Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

SSL_check_chain(3)                  OpenSSL                 SSL_check_chain(3)

       SSL_check_chain - check certificate chain suitability

       libcrypto, -lcrypto

        #include <openssl/ssl.h>

        int SSL_check_chain(SSL *s, X509 *x, EVP_PKEY *pk, STACK_OF(X509) *chain);

       SSL_check_chain() checks whether certificate x, private key pk and
       certificate chain chain is suitable for use with the current session s.

       SSL_check_chain() returns a bitmap of flags indicating the validity of
       the chain.

       CERT_PKEY_VALID: the chain can be used with the current session.  If
       this flag is not set then the certificate will never be used even if
       the application tries to set it because it is inconsistent with the
       peer preferences.

       CERT_PKEY_SIGN: the EE key can be used for signing.

       CERT_PKEY_EE_SIGNATURE: the signature algorithm of the EE certificate
       is acceptable.

       CERT_PKEY_CA_SIGNATURE: the signature algorithms of all CA certificates
       are acceptable.

       CERT_PKEY_EE_PARAM: the parameters of the end entity certificate are
       acceptable (e.g. it is a supported curve).

       CERT_PKEY_CA_PARAM: the parameters of all CA certificates are

       CERT_PKEY_EXPLICIT_SIGN: the end entity certificate algorithm can be
       used explicitly for signing (i.e. it is mentioned in the signature
       algorithms extension).

       CERT_PKEY_ISSUER_NAME: the issuer name is acceptable. This is only
       meaningful for client authentication.

       CERT_PKEY_CERT_TYPE: the certificate type is acceptable. Only
       meaningful for client authentication.

       CERT_PKEY_SUITEB: chain is suitable for Suite B use.

       SSL_check_chain() must be called in servers after a client hello
       message or in clients after a certificate request message. It will
       typically be called in the certificate callback.

       An application wishing to support multiple certificate chains may call
       this function on each chain in turn: starting with the one it considers
       the most secure. It could then use the chain of the first set which
       returns suitable flags.

       As a minimum the flag CERT_PKEY_VALID must be set for a chain to be
       usable. An application supporting multiple chains with different CA
       signature algorithms may also wish to check CERT_PKEY_CA_SIGNATURE too.
       If no chain is suitable a server should fall back to the most secure
       chain which sets CERT_PKEY_VALID.

       The validity of a chain is determined by checking if it matches a
       supported signature algorithm, supported curves and in the case of
       client authentication certificate types and issuer names.

       Since the supported signature algorithms extension is only used in TLS
       1.2, TLS 1.3 and DTLS 1.2 the results for earlier versions of TLS and
       DTLS may not be very useful. Applications may wish to specify a
       different "legacy" chain for earlier versions of TLS or DTLS.

       SSL_CTX_set_cert_cb(3), ssl(7)

       Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at

1.1.1i                            2018-09-23                SSL_check_chain(3)