Cannot create a signed message in detached mode

[hmueller314]

I am trying to create a sign1 message in detached mode. According to rfc8152 this is done by using a "nil" value for the message content. Following your example code I am inserting a node of the form

node = cn_cbor_data_create(NULL, 0, CBOR_CONTEXT_PARAM_COMMA NULL);
node->type = CN_CBOR_NULL;

for the message content in your json parser (test/json.cpp) but I cannot create a signed message because the call to COSE_Sign1_SetContent fails.

[hmueller314]

I think I found a solution. For detached mode follow the "normal" flow, for example BuildSign1Message in Sign_test.cpp. Before encoding the message (e.g. using COSE_Encode(hSignObj.ToCOSE(), nullptr, 0, 0)) replace the payload with a "nil" value. This can be done using the following code fragment:

COSE_Sign1Message* pMessage = (COSE_Sign1Message*)h;
cn_cbor* cb_value = cn_cbor_null_create(CBOR_CONTEXT_PARAM_COMMA nullptr);
_COSE_array_replace(&pMessage->m_message, cb_value, INDEX_BODY, CBOR_CONTEXT_PARAM_COMMA nullptr);