SSL_CTX_set_max_cert_list() sets the maximum size allowed for the peers
certificate chain for all SSL objects created from ctx to be <size> bytes.
The SSL objects inherit the setting valid for ctx at the time
SSL_new(3) is being called.
SSL_CTX_get_max_cert_list() returns the currently set maximum size for ctx.
SSL_set_max_cert_list() sets the maximum size allowed for the peers
certificate chain for ssl to be <size> bytes. This setting stays valid
until a new value is set.
SSL_get_max_cert_list() returns the currently set maximum size for ssl.
During the handshake process, the peer may send a certificate chain.
The TLS/SSL standard does not give any maximum size of the certificate chain.
The OpenSSL library handles incoming data by a dynamically allocated buffer.
In order to prevent this buffer from growing without bounds due to data
received from a faulty or malicious peer, a maximum size for the certificate
chain is set.
The default value for the maximum certificate chain size is 100kB (30kB
on the 16bit DOS platform). This should be sufficient for usual certificate
chains (OpenSSLs default maximum chain length is 10, see
SSL_CTX_set_verify(3), and certificates
without special extensions have a typical size of 1-2kB).
For special applications it can be necessary to extend the maximum certificate
chain size allowed to be sent by the peer, see e.g. the work on
Internet X.509 Public Key Infrastructure Proxy Certificate Profile
and TLS Delegation Protocol at http://www.ietf.org/ and
Under normal conditions it should never be necessary to set a value smaller
than the default, as the buffer is handled dynamically and only uses the
memory actually required by the data sent by the peer.
If the maximum certificate chain size allowed is exceeded, the handshake will
fail with a SSL_R_EXCESSIVE_MESSAGE_SIZE error.