With endfirst writing, it could be that we want to abandon any zero
length sub-packet. That's what WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH
was supposed to make happen, but the DER length writing code didn't
look at that flag. Now it does.
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/11703)
This means the WPACKET API can be used for calculating the number of
bytes that would have been written if a non-NULL buffer had been used.
This enables us to calculate the number of length bytes required when
encoding ASN.1
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9111)
