From RFC6376 #page-29, it says:
In hash step 1, the Signer/Verifier MUST hash the message body, canonicalized using the body canonicalization algorithm specified in the "c=" tag and then truncated to the length specified in the "l=" tag.
From Wikipedia DomainKeys Identified Mail, it says:
Both header and body contribute to the signature. First, the message body is hashed, always from the beginning, possibly truncated at a given length (which may be zero)...
- What's the default value of the
l=tag? Does the whole message body get hashed? If not the whole body message get hashed, then may an attacker modify the unhashed part of the body message and pass DKIM check?
....No data integrity is implied.
From RFC6376 #section-1.5:
Verifying the signature asserts that the hashed content has not changed since it was signed and asserts nothing else about "protecting" the end-to-end integrity of the message.
- Why is it saying that DKIM doesn't ensure data integrity? Isn't "hashed content has not changed" == "data integrity"?