// SPDX-License-Identifier: GPL-3.0-or-later
/* seitan - Syscall Expressive Interpreter, Transformer and Notifier
*
* cooker/match.c - Parse "match" rules from JSON recipe into bytecode
*
* Copyright 2023 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*/
#include "parson.h"
#include "calls.h"
#include "cooker.h"
#include "gluten.h"
#include "emit.h"
#include "filter.h"
#include "parse.h"
#include "util.h"
#include "calls/net.h"
/**
* arg_load() - Allocate and build bytecode for one syscall argument
* @g: gluten context
* @a: Argument description from model
*
* Return: offset where (full) argument is stored
*/
static struct gluten_offset arg_load(struct gluten_ctx *g, struct arg *a)
{
struct gluten_offset offset;
int index = a->pos;
size_t size;
if (a->f.type == SELECTED) {
if (g->selected_arg[index]->f.type != UNDEF)
size = g->selected_arg[index]->f.size;
else
die(" no storage size for argument %s", a->f.name);
} else {
size = a->f.size;
}
if (!size) {
g->match_dst[index].offset.type = OFFSET_SECCOMP_DATA;
g->match_dst[index].offset.offset = index;
g->match_dst[index].len = 0;
return g->match_dst[index].offset;
}
filter_needs_deref();
if (g->match_dst[index].len) /* Already allocated */
return g->match_dst[index].offset;
offset = gluten_rw_alloc(g, size);
g->match_dst[index].offset = offset;
g->match_dst[index].len = size;
emit_load(g, offset, index, size);
return offset;
}
/**
* parse_field() - Parse generic field along with JSON value
* @g: gluten context
* @offset: Base offset of container field (actual offset for non-compound)
* @index: Index of parent syscall argument
* @f: Field from syscall model
* @jvalue: JSON value
*
* Return: parsed value for simple types, empty value otherwise
*/
static union value parse_field(struct gluten_ctx *g,
struct gluten_offset offset,
int index, struct field *f, JSON_Value *jvalue)
{
struct gluten_offset const_offset;
union value v = { .v_num = 0 };
struct field *f_inner;
const char *tag_name;
JSON_Object *tmp;
JSON_Value *sel;
if (f->name)
debug(" parsing field name %s", f->name);
if (json_value_get_type(jvalue) == JSONObject &&
(tmp = json_value_get_object(jvalue)) &&
(tag_name = json_object_get_string(tmp, "tag"))) {
debug(" setting tag reference '%s'", tag_name);
gluten_add_tag(g, tag_name, offset);
jvalue = json_object_get_value(tmp, "value");
}
/* Nothing to match on: just store as reference */
if (!jvalue)
return v;
offset.offset += f->offset;
switch (f->type) {
case INT:
case LONG:
case U32:
if (f->flags == FLAGS) {
/* fetch/combine expr algebra loop */
;
}
if (f->flags == MASK) {
/* calculate mask first */
;
}
v.v_num = value_get_num(f->desc.d_num, jvalue);
const_offset = emit_data(g, f->type, 0, &v);
emit_cmp(g, CMP_NE, offset, const_offset, gluten_size[f->type],
JUMP_NEXT_BLOCK);
break;
case SELECT:
f_inner = f->desc.d_select->field;
if ((tmp = json_value_get_object(jvalue))) {
if (!(sel = json_object_get_value(tmp, f_inner->name)))
die(" no selector for '%s'", f_inner->name);
} else {
sel = jvalue;
}
v = parse_field(g, offset, index, f_inner, sel);
f = select_field(g, index, f->desc.d_select, v);
if (f)
parse_field(g, offset, index, f, jvalue);
break;
case STRING:
v.v_str = json_value_get_string(jvalue);
if (strlen(v.v_str) + 1 > f->size)
die(" string %s too long for field", v.v_str);
const_offset = emit_data(g, STRING, strlen(v.v_str) + 1, &v);
emit_cmp(g, CMP_NE, offset, const_offset, strlen(v.v_str) + 1,
JUMP_NEXT_BLOCK);
break;
case STRUCT:
for (f_inner = f->desc.d_struct; f_inner->name; f_inner++) {
JSON_Value *field_value;
tmp = json_value_get_object(jvalue);
field_value = json_object_get_value(tmp, f_inner->name);
if (!field_value)
continue;
parse_field(g, offset, index, f_inner, field_value);
}
break;
default:
;
}
return v;
}
/**
* parse_arg() - Parse syscall argument from JSON, following model
* @g: gluten context
* @a: Argument description from model
* @value: JSON value for argument
*/
static void parse_arg(struct gluten_ctx *g, JSON_Value *jvalue, struct arg *a)
{
struct gluten_offset offset;
debug(" Parsing match argument %s", a->f.name);
offset = arg_load(g, a);
parse_field(g, offset, a->pos, &a->f, jvalue);
}
/**
* parse_match() - Parse one "match" item in syscall rules
* @g: gluten context
* @obj: Matching rule for one syscall
* @args: Description of arguments from syscall model
*/
static void parse_match(struct gluten_ctx *g, JSON_Object *obj,
struct arg *args)
{
unsigned count = 0;
struct arg *a;
for (a = args; a->f.name; a++) {
struct arg *real_arg = a;
JSON_Value *jvalue;
if (a->f.type == SELECTED) {
if (!(real_arg = g->selected_arg[a->pos]))
die(" No argument selected for %s", a->f.name);
}
if ((jvalue = json_object_get_value(obj, real_arg->f.name))) {
count++;
parse_arg(g, jvalue, real_arg);
}
}
if (count != json_object_get_count(obj))
die(" Stray elements in match");
}
/**
* handle_matches() - Parse "match" array, find syscall models
* @g: gluten context
* @value: "match" object containing array of rules
*/
void handle_matches(struct gluten_ctx *g, JSON_Value *value)
{
JSON_Array *matches = json_value_get_array(value);
unsigned i;
for (i = 0; i < json_array_get_count(matches); i++) {
JSON_Object *match, *args;
struct call **set, *call;
const char *name;
g->mr = g->ip;
match = json_array_get_object(matches, i);
name = json_object_get_name(match, 0);
args = json_object_get_object(match, name);
debug(" Parsing match %i: %s", i, name);
for (set = call_sets, call = set[0]; *set; ) {
if (!call->name) {
set++;
call = set[0];
continue;
}
if (!strcmp(name, call->name)) {
union value v = { .v_num = call->number };
debug(" Found description for %s", name);
emit_nr(g, emit_data(g, U64, 0, &v));
filter_notify(call->number);
parse_match(g, args, call->args);
break;
}
call++;
}
if (!*set)
die(" Unknown system call: %s", name);
link_match(g);
}
}