goto-fail

Repair this code

Report the first step of the chain that fails, checking every step until one does.

today's brief

February 2014. Someone duplicates one line in Apple's TLS code, a bare `goto fail;` sitting under an if that has no braces. It always jumps, so the signature check underneath it never runs, and every iPhone and Mac happily accepts forged certificates on any network. The line had been shipping for over a year. Here is the same shape: a chain of checks where only the first one ever happens.

See it in action

first_bad_step({1,1,1}, 3)

Expected result

-1

Your checklist

For your own tracking. Tests grade your code.

step_ok holds n check results in order, 1 for a step that passed and 0 for a step that failed.
Return the index of the first step that failed.
Return -1 when every step passed, and when there is no step at all.

More examples

first_bad_step({1,0,1}, 3)

Expected result

first_bad_step({0,0,0}, 3)

Expected result

Constraints

Expected files

verify.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions

goto-fail

Repair this code

Report the first step of the chain that fails, checking every step until one does.

today's brief

See it in action

first_bad_step({1,1,1}, 3)

Expected result

-1

Your checklist

For your own tracking. Tests grade your code.

step_ok holds n check results in order, 1 for a step that passed and 0 for a step that failed.
Return the index of the first step that failed.
Return -1 when every step passed, and when there is no step at all.

More examples

first_bad_step({1,0,1}, 3)

Expected result

first_bad_step({0,0,0}, 3)

Expected result

Constraints

Expected files

verify.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions