NAME

       X509_digest, X509_digest_sig, X509_CRL_digest, X509_pubkey_digest, X509_NAME_digest,
       X509_REQ_digest, PKCS7_ISSUER_AND_SERIAL_digest - get digest of various objects

SYNOPSIS

        #include <openssl/x509.h>

        int X509_digest(const X509 *data, const EVP_MD *type, unsigned char *md,
                        unsigned int *len);
        ASN1_OCTET_STRING *X509_digest_sig(const X509 *cert,
                                           EVP_MD **md_used, int *md_is_fallback);

        int X509_CRL_digest(const X509_CRL *data, const EVP_MD *type, unsigned char *md,
                            unsigned int *len);

        int X509_pubkey_digest(const X509 *data, const EVP_MD *type,
                               unsigned char *md, unsigned int *len);

        int X509_REQ_digest(const X509_REQ *data, const EVP_MD *type,
                            unsigned char *md, unsigned int *len);

        int X509_NAME_digest(const X509_NAME *data, const EVP_MD *type,
                             unsigned char *md, unsigned int *len);

        #include <openssl/pkcs7.h>

        int PKCS7_ISSUER_AND_SERIAL_digest(PKCS7_ISSUER_AND_SERIAL *data,
                                           const EVP_MD *type, unsigned char *md,
                                           unsigned int *len);

DESCRIPTION

       X509_digest_sig() calculates a digest of the given certificate cert using the same hash
       algorithm as in its signature, if the digest is an integral part of the certificate
       signature algorithm identifier.  Otherwise, a fallback hash algorithm is determined as
       follows: SHA512 if the signature alorithm is ED25519, SHAKE256 if it is ED448, otherwise
       SHA256.  The output parmeters are assigned as follows.  Unless md_used is NULL, the hash
       algorithm used is provided in *md_used and must be freed by the caller (if it is not
       NULL).  Unless md_is_fallback is NULL, the *md_is_fallback is set to 1 if the hash
       algorithm used is a fallback, otherwise to 0.

       X509_pubkey_digest() returns a digest of the DER representation of the public key in the
       specified X509 data object.

       All other functions described here return a digest of the DER representation of their
       entire data objects.

       The type parameter specifies the digest to be used, such as EVP_sha1(). The md is a
       pointer to the buffer where the digest will be copied and is assumed to be large enough;
       the constant EVP_MAX_MD_SIZE is suggested. The len parameter, if not NULL, points to a
       place where the digest size will be stored.

RETURN VALUES

       X509_digest_sig() returns an ASN1_OCTET_STRING pointer on success, else NULL.

       All other functions described here return 1 for success and 0 for failure.

SEE ALSO

       EVP_sha1(3)

HISTORY

       The X509_digest_sig() function was added in OpenSSL 3.0.

COPYRIGHT

       Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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 <https://www.openssl.org/source/license.html>.