_EncodeBinaryOptions encOpts;

    memset(&encOpts, 0, sizeof(UA_EncodeBinaryOptions));

    encOpts.namespaceMapping = channel->namespaceMapping;

    res |= UA_NodeId_encodeBinary(&contentType->binaryEncodingId, &buf_pos, buf_end);

    res |= UA_encodeBinaryInternal(content, contentType, &buf_pos, &buf_end,

                                   &encOpts, NULL, NULL);

    UA_CHECK_STATUS(res, goto error);

    /* Compute the header length */

    securityHeaderLength = calculateAsymAlgSecurityHeaderLength(channel);

    /* Add padding to the chunk */

    if(channel->securityMode != UA_MESSAGESECURITYMODE_NONE)

        padChunk(channel, &sp->asymSignatureAlgorithm, &sp->asymEncryptionAlgorithm,

                 &buf.data[UA_SECURECHANNEL_CHANNELHEADER_LENGTH + securityHeaderLength],

                 &buf_pos);

    /* The total message length */

    pre_sig_length = (uintptr_t)buf_pos - (uintptr_t)buf.data;

    total_length = pre_sig_length;

    if(channel->securityMode != UA_MESSAGESECURITYMODE_NONE)

        total_length += sp->asymSignatureAlgorithm.

            getLocalSignatureSize(sp, channel->channelContext);

    /* The total message length is known here which is why we encode the headers

     * at this step and not earlier. */

    res = prependHeadersAsym(channel, buf.data, buf_end, total_length,

                             securityHeaderLength, requestId, &encryptedLength);

    UA_CHECK_STATUS(res, goto error);

    /* Add the signature and encrypt the message */

    res = signAndEncryptAsym(channel, pre_sig_length, &buf,

                             securityHeaderLength, total_length);

    UA_CHECK_STATUS(res, goto error);

    /* Send the message, the buffer is freed in the network layer */

    buf.length = encryptedLength;

    return cm->sendWithConnection(cm, channel->connectionId, &UA_KEYVALUEMAP_NULL, &buf);

 error:

    cm->freeNetworkBuffer(cm, channel->connectionId, &buf);

    return res;

}

/* Will this chunk surpass the capacity of the SecureChannel for the message? */

static UA_StatusCode

adjustCheckMessageLimitsSym(UA_MessageContext *mc, size_t bodyLength) {

    mc->messageSizeSoFar += bodyLength;

    mc->chunksSoFar++;

    UA_SecureChannel *channel = mc->channel;

    if(mc->messageSizeSoFar > channel->config.localMaxMessageSize &&

       channel->config.localMaxMessageSize != 0)

        return UA_STATUSCODE_BADRESPONSETOOLARGE;

    if(mc->chunksSoFar > channel->config.localMaxChunkCount &&

       channel->config.localMaxChunkCount != 0)

        return UA_STATUSCODE_BADRESPONSETOOLARGE;

    return UA_STATUSCODE_GOOD;

}

static UA_StatusCode

encodeHeadersSym(UA_MessageContext *mc, size_t totalLength) {

    UA_SecureChannel *channel = mc->channel;

    UA_Byte *header_pos = mc->messageBuffer.data;

    UA_TcpMessageHeader header;

    header.messageTypeAndChunkType = mc->messageType;

    header.messageSize = (UA_UInt32)totalLength;

    if(mc->final)

        header.messageTypeAndChunkType += UA_CHUNKTYPE_FINAL;

    else

        header.messageTypeAndChunkType += UA_CHUNKTYPE_INTERMEDIATE;

    UA_SequenceHeader seqHeader;

    seqHeader.requestId = mc->requestId;

    seqHeader.sequenceNumber = UA_SecureChannel_nextSequenceNumber(channel);

    UA_StatusCode res = UA_STATUSCODE_GOOD;

    res |= UA_encodeBinaryInternal(&header, &UA_TRANSPORT[UA_TRANSPORT_TCPMESSAGEHEADER],

