c_rehash

REHASH(1SSL)                        OpenSSL                       REHASH(1SSL)

NAME
       openssl-c_rehash, openssl-rehash, c_rehash, rehash - Create symbolic
       links to files named by the hash values

SYNOPSIS
       openssl rehash [-h] [-help] [-old] [-n] [-v] [ directory...]

       c_rehash flags...

DESCRIPTION
       On some platforms, the OpenSSL rehash command is available as an
       external script called c_rehash.  They are functionally equivalent,
       except for minor differences noted below.

       rehash scans directories and calculates a hash value of each ".pem",
       ".crt", ".cer", or ".crl" file in the specified directory list and
       creates symbolic links for each file, where the name of the link is the
       hash value.  (If the platform does not support symbolic links, a copy
       is made.)  This utility is useful as many programs that use OpenSSL
       require directories to be set up like this in order to find
       certificates.

       If any directories are named on the command line, then those are
       processed in turn. If not, then the SSL_CERT_DIR environment variable
       is consulted; this should be a colon-separated list of directories,
       like the Unix PATH variable.  If that is not set then the default
       directory (installation-specific but often /usr/local/ssl/certs) is
       processed.

       In order for a directory to be processed, the user must have write
       permissions on that directory, otherwise an error will be generated.

       The links created are of the form "HHHHHHHH.D", where each H is a
       hexadecimal character and D is a single decimal digit.  When processing
       a directory, rehash will first remove all links that have a name in
       that syntax, even if they are being used for some other purpose.  To
       skip the removal step, use the -n flag.  Hashes for CRL's look similar
       except the letter r appears after the period, like this: "HHHHHHHH.rD".

       Multiple objects may have the same hash; they will be indicated by
       incrementing the D value. Duplicates are found by comparing the full
       SHA-1 fingerprint. A warning will be displayed if a duplicate is found.

       A warning will also be displayed if there are files that cannot be
       parsed as either a certificate or a CRL or if more than one such object
       appears in the file.

   Script Configuration
       The c_rehash script uses the openssl program to compute the hashes and
       fingerprints. If not found in the user's PATH, then set the OPENSSL
       environment variable to the full pathname.  Any program can be used, it
       will be invoked as follows for either a certificate or CRL:

         $OPENSSL x509 -hash -fingerprint -noout -in FILENAME
         $OPENSSL crl -hash -fingerprint -noout -in FILENAME

       where FILENAME is the filename. It must output the hash of the file on
       the first line, and the fingerprint on the second, optionally prefixed
       with some text and an equals sign.

OPTIONS
       -help -h
           Display a brief usage message.

       -old
           Use old-style hashing (MD5, as opposed to SHA-1) for generating
           links to be used for releases before 1.0.0.  Note that current
           versions will not use the old style.

       -n  Do not remove existing links.  This is needed when keeping new and
           old-style links in the same directory.

       -compat
           Generate links for both old-style (MD5) and new-style (SHA1)
           hashing.  This allows releases before 1.0.0 to use these links
           along-side newer releases.

       -v  Print messages about old links removed and new links created.  By
           default, rehash only lists each directory as it is processed.

ENVIRONMENT
       OPENSSL
           The path to an executable to use to generate hashes and
           fingerprints (see above).

       SSL_CERT_DIR
           Colon separated list of directories to operate on.  Ignored if
           directories are listed on the command line.

SEE ALSO
       openssl(1), crl(1).  x509(1).

COPYRIGHT
       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
       <https://www.openssl.org/source/license.html>.

1.1.1f                            2023-10-10                      REHASH(1SSL)