Ubuntu Manpage: gnutls_priority_init2

Provided by: gnutls-doc_3.8.3-1.1ubuntu3.4_all

NAME

       gnutls_priority_init2 - API function

SYNOPSIS

       #include <gnutls/gnutls.h>

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

ARGUMENTS

       gnutls_priority_t * priority_cache
                   is a gnutls_priority_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

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

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 margin.

"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 protocols.

"@KEYWORD1,KEYWORD2,..." The system administrator imposed settings. The provided keyword(s) will be
expanded from a configuration-time provided file - default is: /etc/gnutls/config. 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 information.

EXAMPLES

       "NONE:+VERS-TLS-ALL:+MAC-ALL:+RSA:+AES-128-CBC:+SIGN-ALL:+COMP-NULL"

       "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.

       "NONE:+VERS-TLS-ALL:+AES-128-CBC:+RSA:+SHA1:+COMP-NULL:+SIGN-RSA-SHA1",

       "NONE:+VERS-TLS-ALL:+AES-128-CBC:+ECDHE-RSA:+SHA1:+COMP-NULL:+SIGN-RSA-SHA1:+CURVE-SECP256R1",

       "SECURE256:+SECURE128",

       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

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

SINCE

       3.6.3

REPORTING BUGS

       Report bugs to <bugs@gnutls.org>.
       Home page: https://www.gnutls.org

COPYRIGHT

       Copyright © 2001-2023 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.