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Merged
robertc2000 merged 1 commit into from
Feb 9, 2026
Merged

Improve mqtt props bound checks #3435

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19 changes: 11 additions & 8 deletions mongoose.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4111,10 +4111,12 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
uint8_t *i = (uint8_t *) msg->dgram.buf + msg->props_start + ofs;
uint8_t *end = (uint8_t *) msg->dgram.buf + msg->dgram.len;
size_t new_pos = ofs, len;
prop->id = i[0];

if (ofs >= msg->dgram.len || ofs >= msg->props_start + msg->props_size || (i + 1) >= end)
return 0;

memset(prop, 0, sizeof(struct mg_mqtt_prop));
prop->id = i[0];
i++, new_pos++;

switch (mqtt_prop_type_by_id(prop->id)) {
Expand All @@ -4126,21 +4128,21 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
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;
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;
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;
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;
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);
Expand All @@ -4149,18 +4151,19 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
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;
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;
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_VARIABLE_INT:
len = decode_varint(i, (size_t) (end - i), (size_t *) &prop->iv);
if (i + len > end) return 0;
if (i + len >= end) return 0;
new_pos = (len == 0) ? 0 : new_pos + len;
break;
default:
Expand Down
19 changes: 11 additions & 8 deletions src/mqtt.c
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -206,10 +206,12 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
uint8_t *i = (uint8_t *) msg->dgram.buf + msg->props_start + ofs;
uint8_t *end = (uint8_t *) msg->dgram.buf + msg->dgram.len;
size_t new_pos = ofs, len;
prop->id = i[0];

if (ofs >= msg->dgram.len || ofs >= msg->props_start + msg->props_size || (i + 1) >= end)
return 0;

memset(prop, 0, sizeof(struct mg_mqtt_prop));
prop->id = i[0];
i++, new_pos++;

switch (mqtt_prop_type_by_id(prop->id)) {
Expand All @@ -221,21 +223,21 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
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;
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;
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;
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;
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);
Expand All @@ -244,18 +246,19 @@ size_t mg_mqtt_next_prop(struct mg_mqtt_message *msg, struct mg_mqtt_prop *prop,
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;
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;
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_VARIABLE_INT:
len = decode_varint(i, (size_t) (end - i), (size_t *) &prop->iv);
if (i + len > end) return 0;
if (i + len >= end) return 0;
new_pos = (len == 0) ? 0 : new_pos + len;
break;
default:
Expand Down
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