Make maximum certifcate chain size accepted from the peer application

settable (proposed by "Douglas E. Engert" <deengert@anl.gov>).

2 files changed, 78 insertions, 0 deletions

diff --git a/doc/ssl/SSL_CTX_set_max_cert_list.pod b/doc/ssl/SSL_CTX_set_max_cert_list.pod
new file mode 100644
index 0000000000..da68cb9fc2
--- /dev/null
+++ b/doc/ssl/SSL_CTX_set_max_cert_list.pod
@@ -0,0 +1,77 @@
+=pod
+
+=head1 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 for the peer's certificate chain
+
+=head1 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);
+
+=head1 DESCRIPTION
+
+SSL_CTX_set_max_cert_list() sets the maximum size allowed for the peer's
+certificate chain for all SSL objects created from B<ctx> to be <size> bytes.
+The SSL objects inherit the setting valid for B<ctx> at the time
+L<SSL_new(3)|SSL_new(3)> is being called.
+
+SSL_CTX_get_max_cert_list() returns the currently set maximum size for B<ctx>.
+
+SSL_set_max_cert_list() sets the maximum size allowed for the peer's
+certificate chain for B<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 B<ssl>.
+
+=head1 NOTES
+
+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 (OpenSSL's default maximum chain length is 10, see
+L<SSL_CTX_set_verify(3)|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
+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.
+
+=head1 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.
+
+=head1 SEE ALSO
+
+L<ssl(3)|ssl(3)>, L<SSL_new(3)|SSL_new(3)>,
+L<SSL_CTX_set_verify(3)|SSL_CTX_set_verify(3)>
+
+=head1 HISTORY
+
+SSL*_set/get_max_cert_list() have been introduced in OpenSSL 0.9.7.
+
+=cut
diff --git a/doc/ssl/ssl.pod b/doc/ssl/ssl.pod
index 6845f4f76d..89b321edec 100644
--- a/doc/ssl/ssl.pod
+++ b/doc/ssl/ssl.pod
@@ -669,6 +669,7 @@ L<SSL_CTX_set_client_CA_list(3)|SSL_CTX_set_client_CA_list(3)>,
 L<SSL_CTX_set_default_passwd_cb(3)|SSL_CTX_set_default_passwd_cb(3)>,
 L<SSL_CTX_set_generate_session_id(3)|SSL_CTX_set_generate_session_id(3)>,
 L<SSL_CTX_set_info_callback(3)|SSL_CTX_set_info_callback(3)>,
+L<SSL_CTX_set_max_cert_list(3)|SSL_CTX_set_max_cert_list(3)>,
 L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>,
 L<SSL_CTX_set_options(3)|SSL_CTX_set_options(3)>,
 L<SSL_CTX_set_quiet_shutdown(3)|SSL_CTX_set_quiet_shutdown(3)>,