NAME
SSL_CTX_set_max_cert_list,
SSL_CTX_get_max_cert_list,
SSL_set_max_cert_list,
SSL_get_max_cert_list —
manipulate allowed size for the peer's
certificate chain
SYNOPSIS
#include
<openssl/ssl.h>
long
SSL_CTX_set_max_cert_list(SSL_CTX
*ctx, long
size);
long
SSL_CTX_get_max_cert_list(SSL_CTX
*ctx);
long
SSL_set_max_cert_list(SSL
*ssl, long
size);
long
SSL_get_max_cert_list(SSL
*ctx);
DESCRIPTION
SSL_CTX_set_max_cert_list()
sets the maximum size allowed for the peer's 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 peer's 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 bound 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 (OpenSSL's 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 for example the work on Internet X.509 Public Key Infrastructure Proxy Certificate Profile and TLS Delegation Protocol at https://www.ietf.org/ and http://www.globus.org/.
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.
RETURN VALUES
SSL_CTX_set_max_cert_list() and
SSL_set_max_cert_list() return the previously set
value.
SSL_CTX_get_max_cert_list() and
SSL_get_max_cert_list() return the currently set
value.
SEE ALSO
HISTORY
These functions first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.