                                   &header_pos, &mc->buf_end, NULL, NULL, NULL);

    res |= UA_UInt32_encodeBinary(&channel->securityToken.channelId,

                                  &header_pos, mc->buf_end);

    res |= UA_UInt32_encodeBinary(&channel->securityToken.tokenId,

                                  &header_pos, mc->buf_end);

    res |= UA_encodeBinaryInternal(&seqHeader, &UA_TRANSPORT[UA_TRANSPORT_SEQUENCEHEADER],

                                   &header_pos, &mc->buf_end, NULL, NULL, NULL);

    return res;

}

static UA_StatusCode

sendSymmetricChunk(UA_MessageContext *mc) {

    UA_SecureChannel *channel = mc->channel;

    const UA_SecurityPolicy *sp = channel->securityPolicy;

    UA_ConnectionManager *cm = channel->connectionManager;

    if(!UA_SecureChannel_isConnected(channel))

        return UA_STATUSCODE_BADCONNECTIONCLOSED;

    /* The size of the message payload */

    size_t bodyLength = (uintptr_t)mc->buf_pos -

        (uintptr_t)&mc->messageBuffer.data[UA_SECURECHANNEL_SYMMETRIC_HEADER_TOTALLENGTH];

    /* Early-declare variables so we can use a goto in the error case */

    size_t total_length = 0;

    size_t pre_sig_length = 0;

    /* Check if chunk exceeds the limits for the overall message */

    UA_StatusCode res = adjustCheckMessageLimitsSym(mc, bodyLength);

    UA_CHECK_STATUS(res, goto error);

    UA_LOG_TRACE_CHANNEL(sp->logger, channel,

                         "Send from a symmetric message buffer of length %lu "

                         "a message of header+payload length of %lu",

                         (long unsigned int)mc->messageBuffer.length,

                         (long unsigned int)

                         ((uintptr_t)mc->buf_pos - (uintptr_t)mc->messageBuffer.data));

    /* Add padding if the message is encrypted (not for AEAD policies) */

    if(channel->securityMode == UA_MESSAGESECURITYMODE_SIGNANDENCRYPT &&

       !UA_SecurityPolicy_isAead(sp))

        padChunk(channel, &sp->symSignatureAlgorithm, &sp->symEncryptionAlgorithm,

                 &mc->messageBuffer.data[UA_SECURECHANNEL_SYMMETRIC_HEADER_UNENCRYPTEDLENGTH],

                 &mc->buf_pos);

    /* Compute the total message length */

    pre_sig_length = (uintptr_t)mc->buf_pos - (uintptr_t)mc->messageBuffer.data;

    total_length = pre_sig_length;

    if(channel->securityMode == UA_MESSAGESECURITYMODE_SIGN ||

       channel->securityMode == UA_MESSAGESECURITYMODE_SIGNANDENCRYPT)

        total_length += sp->symSignatureAlgorithm.

            getLocalSignatureSize(sp, channel->channelContext);

    UA_LOG_TRACE_CHANNEL(sp->logger, channel,

                         "Send from a symmetric message buffer of length %lu "

                         "a message of length %lu",

                         (long unsigned int)mc->messageBuffer.length,

                         (long unsigned int)total_length);

    /* Space for the padding and the signature have been reserved in setBufPos() */

    UA_assert(total_length <= channel->config.sendBufferSize);

    /* Adjust the buffer size of the network layer */

    mc->messageBuffer.length = total_length;

    /* Generate and encode the header for symmetric messages */

    res = encodeHeadersSym(mc, total_length);

    UA_CHECK_STATUS(res, goto error);

    /* Sign and encrypt the messge */

    res = signAndEncryptSym(mc, pre_sig_length, total_length);

    UA_CHECK_STATUS(res, goto error);

    /* Send the chunk. The buffer is freed in the network layer. If sending goes

     * wrong, the connection is removed in the next iteration of the

     * SecureChannel. Set the SecureChannel to closing already. */

    res = cm->sendWithConnection(cm, channel->connectionId,

                                 &UA_KEYVALUEMAP_NULL, &mc->messageBuffer);

    if(res != UA_STATUSCODE_GOOD && UA_SecureChannel_isConnected(channel))

        channel->state = UA_SECURECHANNELSTATE_CLOSING;

    return res;

 error:

