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       X509_LOOKUP_hash_dir, X509_LOOKUP_file, X509_load_cert_file, X509_load_crl_file,
       X509_load_cert_crl_file - Default OpenSSL certificate lookup methods


        #include <openssl/x509_vfy.h>

        X509_LOOKUP_METHOD *X509_LOOKUP_hash_dir(void);
        X509_LOOKUP_METHOD *X509_LOOKUP_file(void);

        int X509_load_cert_file(X509_LOOKUP *ctx, const char *file, int type);
        int X509_load_crl_file(X509_LOOKUP *ctx, const char *file, int type);
        int X509_load_cert_crl_file(X509_LOOKUP *ctx, const char *file, int type);


       X509_LOOKUP_hash_dir and X509_LOOKUP_file are two certificate lookup methods to use with
       X509_STORE, provided by OpenSSL library.

       Users of the library typically do not need to create instances of these methods manually,
       they would be created automatically by X509_STORE_load_locations(3) or
       SSL_CTX_load_verify_locations(3) functions.

       Internally loading of certificates and CRLs is implemented via functions
       X509_load_cert_crl_file, X509_load_cert_file and X509_load_crl_file. These functions
       support parameter type, which can be one of constants FILETYPE_PEM, FILETYPE_ASN1 and
       FILETYPE_DEFAULT. They load certificates and/or CRLs from specified file into memory cache
       of X509_STORE objects which given ctx parameter is associated with.

       Functions X509_load_cert_file and X509_load_crl_file can load both PEM and DER formats
       depending of type value. Because DER format cannot contain more than one certificate or
       CRL object (while PEM can contain several concatenated PEM objects)
       X509_load_cert_crl_file with FILETYPE_ASN1 is equivalent to X509_load_cert_file.

       Constant FILETYPE_DEFAULT with NULL filename causes these functions to load default
       certificate store file (see X509_STORE_set_default_paths(3).

       Functions return number of objects loaded from file or 0 in case of error.

       Both methods support adding several certificate locations into one X509_STORE.

       This page documents certificate store formats used by these methods and caching policy.

   File Method
       The X509_LOOKUP_file method loads all the certificates or CRLs present in a file into
       memory at the time the file is added as a lookup source.

       File format is ASCII text which contains concatenated PEM certificates and CRLs.

       This method should be used by applications which work with a small set of CAs.

   Hashed Directory Method
       X509_LOOKUP_hash_dir is a more advanced method, which loads certificates and CRLs on
       demand, and caches them in memory once they are loaded. As of OpenSSL 1.0.0, it also
       checks for newer CRLs upon each lookup, so that newer CRLs are as soon as they appear in
       the directory.

       The directory should contain one certificate or CRL per file in PEM format, with a file
       name of the form hash.N for a certificate, or hash.rN for a CRL.  The hash is the value
       returned by the X509_NAME_hash(3) function applied to the subject name for certificates or
       issuer name for CRLs.  The hash can also be obtained via the -hash option of the x509(1)
       or crl(1) commands.

       The .N or .rN suffix is a sequence number that starts at zero, and is incremented
       consecutively for each certificate or CRL with the same hash value.  Gaps in the sequence
       numbers are not supported, it is assumed that there are no more objects with the same hash
       beyond the first missing number in the sequence.

       Sequence numbers make it possible for the directory to contain multiple certificates with
       same subject name hash value.  For example, it is possible to have in the store several
       certificates with same subject or several CRLs with same issuer (and, for example,
       different validity period).

       When checking for new CRLs once one CRL for given hash value is loaded, hash_dir lookup
       method checks only for certificates with sequence number greater than that of the already
       cached CRL.

       Note that the hash algorithm used for subject name hashing changed in OpenSSL 1.0.0, and
       all certificate stores have to be rehashed when moving from OpenSSL 0.9.8 to 1.0.0.

       OpenSSL includes a rehash(1) utility which creates symlinks with correct hashed names for
       all files with .pem suffix in a given directory.


       X509_LOOKUP_hash_dir() and X509_LOOKUP_file() always return a valid X509_LOOKUP_METHOD

       X509_load_cert_file(), X509_load_crl_file() and X509_load_cert_crl_file() return the
       number of loaded objects or 0 on error.


       PEM_read_PrivateKey(3), X509_STORE_load_locations(3), X509_store_add_lookup(3),
       SSL_CTX_load_verify_locations(3), X509_LOOKUP_meth_new(3),


       Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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 <>.