Ubuntu Manpage: gnutls_priority_init

Provided by: gnutls-doc_3.5.18-1ubuntu1.6_all

NAME

       gnutls_priority_init - API function

SYNOPSIS

       #include <gnutls/gnutls.h>

       int  gnutls_priority_init(gnutls_priority_t  *  priority_cache,  const  char * priorities,
       const char ** err_pos);

ARGUMENTS

       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

DESCRIPTION

Sets priorities for the ciphers, key exchange methods, macs and compression methods. 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.

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 even protocols and compression methods.

"@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 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:+COMP-DEFLATE"  means that only secure ciphers are enabled, SSL3.0
       is disabled, and libz compression enabled.

       "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.

REPORTING BUGS

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

COPYRIGHT

       Copyright © 2001-2022 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.