| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | SSL_check_chain - check certificate chain suitability
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/ssl.h>
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| 10 |
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| 11 | int SSL_check_chain(SSL *s, X509 *x, EVP_PKEY *pk, STACK_OF(X509) *chain);
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| 12 |
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| 13 | =head1 DESCRIPTION
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| 14 |
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| 15 | SSL_check_chain() checks whether certificate B<x>, private key B<pk> and
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| 16 | certificate chain B<chain> is suitable for use with the current session
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| 17 | B<s>.
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| 18 |
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| 19 | =head1 RETURN VALUES
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| 20 |
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| 21 | SSL_check_chain() returns a bitmap of flags indicating the validity of the
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| 22 | chain.
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| 23 |
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| 24 | B<CERT_PKEY_VALID>: the chain can be used with the current session.
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| 25 | If this flag is B<not> set then the certificate will never be used even
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| 26 | if the application tries to set it because it is inconsistent with the
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| 27 | peer preferences.
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| 28 |
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| 29 | B<CERT_PKEY_SIGN>: the EE key can be used for signing.
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| 30 |
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| 31 | B<CERT_PKEY_EE_SIGNATURE>: the signature algorithm of the EE certificate is
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| 32 | acceptable.
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| 33 |
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| 34 | B<CERT_PKEY_CA_SIGNATURE>: the signature algorithms of all CA certificates
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| 35 | are acceptable.
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| 36 |
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| 37 | B<CERT_PKEY_EE_PARAM>: the parameters of the end entity certificate are
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| 38 | acceptable (e.g. it is a supported curve).
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| 39 |
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| 40 | B<CERT_PKEY_CA_PARAM>: the parameters of all CA certificates are acceptable.
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| 41 |
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| 42 | B<CERT_PKEY_EXPLICIT_SIGN>: the end entity certificate algorithm
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| 43 | can be used explicitly for signing (i.e. it is mentioned in the signature
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| 44 | algorithms extension).
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| 45 |
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| 46 | B<CERT_PKEY_ISSUER_NAME>: the issuer name is acceptable. This is only
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| 47 | meaningful for client authentication.
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| 48 |
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| 49 | B<CERT_PKEY_CERT_TYPE>: the certificate type is acceptable. Only meaningful
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| 50 | for client authentication.
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| 51 |
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| 52 | B<CERT_PKEY_SUITEB>: chain is suitable for Suite B use.
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| 53 |
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| 54 | =head1 NOTES
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| 55 |
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| 56 | SSL_check_chain() must be called in servers after a client hello message or in
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| 57 | clients after a certificate request message. It will typically be called
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| 58 | in the certificate callback.
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| 59 |
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| 60 | An application wishing to support multiple certificate chains may call this
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| 61 | function on each chain in turn: starting with the one it considers the
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| 62 | most secure. It could then use the chain of the first set which returns
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| 63 | suitable flags.
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| 64 |
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| 65 | As a minimum the flag B<CERT_PKEY_VALID> must be set for a chain to be
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| 66 | usable. An application supporting multiple chains with different CA signature
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| 67 | algorithms may also wish to check B<CERT_PKEY_CA_SIGNATURE> too. If no
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| 68 | chain is suitable a server should fall back to the most secure chain which
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| 69 | sets B<CERT_PKEY_VALID>.
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| 70 |
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| 71 | The validity of a chain is determined by checking if it matches a supported
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| 72 | signature algorithm, supported curves and in the case of client authentication
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| 73 | certificate types and issuer names.
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| 74 |
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| 75 | Since the supported signature algorithms extension is only used in TLS 1.2,
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| 76 | TLS 1.3 and DTLS 1.2 the results for earlier versions of TLS and DTLS may not
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| 77 | be very useful. Applications may wish to specify a different "legacy" chain
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| 78 | for earlier versions of TLS or DTLS.
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| 79 |
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| 80 | =head1 SEE ALSO
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| 81 |
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| 82 | L<SSL_CTX_set_cert_cb(3)>,
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| 83 | L<ssl(7)>
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| 84 |
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| 85 | =head1 COPYRIGHT
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| 86 |
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| 87 | Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.
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| 88 |
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| 89 | Licensed under the OpenSSL license (the "License"). You may not use
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| 90 | this file except in compliance with the License. You can obtain a copy
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| 91 | in the file LICENSE in the source distribution or at
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| 92 | L<https://www.openssl.org/source/license.html>.
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| 93 |
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| 94 | =cut
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