2015-07-23 15:38:58 +00:00
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=pod
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=head1 NAME
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SSL_check_chain - check certificate chain suitability
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_check_chain(SSL *s, X509 *x, EVP_PKEY *pk, STACK_OF(X509) *chain);
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=head1 DESCRIPTION
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SSL_check_chain() checks whether certificate B<x>, private key B<pk> and
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certificate chain B<chain> is suitable for use with the current session
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B<s>.
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=head1 RETURN VALUES
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SSL_check_chain() returns a bitmap of flags indicating the validity of the
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chain.
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B<CERT_PKEY_VALID>: the chain can be used with the current session.
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If this flag is B<not> set then the certificate will never be used even
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if the application tries to set it because it is inconsistent with the
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peer preferences.
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B<CERT_PKEY_SIGN>: the EE key can be used for signing.
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B<CERT_PKEY_EE_SIGNATURE>: the signature algorithm of the EE certificate is
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acceptable.
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B<CERT_PKEY_CA_SIGNATURE>: the signature algorithms of all CA certificates
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are acceptable.
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B<CERT_PKEY_EE_PARAM>: the parameters of the end entity certificate are
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acceptable (e.g. it is a supported curve).
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B<CERT_PKEY_CA_PARAM>: the parameters of all CA certificates are acceptable.
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B<CERT_PKEY_EXPLICIT_SIGN>: the end entity certificate algorithm
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can be used explicitly for signing (i.e. it is mentioned in the signature
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algorithms extension).
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B<CERT_PKEY_ISSUER_NAME>: the issuer name is acceptable. This is only
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meaningful for client authentication.
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B<CERT_PKEY_CERT_TYPE>: the certificate type is acceptable. Only meaningful
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for client authentication.
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B<CERT_PKEY_SUITEB>: chain is suitable for Suite B use.
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=head1 NOTES
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SSL_check_chain() must be called in servers after a client hello message or in
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clients after a certificate request message. It will typically be called
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in the certificate callback.
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An application wishing to support multiple certificate chains may call this
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function on each chain in turn: starting with the one it considers the
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most secure. It could then use the chain of the first set which returns
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suitable flags.
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As a minimum the flag B<CERT_PKEY_VALID> must be set for a chain to be
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usable. An application supporting multiple chains with different CA signature
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algorithms may also wish to check B<CERT_PKEY_CA_SIGNATURE> too. If no
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chain is suitable a server should fall back to the most secure chain which
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sets B<CERT_PKEY_VALID>.
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The validity of a chain is determined by checking if it matches a supported
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signature algorithm, supported curves and in the case of client authentication
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certificate types and issuer names.
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Since the supported signature algorithms extension is only used in TLS 1.2
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and DTLS 1.2 the results for earlier versions of TLS and DTLS may not be
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very useful. Applications may wish to specify a different "legacy" chain
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for earlier versions of TLS or DTLS.
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=head1 SEE ALSO
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2015-08-17 19:21:33 +00:00
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L<SSL_CTX_set_cert_cb(3)>,
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L<ssl(3)>
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2015-07-23 15:38:58 +00:00
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=cut
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