c_rehash(1)

NAME

       c_rehash - Create symbolic links to files named by the hash values

SYNOPSIS

       c_rehash [-old] [-h] [-n] [-v] [ directory...]

DESCRIPTION

       c_rehash scans directories and calculates a hash value of each ".pem",
       ".crt", ".cer", or ".crl" file in the specified directory list and cre-
       ates 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 certifi-
       cates.

       If any directories are named on the command line, then those are pro-
       cessed in turn. If not, then the SSL_CERT_DIR environment variable is
       consulted; this shold 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 per-
       missions on that directory, otherwise it will be skipped.  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 direc-
       tory, c_rehash will first remove all links that have a name in that
       syntax. If you have links in that format used for other purposes, they
       will be removed.  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.

       The program uses the openssl program to compute the hashes and finger-
       prints. If not found in the user's PATH, then set the OPENSSL environ-
       ment 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

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

       -h  Display a brief usage message.

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

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

ENVIRONMENT

       OPENSSL
           The path to an executable to use to generate hashes and finger-
           prints (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).

1.0.2t                            2019-09-10                       C_REHASH(1)