    /* Free the unused message buffer */

    cm->freeNetworkBuffer(cm, channel->connectionId, &mc->messageBuffer);

    return res;

}

/* Callback from the encoding layer. Send the chunk and replace the buffer. */

static UA_StatusCode

sendSymmetricEncodingCallback(void *data, UA_Byte **buf_pos,

                              const UA_Byte **buf_end) {

    /* Set buf values from encoding in the messagecontext */

    UA_MessageContext *mc = (UA_MessageContext *)data;

    mc->buf_pos = *buf_pos;

    mc->buf_end = *buf_end;

    /* Send out */

    UA_StatusCode res = sendSymmetricChunk(mc);

    UA_CHECK_STATUS(res, return res);

    /* Set a new buffer for the next chunk */

    UA_ConnectionManager *cm = mc->channel->connectionManager;

    if(!UA_SecureChannel_isConnected(mc->channel))

        return UA_STATUSCODE_BADCONNECTIONCLOSED;

    res = cm->allocNetworkBuffer(cm, mc->channel->connectionId,

                                 &mc->messageBuffer,

                                 mc->channel->config.sendBufferSize);

    UA_CHECK_STATUS(res, return res);

    /* Hide bytes for header, padding and signature */

    setBufPos(mc);

    *buf_pos = mc->buf_pos;

    *buf_end = mc->buf_end;

    return UA_STATUSCODE_GOOD;

}

UA_StatusCode

UA_MessageContext_begin(UA_MessageContext *mc, UA_SecureChannel *channel,

                        UA_UInt32 requestId, UA_MessageType messageType) {

    UA_CHECK(messageType == UA_MESSAGETYPE_MSG || messageType == UA_MESSAGETYPE_CLO,

             return UA_STATUSCODE_BADINTERNALERROR);

    UA_ConnectionManager *cm = channel->connectionManager;

    if(!UA_SecureChannel_isConnected(channel))

        return UA_STATUSCODE_BADCONNECTIONCLOSED;

    /* Create the chunking info structure */

    mc->channel = channel;

    mc->requestId = requestId;

    mc->chunksSoFar = 0;

    mc->messageSizeSoFar = 0;

    mc->final = false;

    mc->messageBuffer = UA_BYTESTRING_NULL;

    mc->messageType = messageType;

    /* Allocate the message buffer */

    UA_StatusCode res =

        cm->allocNetworkBuffer(cm, channel->connectionId,

                               &mc->messageBuffer,

                               channel->config.sendBufferSize);

    UA_CHECK_STATUS(res, return res);

    /* Hide bytes for header, padding and signature */

    setBufPos(mc);

    return UA_STATUSCODE_GOOD;

}

UA_StatusCode

UA_MessageContext_encode(UA_MessageContext *mc, const void *content,

                         const UA_DataType *contentType) {

    UA_EncodeBinaryOptions encOpts;

    memset(&encOpts, 0, sizeof(UA_EncodeBinaryOptions));

    encOpts.namespaceMapping = mc->channel->namespaceMapping;

    UA_StatusCode res =

        UA_encodeBinaryInternal(content, contentType, &mc->buf_pos, &mc->buf_end,

                                &encOpts, sendSymmetricEncodingCallback, mc);

    if(res != UA_STATUSCODE_GOOD && mc->messageBuffer.length > 0)

        UA_MessageContext_abort(mc);

    return res;

}

UA_StatusCode

UA_MessageContext_finish(UA_MessageContext *mc) {

    mc->final = true;

    return sendSymmetricChunk(mc);

}

void

UA_MessageContext_abort(UA_MessageContext *mc) {

    UA_ConnectionManager *cm = mc->channel->connectionManager;

    if(!UA_SecureChannel_isConnected(mc->channel))

        return;

    cm->freeNetworkBuffer(cm, mc->channel->connectionId, &mc->messageBuffer);

