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lib: check frame_size is >= INT32_MAX

When parsing a frame header, validate that the frame_size is less than
or equal to INT32_MAX. Given frame_max is limited between 0 and
INT32_MAX in amqp_login and friends, this does not change the API.

This prevents a potential buffer overflow when a malicious client sends
a frame_size that is close to UINT32_MAX, in which causes an overflow
when computing state->target_size resulting in a small value there. A
buffer is then allocated with the small amount, then memcopy copies the
frame_size writing to memory beyond the end of the buffer.
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alanxz committed Nov 4, 2019
1 parent 60adf5f commit fc85be7123050b91b054e45b91c78d3241a5047a
Showing with 12 additions and 3 deletions.
  1. +12 −3 librabbitmq/amqp_connection.c
@@ -287,12 +287,21 @@ int amqp_handle_input(amqp_connection_state_t state, amqp_bytes_t received_data,
case CONNECTION_STATE_HEADER: {
amqp_channel_t channel;
amqp_pool_t *channel_pool;
/* frame length is 3 bytes in */
uint32_t frame_size;

channel = amqp_d16(amqp_offset(raw_frame, 1));

state->target_size =
amqp_d32(amqp_offset(raw_frame, 3)) + HEADER_SIZE + FOOTER_SIZE;
/* frame length is 3 bytes in */
frame_size = amqp_d32(amqp_offset(raw_frame, 3));
/* To prevent the target_size calculation below from overflowing, check
* that the stated frame_size is smaller than a signed 32-bit. Given
* the library only allows configuring frame_max as an int32_t, and
* frame_size is uint32_t, the math below is safe from overflow. */
if (frame_size >= INT32_MAX) {
return AMQP_STATUS_BAD_AMQP_DATA;
}

state->target_size = frame_size + HEADER_SIZE + FOOTER_SIZE;
if ((size_t)state->frame_max < state->target_size) {
return AMQP_STATUS_BAD_AMQP_DATA;
}

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