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131 lines
4.1 KiB
Plaintext
131 lines
4.1 KiB
Plaintext
=pod
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=head1 NAME
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X509_get_extension_flags, X509_get_key_usage, X509_get_extended_key_usage -
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retrieve certificate extension flags.
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=head1 SYNOPSIS
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#include <openssl/x509v3.h>
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uint32_t X509_get_extension_flags(X509 *x);
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uint32_t X509_get_key_usage(X509 *x);
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uint32_t X509_get_extended_key_usage(X509 *x);
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const ASN1_OCTET_STRING *X509_get0_subject_key_id(X509 *x);
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=head1 DESCRIPTION
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These functions retrieve flags related to commonly used certificate extensions.
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X509_get_extension_flags() retrieves general information about a certificate,
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it will return one or more of the following flags ored together.
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=over 4
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=item B<EXFLAG_V1>
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The certificate is an obsolete version 1 certificate.
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=item B<EXFLAG_BCONS>
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The certificate contains a basic constraints extension.
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=item B<EXFLAG_CA>
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The certificate contains basic constraints and asserts the CA flag.
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=item B<EXFLAG_PROXY>
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The certificate is a valid proxy certificate.
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=item B<EXFLAG_SI>
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The certificate is self issued (that is subject and issuer names match).
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=item B<EXFLAG_SS>
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The subject and issuer names match and extension values imply it is self
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signed.
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=item B<EXFLAG_FRESHEST>
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The freshest CRL extension is present in the certificate.
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=item B<EXFLAG_CRITICAL>
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The certificate contains an unhandled critical extension.
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=item B<EXFLAG_INVALID>
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Some certificate extension values are invalid or inconsistent. The
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certificate should be rejected.
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=item B<EXFLAG_KUSAGE>
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The certificate contains a key usage extension. The value can be retrieved
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using X509_get_key_usage().
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=item B<EXFLAG_XKUSAGE>
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The certificate contains an extended key usage extension. The value can be
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retrieved using X509_get_extended_key_usage().
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=back
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X509_get_key_usage() returns the value of the key usage extension. If key
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usage is present will return zero or more of the flags:
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B<KU_DIGITAL_SIGNATURE>, B<KU_NON_REPUDIATION>, B<KU_KEY_ENCIPHERMENT>,
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B<KU_DATA_ENCIPHERMENT>, B<KU_KEY_AGREEMENT>, B<KU_KEY_CERT_SIGN>,
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B<KU_CRL_SIGN>, B<KU_ENCIPHER_ONLY> or B<KU_DECIPHER_ONLY> corresponding to
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individual key usage bits. If key usage is absent then B<UINT32_MAX> is
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returned.
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X509_get_extended_key_usage() returns the value of the extended key usage
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extension. If extended key usage is present it will return zero or more of the
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flags: B<XKU_SSL_SERVER>, B<XKU_SSL_CLIENT>, B<XKU_SMIME>, B<XKU_CODE_SIGN>
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B<XKU_OCSP_SIGN>, B<XKU_TIMESTAMP>, B<XKU_DVCS> or B<XKU_ANYEKU>. These
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correspond to the OIDs B<id-kp-serverAuth>, B<id-kp-clientAuth>,
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B<id-kp-emailProtection>, B<id-kp-codeSigning>, B<id-kp-OCSPSigning>,
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B<id-kp-timeStamping>, B<id-kp-dvcs> and B<anyExtendedKeyUsage> respectively.
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Additionally B<XKU_SGC> is set if either Netscape or Microsoft SGC OIDs are
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present.
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X509_get_extended_key_usage() return an internal pointer to the subject key
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identifier of B<x> as an B<ASN1_OCTET_STRING> or B<NULL> if the extension
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is not present or cannot be parsed.
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=head1 NOTES
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The value of the flags correspond to extension values which are cached
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in the B<X509> structure. If the flags returned do not provide sufficient
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information an application should examine extension values directly
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for example using X509_get_ext_d2i().
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If the key usage or extended key usage extension is absent then typically usage
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is unrestricted. For this reason X509_get_key_usage() and
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X509_get_extended_key_usage() return B<UINT32_MAX> when the corresponding
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extension is absent. Applications can additionally check the return value of
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X509_get_extension_flags() and take appropriate action is an extension is
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absent.
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If X509_get0_subject_key_id() returns B<NULL> then the extension may be
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absent or malformed. Applications can determine the precise reason using
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X509_get_ext_d2i().
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=head1 RETURN VALUE
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X509_get_extension_flags(), X509_get_key_usage() and
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X509_get_extended_key_usage() return sets of flags corresponding to the
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certificate extension values.
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X509_get0_subject_key_id() returns the subject key identifier as a
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pointer to an B<ASN1_OCTET_STRING> structure or B<NULL> if the extension
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is absent or an error occured during parsing.
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=head1 SEE ALSO
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L<X509_check_purpose(3)>
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=cut
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