avc_context_to_sid(3)               SE Linux API documentation              avc_context_to_sid(3)



NAME
       avc_context_to_sid,  avc_sid_to_context,  sidput,  sidget - obtain and manipulate security
       ID's.

SYNOPSIS
       #include 
       #include 

       int avc_context_to_sid(security_context_t ctx, security_id_t *sid);

       int avc_sid_to_context(security_id_t sid, security_context_t *ctx);

       int sidget(security_id_t sid);

       int sidput(security_id_t sid);

DESCRIPTION
       Security ID's (SID's) are reference-counted, opaque representations of security  contexts.

       avc_context_to_sid  returns  a  SID for the given context in the memory referenced by sid,
       incrementing its reference count by 1.

       avc_sid_to_context returns a copy of the context represented by sid in the  memory  refer-
       enced by ctx.  The user must free the copy with freecon(3).

       sidget increments the reference count of sid by 1.

       sidput  decrements  the  reference count of sid by 1.  If the count ever reaches zero, the
       SID becomes invalid and must not be used any further.


RETURN VALUE
       sidget and sidput return the new reference count.  A return value  of  zero  indicates  an
       invalid SID.

       avc_context_to_sid  and  avc_sid_to_context  return  zero  on  success.   On  error, -1 is
       returned and errno is set appropriately.


ERRORS
       EINVAL The provided sid has a zero reference count and is invalid.

       ENOMEM An attempt to allocate memory failed.


NOTES
       The expected usage pattern for these functions is that avc_context_to_sid will  be  called
       once  to  obtain a SID for a newly created object, sidget will be called on a SID when its
       object is duplicated, and sidput will be called on a SID when  its  object  is  destroyed.
       Proper  reference  counting is necessary to ensure that SID's and associated cache entries
       are reclaimed from memory when no longer needed.


AUTHOR
       Eamon Walsh <>


SEE ALSO
       avc_init(3),   avc_has_perm(3),   avc_cache_stats(3),   avc_add_callback(3),    getcon(3),
       freecon(3)



                                           27 May 2004                      avc_context_to_sid(3)