Clarify why SSL_CTX_use_certificate_chain_file() should be preferred.

L<SSL_clear(3)|SSL_clear(3)> is called for this SSL object.

SSL_CTX_use_certificate() loads the certificate B<x> into B<ctx>,

SSL_use_certificate() loads B<x> into B<ssl>.

SSL_use_certificate() loads B<x> into B<ssl>. The rest of the

certificates needed to form the complete certificate chain can be

specified using the

L<SSL_CTX_add_extra_chain_cert(3)|SSL_CTX_add_extra_chain_cert(3)>

function.

SSL_CTX_use_certificate_ASN1() loads the ASN1 encoded certificate from

the memory location B<d> (with length B<len>) into B<ctx>,

into B<ctx>. The formatting B<type> of the certificate must be specified

from the known types SSL_FILETYPE_PEM, SSL_FILETYPE_ASN1.

SSL_use_certificate_file() loads the certificate from B<file> into B<ssl>.

See the NOTES section on why SSL_CTX_use_certificate_chain_file()

should be preferred.

SSL_CTX_use_certificate_chain_file() loads a certificate chain from 

B<file> into B<ctx>. The certificates must be in PEM format and must

to the store of chain certificates using

L<SSL_CTX_add_extra_chain_cert(3)|SSL_CTX_add_extra_chain_cert(3)>.

There exists only one extra chain store, so that the same chain is appended

to both types of certificates, RSA and DSA!

to both types of certificates, RSA and DSA! If it is not intented to use

both type of certificate at the same time, it is recommended to use the

SSL_CTX_use_certificate_chain_file() instead of the

SSL_CTX_use_certificate_file() function in order to allow the use of

complete certificate chains even when no trusted CA storage is used or

when the CA issuing the certificate shall not be added to the trusted

CA storage.

If additional certificates are needed to complete the chain during the

TLS negotiation, CA certificates are additionally looked up in the