}

/* Send a MSG or CLO message using symmetric encryption */

static UA_StatusCode

sendSymmetric(UA_SecureChannel *channel, UA_UInt32 requestId,

              UA_MessageType messageType, void *payload,

              const UA_DataType *payloadType) {

    if(!channel || !payload || !payloadType)

        return UA_STATUSCODE_BADINTERNALERROR;

    if(channel->state != UA_SECURECHANNELSTATE_OPEN)

        return UA_STATUSCODE_BADCONNECTIONCLOSED;

    UA_MessageContext mc;

    UA_StatusCode res = UA_MessageContext_begin(&mc, channel, requestId, messageType);

    UA_CHECK_STATUS(res, return res);

    /* Assert's required for clang-analyzer */

    UA_assert(mc.buf_pos ==

              &mc.messageBuffer.data[UA_SECURECHANNEL_SYMMETRIC_HEADER_TOTALLENGTH]);

    UA_assert(mc.buf_end <= &mc.messageBuffer.data[mc.messageBuffer.length]);

    res = UA_MessageContext_encode(&mc, &payloadType->binaryEncodingId,

                                   &UA_TYPES[UA_TYPES_NODEID]);

    UA_CHECK_STATUS(res, return res);

    res = UA_MessageContext_encode(&mc, payload, payloadType);

    UA_CHECK_STATUS(res, return res);

    return UA_MessageContext_finish(&mc);

}

UA_StatusCode

UA_SecureChannel_sendMSG(UA_SecureChannel *channel, UA_UInt32 requestId,

                         void *payload, const UA_DataType *payloadType) {

    return sendSymmetric(channel, requestId, UA_MESSAGETYPE_MSG,

                         payload, payloadType);

}

UA_StatusCode

UA_SecureChannel_sendCLO(UA_SecureChannel *channel, UA_UInt32 requestId,

                         UA_CloseSecureChannelRequest *req) {

    return sendSymmetric(channel, requestId, UA_MESSAGETYPE_CLO, req,

                         &UA_TYPES[UA_TYPES_CLOSESECURECHANNELREQUEST]);

}

/********************************/

/* Receive and Process Messages */

/********************************/

/* Does the sequence number match? Otherwise try to rollover. See Part 6,

 * Section 6.7.2.4 of the standard. */

#define UA_SEQUENCENUMBER_ROLLOVER 4294966271

UA_UInt32

UA_SecureChannel_nextSequenceNumber(UA_SecureChannel *channel) {

    /* channel->sendSequenceNumber mirrors the reference-stack counter: a

     * pre-increment value initialized to 0. The legacy scheme emits the

     * counter (first = 1); the non-legacy scheme emits counter-1 (first = 0). */

    UA_UInt64 next = (UA_UInt64)channel->sendSequenceNumber + 1;

    if(channel->legacySequenceNumbers) {

        /* Legacy rollover: the first number after the max is 1. */

        if(next > UA_SEQUENCENUMBER_ROLLOVER)

            next = 1;

        channel->sendSequenceNumber = (UA_UInt32)next;

        return channel->sendSequenceNumber;

    }

    /* Non-legacy: the counter wraps to 0 after UA_UINT32_MAX so the emitted

     * value (counter - 1) covers the full UInt32 range and then restarts at 0. */

    if(next > UA_UINT32_MAX)

        next = 0;

    channel->sendSequenceNumber = (UA_UInt32)next;

    return (channel->sendSequenceNumber == 0) ?

