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validate props, fuzz them

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Sergio R. Caprile committed 2026-02-06 10:53:25 -03:00
1 parent 70d268d95f
commit 2d7e8aa712
3 files changed
+38 -6
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mongoose.c
+15 -3
View File
@@ -4113,47 +4113,59 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
size_t new_pos = ofs, len;
prop->id = i[0];
if (ofs >= msg->dgram.len || ofs >= msg->props_start + msg->props_size)
if (ofs >= msg->dgram.len || ofs >= msg->props_start + msg->props_size || (i + 1) >= end)
return 0;
i++, new_pos++;
switch (mqtt_prop_type_by_id(prop->id)) {
case MQTT_PROP_TYPE_STRING_PAIR:
if (i + 2 >= end) return 0;
prop->key.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->key.buf = (char *) i + 2;
i += 2 + prop->key.len;
if (i + 2 >= end) return 0;
prop->val.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->val.buf = (char *) i + 2;
if (i + 2 + prop->val.len > end) return 0;
new_pos += 2 * sizeof(uint16_t) + prop->val.len + prop->key.len;
break;
case MQTT_PROP_TYPE_BYTE:
if (i + 1 > end) return 0;
prop->iv = (uint8_t) i[0];
new_pos++;
break;
case MQTT_PROP_TYPE_SHORT:
if (i + 2 > end) return 0;
prop->iv = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
new_pos += sizeof(uint16_t);
break;
case MQTT_PROP_TYPE_INT:
if (i + 4 > end) return 0;
prop->iv = ((uint32_t) i[0] << 24) | ((uint32_t) i[1] << 16) |
((uint32_t) i[2] << 8) | i[3];
new_pos += sizeof(uint32_t);
break;
case MQTT_PROP_TYPE_STRING:
if (i + 2 >= end) return 0;
prop->val.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->val.buf = (char *) i + 2;
if (i + 2 + prop->val.len > end) return 0;
new_pos += 2 + prop->val.len;
break;
case MQTT_PROP_TYPE_BINARY_DATA:
if (i + 2 > end) return 0;
prop->val.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->val.buf = (char *) i + 2;
new_pos += 2 + prop->val.len;
break;
case MQTT_PROP_TYPE_VARIABLE_INT:
len = decode_varint(i, (size_t) (end - i), (size_t *) &prop->iv);
new_pos = (!len) ? 0 : new_pos + len;
if (i + len > end) return 0;
new_pos = (len == 0) ? 0 : new_pos + len;
break;
default:
new_pos = 0;
break;
default: new_pos = 0;
}
return new_pos;
src/mqtt.c
+15 -3
View File
@@ -208,47 +208,59 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
size_t new_pos = ofs, len;
prop->id = i[0];
if (ofs >= msg->dgram.len || ofs >= msg->props_start + msg->props_size)
if (ofs >= msg->dgram.len || ofs >= msg->props_start + msg->props_size || (i + 1) >= end)
return 0;
i++, new_pos++;
switch (mqtt_prop_type_by_id(prop->id)) {
case MQTT_PROP_TYPE_STRING_PAIR:
if (i + 2 >= end) return 0;
prop->key.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->key.buf = (char *) i + 2;
i += 2 + prop->key.len;
if (i + 2 >= end) return 0;
prop->val.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->val.buf = (char *) i + 2;
if (i + 2 + prop->val.len > end) return 0;
new_pos += 2 * sizeof(uint16_t) + prop->val.len + prop->key.len;
break;
case MQTT_PROP_TYPE_BYTE:
if (i + 1 > end) return 0;
prop->iv = (uint8_t) i[0];
new_pos++;
break;
case MQTT_PROP_TYPE_SHORT:
if (i + 2 > end) return 0;
prop->iv = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
new_pos += sizeof(uint16_t);
break;
case MQTT_PROP_TYPE_INT:
if (i + 4 > end) return 0;
prop->iv = ((uint32_t) i[0] << 24) | ((uint32_t) i[1] << 16) |
((uint32_t) i[2] << 8) | i[3];
new_pos += sizeof(uint32_t);
break;
case MQTT_PROP_TYPE_STRING:
if (i + 2 >= end) return 0;
prop->val.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->val.buf = (char *) i + 2;
if (i + 2 + prop->val.len > end) return 0;
new_pos += 2 + prop->val.len;
break;
case MQTT_PROP_TYPE_BINARY_DATA:
if (i + 2 > end) return 0;
prop->val.len = (uint16_t) ((((uint16_t) i[0]) << 8) | i[1]);
prop->val.buf = (char *) i + 2;
new_pos += 2 + prop->val.len;
break;
case MQTT_PROP_TYPE_VARIABLE_INT:
len = decode_varint(i, (size_t) (end - i), (size_t *) &prop->iv);
new_pos = (!len) ? 0 : new_pos + len;
if (i + len > end) return 0;
new_pos = (len == 0) ? 0 : new_pos + len;
break;
default:
new_pos = 0;
break;
default: new_pos = 0;
}
return new_pos;
test/fuzz.c
+8
View File
@@ -62,6 +62,14 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
mg_crc32(0, mm.topic.buf, mm.topic.len);
mg_crc32(0, mm.data.buf, mm.data.len);
mg_crc32(0, mm.dgram.buf, mm.dgram.len);
{
struct mg_mqtt_prop prop;
size_t ofs = 0;
while ((ofs = mg_mqtt_next_prop(&mm, &prop, ofs)) > 0) {
mg_crc32(0, prop.key.buf, prop.key.len);
mg_crc32(0, prop.val.buf, prop.val.len);
}
}
}
mg_mqtt_parse(NULL, 0, 5, &mm);