// SPDX-License-Identifier: GPL-2.0-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 || (a->f.flags & RBUF)) {
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,
enum op_cmp_type cmp, enum jump_type jump,
int index, struct field *f, JSON_Value *jvalue)
{
struct gluten_offset const_offset, mask_offset, data_offset;
union value v = NO_VALUE, mask = NO_VALUE;
struct gluten_offset seccomp_offset;
struct field *f_inner;
const char *tag_name;
JSON_Object *tmp;
JSON_Array *set;
JSON_Value *sel;
size_t size;
if (f->name)
debug(" parsing field name %s", f->name);
/* Some types need pre-tagging preparation */
switch (f->type) {
case GNU_DEV_MAJOR:
/*
xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
______________________ _____________
*/
v.v_num = ((long long)0xfff << 44) | (0xfff << 8);
mask_offset = emit_data(g, U64, 0, &v);
offset = emit_bitwise(g, U64, BITWISE_AND, NULL_OFFSET,
offset, mask_offset);
break;
case GNU_DEV_MINOR:
/*
xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
_____________ ________
*/
v.v_num = 0xff | ((long long)0xfff << 20);
mask_offset = emit_data(g, U64, 0, &v);
offset = emit_bitwise(g, U64, BITWISE_AND, NULL_OFFSET,
offset, mask_offset);
break;
default:
break;
}
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");
}
if (!(f->flags & FLAGS) && /* For FLAGS, it's a single operation */
json_value_get_type(jvalue) == JSONObject &&
(tmp = json_value_get_object(jvalue)) &&
(set = json_object_get_array(tmp, "in"))) {
unsigned i, count = json_array_get_count(set);
if (cmp != CMP_NE || jump != JUMP_NEXT_BLOCK)
die("unsupported nested set");
for (i = 0; i < count; i++) {
if (i == count - 1) {
cmp = CMP_NE;
jump = JUMP_NEXT_BLOCK;
} else {
cmp = CMP_EQ;
jump = JUMP_NEXT_ACTION;
}
jvalue = json_array_get_value(set, i);
parse_field(g, offset, cmp, jump, index, f, jvalue);
}
return v; /* No SELECT based on sets... of course */
}
/* Nothing to match on: just store as reference */
if (!jvalue || (f->flags & RBUF))
return v;
offset.offset += f->offset;
switch (f->type) {
case USHORT:
case INT:
case LONG:
case U32:
data_offset = offset;
if ((f->flags & FLAGS) &&
json_value_get_type(jvalue) == JSONObject &&
(tmp = json_value_get_object(jvalue))) {
struct gluten_offset set_offset, cmp_offset, masked;
union value set, cmpterm;
value_get_flags(f->desc.d_num, tmp,
&set, &cmp, &cmpterm);
set_offset = emit_data(g, f->type, 0, &set);
masked = emit_bitwise(g, f->type, BITWISE_AND,
NULL_OFFSET,
offset, set_offset);
cmp_offset = emit_data(g, f->type, 0, &cmpterm);
emit_cmp(g, cmp, masked, cmp_offset,
gluten_size[f->type], jump);
emit_bpf_arg(index, f->type, cmpterm, set, cmp);
break;
}
if (json_value_get_type(jvalue) == JSONArray) {
JSON_Array *array = json_value_get_array(jvalue);
unsigned i;
if (!(f->flags & FLAGS))
die("multiple values for non-FLAGS argument");
for (i = 0; i < json_array_get_count(array); i++) {
jvalue = json_array_get_value(array, i);
v.v_num |= value_get_num(f->desc.d_num, jvalue);
}
} else if (f->flags & MASK) {
mask.v_num = value_get_mask(f->desc.d_num);
mask_offset = emit_data(g, f->type, 0, &mask);
data_offset = emit_bitwise(g, f->type, BITWISE_AND,
NULL_OFFSET, offset,
mask_offset);
v.v_num = value_get_num(f->desc.d_num, jvalue);
} else {
v.v_num = value_get_num(f->desc.d_num, jvalue);
}
const_offset = emit_data(g, f->type, 0, &v);
emit_cmp(g, cmp, data_offset, const_offset,
gluten_size[f->type], jump);
emit_bpf_arg(index, f->type, v, mask, cmp);
break;
case GNU_DEV_MAJOR:
/*
xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
______________________ _____________
*/
v.v_num = value_get_num(f->desc.d_num, jvalue);
v.v_num = (v.v_num & 0xfff) << 8 | (v.v_num & ~0xfff) << 32;
const_offset = emit_data(g, U64, 0, &v);
emit_cmp_field(g, cmp, f, offset, const_offset, jump);
filter_needs_deref(); /* No shifts in BPF */
break;
case GNU_DEV_MINOR:
/*
xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
____________________________ ________
*/
v.v_num = value_get_num(f->desc.d_num, jvalue);
v.v_num = (v.v_num & 0xff) | (v.v_num & ~0xfff) << 12;
const_offset = emit_data(g, U64, 0, &v);
emit_cmp_field(g, cmp, f, offset, const_offset, jump);
filter_needs_deref(); /* No shifts in BPF */
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, cmp, jump, index, f_inner, sel);
f = select_field(g, index, f->desc.d_select, v);
if (f)
parse_field(g, offset, cmp, jump, 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 FDPATH:
v.v_str = json_value_get_string(jvalue);
size = strlen(v.v_str) + 1;
offset = gluten_rw_alloc(g, size);
const_offset = emit_data(g, STRING, size, &v);
seccomp_offset = emit_seccomp_data(index);
emit_resolvefd(g, seccomp_offset, offset, size);
emit_cmp(g, CMP_NE, offset, const_offset, size,
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, cmp, jump, 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, CMP_NE, JUMP_NEXT_BLOCK, 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);
filter_flush_args(call->number);
break;
}
call++;
}
if (!*set)
die(" Unknown system call: %s", name);
link_match(g);
}
link_matches(g);
}