        UA_UINT32_MAX : (channel->sendSequenceNumber - 1);

}

#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION

static UA_StatusCode

processSequenceNumberSym(UA_SecureChannel *channel, UA_UInt32 sequenceNumber) {

    if(sequenceNumber != channel->receiveSequenceNumber + 1) {

        /* The non-legacy (ECC) rollover from UA_UINT32_MAX to 0 is already

         * accepted by the check above (unsigned overflow makes

         * receiveSequenceNumber + 1 == 0). Only the legacy "< 1024" rollover

         * needs the special case below; non-legacy policies reject anything

         * that is not the immediate successor. */

        if(!channel->legacySequenceNumbers ||

           channel->receiveSequenceNumber + 1 <= UA_SEQUENCENUMBER_ROLLOVER ||

           sequenceNumber >= 1024)

            return UA_STATUSCODE_BADSECURITYCHECKSFAILED;

        channel->receiveSequenceNumber = sequenceNumber - 1; /* Roll over */

    }

    ++channel->receiveSequenceNumber;

    return UA_STATUSCODE_GOOD;

}

#endif

static UA_StatusCode

unpackPayloadOPN(UA_SecureChannel *channel, UA_Chunk *chunk) {

    UA_assert(chunk->bytes.length >= UA_SECURECHANNEL_MESSAGE_MIN_LENGTH);

    size_t offset = UA_SECURECHANNEL_MESSAGEHEADER_LENGTH; /* Skip the message header */

    UA_UInt32 secureChannelId;

    UA_StatusCode res = UA_UInt32_decodeBinary(&chunk->bytes, &offset, &secureChannelId);

    UA_assert(res == UA_STATUSCODE_GOOD);

    UA_AsymmetricAlgorithmSecurityHeader asymHeader;

    res = UA_decodeBinaryInternal(&chunk->bytes, &offset, &asymHeader,

             &UA_TRANSPORT[UA_TRANSPORT_ASYMMETRICALGORITHMSECURITYHEADER], NULL);

    UA_CHECK_STATUS(res, return res);

    /* Declare before the first goto to avoid crosses-initialization in C++ */

    UA_SecurityPolicy *sp = NULL;

    /* Client/Server-specific processing. Creates a SecurityPolicy context and

     * attaches it to the channel. For the client, the remote certificate has

     * been verified before connecting. For the server the remote certificate is

     * verified within processOPNHeader. */

    UA_assert(channel->processOPNHeader);

    res = channel->processOPNHeader(channel->processOPNHeaderApplication,

                                    channel, &asymHeader);

    UA_CHECK_STATUS(res, goto error);

    /* On the client side, take the SecureChannelId from the first response */

    if(secureChannelId != 0 && channel->securityToken.channelId == 0)

        channel->securityToken.channelId = secureChannelId;

    /* Check the ChannelId */

#if !defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION)

    if(secureChannelId != channel->securityToken.channelId) {

        /* Allow the channel id to be different if the sent channel id is zero

         * and the SecurityToken is not initialized. This only happens on the

         * server side before we had a chance to tell the client which ChannelId

         * to use. */

        if(secureChannelId != 0 || channel->securityToken.tokenId != 0) {

            res = UA_STATUSCODE_BADSECURECHANNELIDINVALID;

            goto error;

        }

    }

#endif

    /* Generic header checking (for both client and server). Requires the

     * channel's SecurityPolicy. */

    res = checkAsymHeader(channel, &asymHeader);

    UA_CHECK_STATUS(res, goto error);

    UA_AsymmetricAlgorithmSecurityHeader_clear(&asymHeader);

    /* Decrypt the chunk payload */

    sp = channel->securityPolicy;

    res = decryptAndVerifyChunk(channel, &sp->asymSignatureAlgorithm,

                                &sp->asymEncryptionAlgorithm,

                                chunk->messageType, &chunk->bytes, offset);

    UA_CHECK_STATUS(res, return res);

    /* Decode the SequenceHeader */

    UA_SequenceHeader sequenceHeader;

    res = UA_decodeBinaryInternal(&chunk->bytes, &offset, &sequenceHeader,

                                  &UA_TRANSPORT[UA_TRANSPORT_SEQUENCEHEADER], NULL);

    UA_CHECK_STATUS(res, return res);

    /* Set the sequence number for the channel from which to count up */

    channel->receiveSequenceNumber = sequenceHeader.sequenceNumber;

    chunk->requestId = sequenceHeader.requestId; /* Set the RequestId of the chunk */

