SSL_check_chain(3)

NAME

       SSL_check_chain - check certificate chain suitability

SYNOPSIS

        #include <openssl/ssl.h>

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

DESCRIPTION

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

RETURN VALUES

       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 accept-
       able.

       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 meaning-
       ful for client authentication.

       CERT_PKEY_SUITEB: chain is suitable for Suite B use.

NOTES

       SSL_check_chain() must be called in servers after a client hello mes-
       sage or in clients after a certificate request message. It will typi-
       cally 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 sup-
       ported 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 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.

SEE ALSO

       SSL_CTX_set_cert_cb(3), ssl(3)

1.0.2t                            2019-09-10                SSL_check_chain(3)