NAME

       seccomp_attr_set, seccomp_attr_get - Manage the seccomp filter attributes

SYNOPSIS

       #include <seccomp.h>

       typedef void * scmp_filter_ctx;
       enum scmp_filter_attr;

       int seccomp_attr_set(scmp_filter_ctx ctx,
                            enum scmp_filter_attr attr, uint32_t value);
       int seccomp_attr_get(scmp_filter_ctx ctx,
                            enum scmp_filter_attr attr, uint32_t *value);

       Link with -lseccomp.

DESCRIPTION

       The seccomp_attr_set() function sets the different seccomp filter attributes while the seccomp_attr_get()
       function fetches the filter attributes.  The seccomp filter attributes are tunable values that affect how
       the  library  behaves when generating and loading the seccomp filter into the kernel.  The attributes are
       reset to their default values whenever the filter is initialized or reset via  seccomp_filter_init(3)  or
       seccomp_filter_reset(3).

       The filter context ctx is the value returned by the call to seccomp_init(3).

       Valid attr values are as follows:

       SCMP_FLTATR_ACT_DEFAULT
              The   default   filter   action   as   specified   in   the   call  to  seccomp_filter_init(3)  or
              seccomp_filter_reset(3).  This attribute is read-only.

       SCMP_FLTATR_ACT_BADARCH
              The filter action taken when the loaded filter does not match the architecture  of  the  executing
              application.  Defaults to the SCMP_ACT_KILL action.

       SCMP_FLTATR_CTL_NNP
              A  flag  to specify if the NO_NEW_PRIVS functionality should be enabled before loading the seccomp
              filter into the kernel.  Setting this to off ( value == 0) results  in  no  action,  meaning  that
              loading  the seccomp filter into the kernel will fail if CAP_SYS_ADMIN is missing and NO_NEW_PRIVS
              has not been externally set.  Defaults to on ( value == 1).

       SCMP_FLTATR_CTL_TSYNC
              A flag to specify if the kernel should attempt to synchronize the filters across  all  threads  on
              seccomp_load(3).  If the kernel is unable to synchronize all of the thread then the load operation
              will fail.  This flag is only available on Linux Kernel 3.17 or greater; attempting to enable this
              flag on earlier kernels will result in an error being returned.  Defaults to off ( value == 0).

       SCMP_FLTATR_API_TSKIP
              A  flag  to specify if libseccomp should allow filter rules to be created for the -1 syscall.  The
              -1 syscall value can be used  by  tracer  programs  to  skip  specific  syscall  invocations,  see
              seccomp(2) for more information.  Defaults to off ( value == 0).

       SCMP_FLTATR_CTL_LOG
              A  flag to specify if the kernel should log all filter actions taken except for the SCMP_ACT_ALLOW
              action. Defaults to off ( value == 0).

       SCMP_FLTATR_CTL_SSB
              A flag to disable Speculative Store Bypass mitigations for this filter.  Defaults to off  (  value
              == 0).

       SCMP_FLTATR_CTL_OPTIMIZE
              A flag to specify the optimization level of the seccomp filter.  By default libseccomp generates a
              set of sequential ´if´ statements for each rule in the filter.  seccomp_syscall_priority(3) can be
              used to prioritize the order for the default cause.  The binary tree optimization sorts by syscall
              numbers and generates consistent O(log n) filter traversal for every  rule  in  the  filter.   The
              binary  tree  may  be  advantageous  for  large filters.  Note that seccomp_syscall_priority(3) is
              ignored when SCMP_FLTATR_CTL_OPTIMIZE == 2.

              The different optimization levels are described below:

              0      Reserved value, not currently used.

              1      Rules sorted by priority and complexity (DEFAULT).

              2      Binary tree sorted by syscall number.

       SCMP_FLTATR_API_SYSRAWRC
              A flag to specify if libseccomp should pass system error codes back to the caller instead  of  the
              default -ECANCELED.  Defaults to off ( value == 0).

RETURN VALUE

       Returns zero on success or one of the following error codes on failure:

       -EACCES
              Setting the attribute with the given value is not allowed.

       -EEXIST
              The attribute does not exist.

       -EINVAL
              Invalid input, either the context or architecture token is invalid.

       -EOPNOTSUPP
              The library doesn't support the particular operation.

EXAMPLES

       #include <seccomp.h>

       int main(int argc, char *argv[])
       {
            int rc = -1;
            scmp_filter_ctx ctx;

            ctx = seccomp_init(SCMP_ACT_ALLOW);
            if (ctx == NULL)
                 goto out;

            /* ... */

            rc = seccomp_attr_set(ctx, SCMP_FLTATR_ACT_BADARCH, SCMP_ACT_TRAP);
            if (rc < 0)
                 goto out;

            /* ... */

       out:
            seccomp_release(ctx);
            return -rc;
       }

NOTES

       While  the  seccomp filter can be generated independent of the kernel, kernel support is required to load
       and enforce the seccomp filter generated by libseccomp.

       The libseccomp project site, with more information and the  source  code  repository,  can  be  found  at
       https://github.com/seccomp/libseccomp.   This tool, as well as the libseccomp library, is currently under
       development, please report any bugs at the project site or directly to the author.

AUTHOR

       Paul Moore <paul@paul-moore.com>

SEE ALSO

       seccomp_init(3), seccomp_reset(3), seccomp_load(3), seccomp(2)