    /* Use only the payload */

    chunk->bytes.data += offset;

    chunk->bytes.length -= offset;

    return UA_STATUSCODE_GOOD;

error:

    UA_AsymmetricAlgorithmSecurityHeader_clear(&asymHeader);

    return res;

}

static UA_StatusCode

unpackPayloadMSG(UA_SecureChannel *channel, UA_Chunk *chunk,

                 UA_DateTime nowMonotonic) {

    UA_CHECK_MEM(channel->securityPolicy, return UA_STATUSCODE_BADINTERNALERROR);

    UA_assert(chunk->bytes.length >= UA_SECURECHANNEL_MESSAGE_MIN_LENGTH);

    size_t offset = UA_SECURECHANNEL_MESSAGEHEADER_LENGTH; /* Skip the message header */

    UA_UInt32 secureChannelId;

    UA_UInt32 tokenId; /* SymmetricAlgorithmSecurityHeader */

    UA_StatusCode res = UA_STATUSCODE_GOOD;

    res |= UA_UInt32_decodeBinary(&chunk->bytes, &offset, &secureChannelId);

    res |= UA_UInt32_decodeBinary(&chunk->bytes, &offset, &tokenId);

    UA_assert(offset == UA_SECURECHANNEL_MESSAGE_MIN_LENGTH);

    UA_assert(res == UA_STATUSCODE_GOOD);

#if !defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION)

    /* Check the ChannelId. Non-opened channels have the id zero. */

    if(secureChannelId != channel->securityToken.channelId)

        return UA_STATUSCODE_BADSECURECHANNELIDINVALID;

#endif

    /* Check (and revolve) the SecurityToken */

    res = checkSymHeader(channel, tokenId, nowMonotonic);

    UA_CHECK_STATUS(res, return res);

    /* Decrypt the chunk payload */

    UA_SecurityPolicy *sp = channel->securityPolicy;

    res = decryptAndVerifyChunk(channel, &sp->symSignatureAlgorithm,

                                &sp->symEncryptionAlgorithm,

                                chunk->messageType, &chunk->bytes, offset);

    UA_CHECK_STATUS(res, return res);

    /* Check the sequence number. Skip sequence number checking for fuzzer to

     * improve coverage */

    UA_SequenceHeader sequenceHeader;

    res = UA_decodeBinaryInternal(&chunk->bytes, &offset, &sequenceHeader,

                                  &UA_TRANSPORT[UA_TRANSPORT_SEQUENCEHEADER], NULL);

#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION

    res |= processSequenceNumberSym(channel, sequenceHeader.sequenceNumber);

#endif

    UA_CHECK_STATUS(res, return res);

    chunk->requestId = sequenceHeader.requestId; /* Set the RequestId of the chunk */

    /* Use only the payload */

    chunk->bytes.data += offset;

    chunk->bytes.length -= offset;

    return UA_STATUSCODE_GOOD;

}

static UA_StatusCode

extractCompleteChunk(UA_SecureChannel *channel, UA_Chunk *chunk,

                     UA_DateTime nowMonotonic) {

    /* At least 8 byte needed for the header */

    size_t offset = channel->unprocessedOffset;

    size_t remaining = channel->unprocessed.length - offset;

    if(remaining < UA_SECURECHANNEL_MESSAGEHEADER_LENGTH)

        return UA_STATUSCODE_GOOD;

    /* Decoding the header cannot fail */

    UA_TcpMessageHeader hdr;

    UA_StatusCode res =

        UA_decodeBinaryInternal(&channel->unprocessed, &offset, &hdr,

                                &UA_TRANSPORT[UA_TRANSPORT_TCPMESSAGEHEADER], NULL);

    UA_assert(res == UA_STATUSCODE_GOOD);

    (void)res; /* pacify compilers if assert is ignored */

    UA_MessageType msgType = (UA_MessageType)

        (hdr.messageTypeAndChunkType & UA_BITMASK_MESSAGETYPE);

    UA_ChunkType chunkType = (UA_ChunkType)

        (hdr.messageTypeAndChunkType & UA_BITMASK_CHUNKTYPE);

    /* The message size is not allowed */

    if(hdr.messageSize < UA_SECURECHANNEL_MESSAGE_MIN_LENGTH)

        return UA_STATUSCODE_BADTCPMESSAGETYPEINVALID;

    if(hdr.messageSize > channel->config.recvBufferSize)

        return UA_STATUSCODE_BADTCPMESSAGETOOLARGE;

    /* Incomplete chunk. Continue processing later. */

    if(hdr.messageSize > remaining)

        return UA_STATUSCODE_GOOD;

    /* Set the chunk information */

    chunk->bytes.data = channel->unprocessed.data + channel->unprocessedOffset;

    chunk->bytes.length = hdr.messageSize;

    chunk->messageType = msgType;

    chunk->chunkType = chunkType;

    chunk->requestId = 0;

    chunk->copied = false;

    /* Increase the unprocessed offset */

    channel->unprocessedOffset += hdr.messageSize;

    /* Validate, decrypt and unpack the chunk payload */

    switch(msgType) {

    case UA_MESSAGETYPE_OPN:

        if(chunkType != UA_CHUNKTYPE_FINAL)

            return UA_STATUSCODE_BADTCPMESSAGETYPEINVALID;

        if(channel->state != UA_SECURECHANNELSTATE_OPEN &&

           channel->state != UA_SECURECHANNELSTATE_OPN_SENT &&

           channel->state != UA_SECURECHANNELSTATE_ACK_SENT)

            return UA_STATUSCODE_BADINVALIDSTATE;

        res = unpackPayloadOPN(channel, chunk);

        break;

    case UA_MESSAGETYPE_MSG:

    case UA_MESSAGETYPE_CLO:

        if(chunkType != UA_CHUNKTYPE_FINAL &&

           chunkType != UA_CHUNKTYPE_INTERMEDIATE &&

           chunkType != UA_CHUNKTYPE_ABORT)

            return UA_STATUSCODE_BADTCPMESSAGETYPEINVALID;

        if(channel->state != UA_SECURECHANNELSTATE_OPEN)

            return UA_STATUSCODE_BADINVALIDSTATE;

        res = unpackPayloadMSG(channel, chunk, nowMonotonic);

        break;

    case UA_MESSAGETYPE_RHE:

    case UA_MESSAGETYPE_HEL:

    case UA_MESSAGETYPE_ACK:

    case UA_MESSAGETYPE_ERR:

        if(chunkType != UA_CHUNKTYPE_FINAL)

            return UA_STATUSCODE_BADTCPMESSAGETYPEINVALID;

        /* Hide the message header */

        chunk->bytes.data += UA_SECURECHANNEL_MESSAGEHEADER_LENGTH;

        chunk->bytes.length -= UA_SECURECHANNEL_MESSAGEHEADER_LENGTH;

        break;

    default:

        res = UA_STATUSCODE_BADTCPMESSAGETYPEINVALID;

        break;

    }

    return res;

}

UA_StatusCode

UA_SecureChannel_loadBuffer(UA_SecureChannel *channel, const UA_ByteString buffer) {

    /* Append to the previous unprocessed buffer */

    if(channel->unprocessed.length > 0) {

        UA_assert(channel->unprocessedCopied == true);

        UA_Byte *t = (UA_Byte*)

            UA_realloc(channel->unprocessed.data,

                       channel->unprocessed.length + buffer.length);

        if(!t)

            return UA_STATUSCODE_BADOUTOFMEMORY;

        if(buffer.length)

            memcpy(t + channel->unprocessed.length, buffer.data, buffer.length);

        channel->unprocessed.data = t;

        channel->unprocessed.length += buffer.length;

        return UA_STATUSCODE_GOOD;

    }

    /* Use the new buffer directly */

    channel->unprocessed = buffer;

    channel->unprocessedCopied = false;

    return UA_STATUSCODE_GOOD;

}