gnutls_priority_init2(3) — Linux manual page


gnutls_priority_init2(3)           gnutls           gnutls_priority_init2(3)

NAME         top

       gnutls_priority_init2 - API function

SYNOPSIS         top

       #include <gnutls/gnutls.h>

       int gnutls_priority_init2(gnutls_priority_t * priority_cache, const
       char * priorities, const char ** err_pos, unsigned flags);

ARGUMENTS         top

       gnutls_priority_t * priority_cache
                   is a gnutls_prioritity_t type.

       const char * priorities
                   is a string describing priorities (may be NULL)

       const char ** err_pos
                   In case of an error this will have the position in the
                   string the error occurred

       unsigned flags
                   zero or GNUTLS_PRIORITY_INIT_DEF_APPEND

DESCRIPTION         top

       Sets priorities for the ciphers, key exchange methods, and macs.  The
       priority_cache should be deinitialized using

       The priorities option allows you to specify a colon separated list of
       the cipher priorities to enable.  Some keywords are defined to
       provide quick access to common preferences.

       When  flags is set to GNUTLS_PRIORITY_INIT_DEF_APPEND then the
       priorities specified will be appended to the default options.

       Unless there is a special need, use the "NORMAL" keyword to apply a
       reasonable security level, or "NORMAL:%COMPAT" for compatibility.

       "PERFORMANCE" means all the "secure" ciphersuites are enabled,
       limited to 128 bit ciphers and sorted by terms of speed performance.

       "LEGACY" the NORMAL settings for GnuTLS 3.2.x or earlier. There is no
       verification profile set, and the allowed DH primes are considered
       weak today.

       "NORMAL" means all "secure" ciphersuites. The 256-bit ciphers are
       included as a fallback only.  The ciphers are sorted by security

       "PFS" means all "secure" ciphersuites that support perfect forward
       secrecy.  The 256-bit ciphers are included as a fallback only.  The
       ciphers are sorted by security margin.

       "SECURE128" means all "secure" ciphersuites of security level 128-bit
       or more.

       "SECURE192" means all "secure" ciphersuites of security level 192-bit
       or more.

       "SUITEB128" means all the NSA SuiteB ciphersuites with security level
       of 128.

       "SUITEB192" means all the NSA SuiteB ciphersuites with security level
       of 192.

       "NONE" means nothing is enabled.  This disables everything, including

       "@KEYWORD1,KEYWORD2,..." The system administrator imposed settings.
       The provided keyword(s) will be expanded from a configuration-time
       provided file - default is: /etc/gnutls/default-priorities.  Any
       attributes that follow it, will be appended to the expanded string.
       If multiple keywords are provided, separated by commas, then the
       first keyword that exists in the configuration file will be used. At
       least one of the keywords must exist, or this function will return an
       error. Typical usage would be to specify an application specified
       keyword first, followed by "SYSTEM" as a default fallback. e.g., "
       LIBVIRT ,SYSTEM:!-VERS-SSL3.0" will first try to find a config file
       entry matching "LIBVIRT", but if that does not exist will use the
       entry for "SYSTEM". If "SYSTEM" does not exist either, an error will
       be returned. In all cases, the SSL3.0 protocol will be disabled. The
       system priority file entries should be formatted as "KEYWORD=VALUE",
       e.g., "SYSTEM=NORMAL:+ARCFOUR-128".

       Special keywords are "!", "-" and "+".  "!" or "-" appended with an
       algorithm will remove this algorithm.  "+" appended with an algorithm
       will add this algorithm.

       Check the GnuTLS manual section "Priority strings" for detailed

EXAMPLES         top


       "NORMAL:+ARCFOUR-128" means normal ciphers plus ARCFOUR-128.

       "SECURE128:-VERS-SSL3.0" means that only secure ciphers are and
       enabled, SSL3.0 is disabled.




       Note that "NORMAL:%COMPAT" is the most compatible mode.

       A NULL  priorities string indicates the default priorities to be used
       (this is available since GnuTLS 3.3.0).

RETURNS         top

       On syntax error GNUTLS_E_INVALID_REQUEST is returned,
       GNUTLS_E_SUCCESS on success, or an error code.

SINCE         top


REPORTING BUGS         top

       Report bugs to <>.
       Home page:

COPYRIGHT         top

       Copyright © 2001-2019 Free Software Foundation, Inc., and others.
       Copying and distribution of this file, with or without modification,
       are permitted in any medium without royalty provided the copyright
       notice and this notice are preserved.

SEE ALSO         top

       The full documentation for gnutls is maintained as a Texinfo manual.
       If the /usr/share/doc/gnutls/ directory does not contain the HTML
       form visit 

COLOPHON         top

       This page is part of the GnuTLS (GnuTLS Transport Layer Security
       Library) project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       tarball gnutls-3.6.9.tar.xz fetched from
       ⟨⟩ on 2020-09-18.  If you discover
       any rendering problems in this HTML version of the page, or you
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gnutls                              3.6.9           gnutls_priority_init2(3)