heartbeat

Your mission

Return how many heartbeat bytes are safe to echo: honor the request only when it fits in what was actually received.

today's brief

April 2014. Heartbleed. OpenSSL's heartbeat let a client say how many bytes to echo back, and the server believed it, no questions asked. Ask for 64 kilobytes while sending almost nothing, and the reply came back padded with whatever was next in the server's memory: private keys, passwords, session cookies. Around half a million trusted web servers were exposed. The whole disaster was one missing check. Add it.

See it in action

bytes_to_echo(3, 64)

Expected result

Your checklist

For your own tracking. Tests grade your code.

requested is the number of bytes the client claims it sent; received is how many actually arrived.
If requested is between 0 and received, return requested.
If requested is negative or larger than received, the request is malformed: drop it and return 0.

More examples

bytes_to_echo(65535, 64)

Expected result

bytes_to_echo(64, 64)

Expected result

Constraints

Expected files

heartbeat.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions

heartbeat

Your mission

Return how many heartbeat bytes are safe to echo: honor the request only when it fits in what was actually received.

today's brief

See it in action

bytes_to_echo(3, 64)

Expected result

Your checklist

For your own tracking. Tests grade your code.

requested is the number of bytes the client claims it sent; received is how many actually arrived.
If requested is between 0 and received, return requested.
If requested is negative or larger than received, the request is malformed: drop it and return 0.

More examples

bytes_to_echo(65535, 64)

Expected result

bytes_to_echo(64, 64)

Expected result

Constraints

Expected files

heartbeat.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions