OpenSecureChannel request

Note

Add more information about: * ua time format * the Construct * openSSL

The OPC UA OpenSecureChannel request

The OpenSecureChannel request contains the following fields:

Parameter	Datatype	Value	Comments
MessageType	3 ACII bytes	OPN	from Open
IsFinal	1 ASCII byte	F	from final
MessageSize	ULInt32
SecureChannelId	ULInt32
SecurityPolicyUriLength	ULInt32
SecurityPolicyUri	String	NONE [SecPol]	utf-8 encoded.
SenderCertificateLength	ULInt32
SenderCertificate	Array of bytes	a DER encoded blob
ReceiverCertificateThumbprintLength	ULInt32
ReceiverCertificateThumbprint	Array of bytes
Sequencenumber	ULInt32
RequestId	ULInt32
EncodingByte	ULInt8 (ENUM)
NameSpace	Byte
Identifier	UInt16
AuthenticationTokenEncodingByte	Byte
AuthenticationTokenIdentifier	Byte
TimeStamp	ULInt64
RequestHandle	ULInt32
ReturnDiagnostics	ULInt32
AuditEntryId	String
TimeOutHint	ULInt32
AHEncodingByte	ULInt8 (ENUM)
AHIdentifier	Byte
AHEncoding	Byte
ProtocolVersion	ULInt32
RequestType	ULInt32
SecurityMode	ULInt32
ClientNonce	ULInt32
RequestedLifetime	ULInt32

Construct

Using Construct we can create a struct, containing these fields.

from construct import *

c = Struct('OPC UASC OpenSecureChannel Request',

            String('MessageType', 3),
            String('IsFinal', 1),
            ULInt32('MessageSize'),
            ULInt32('SecureChannelId'),
            PascalString('SecurityPolicyUri', length_field=ULInt32('length')),
            SLInt32('SenderCertificateLength'),
            Bytes('SenderCertificate', lambda ctx:ctx['SenderCertificateLength']),
            SLInt32('ReceiverCertificateThumbprintLength'),
            Bytes('ReceiverCertificateThumbprint', lambda ctx:ctx['ReceiverCertificateThumbprintLength']),
            ULInt32('SequenceNumber'),
            ULInt32('RequestId'),
            ULInt8('EncodingByte'),
            ULInt8('NameSpace'),
            ULInt16('Identifier'),
            ULInt8('AuthenticationTokenEncodingByte'),
            ULInt8('AuthenticationTokenIdentifier'),
            ULInt64('TimeStamp'),
            ULInt32('RequestHandle'),
            ULInt32('ReturnDiagnostics'),
            PascalString('AuditEntryId',
                         length_field=ULInt32('length'),
                         encoding='utf8'),
            ULInt32('TimeOutHint'),
            ULInt8('AHEncodingByte'),# AdditionalHeader
            ULInt8('AHIdentifier'),
            ULInt8('AHEncoding'),
            ULInt32('ProtocolVersion'),
            ULInt32('RequestType'),
            ULInt32('SecurityMode'),
            ULInt32('ClientNonce'),
            ULInt32('RequestedLifetime'),
        )

Snippets

[SecPol]

The correct URL is something like: http://opcfoundation.org/UA/SecurityPolicy#None