lets-encrypt

Your mission

Copy a certificate chain into out with its last link removed.

today's brief

September 30, 2021. The DST Root CA X3 certificate expires just after two in the afternoon and takes a slice of the web down with it. Let's Encrypt had been cross signing to that ancient root so old Android phones would keep trusting them, and software that insisted on walking a chain all the way to the top now walked straight into an expired certificate and refused perfectly valid sites. The fix on the server side was to stop sending the last link. Cut the chain short.

See it in action

short_chain(out, "leaf>R3>DST")

Expected result

leaf>R3

Your checklist

For your own tracking. Tests grade your code.

chain holds certificate names separated by >, and out has room for the whole string.
Copy chain into out without its last name and without the > in front of that name.
A chain with no > in it leaves out empty.
Terminate out with a zero byte.

More examples

short_chain(out, "leaf>R3")

Expected result

leaf

short_chain(out, "leaf")

Expected result

(empty result)

Constraints

Expected files

chain.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions

lets-encrypt

Your mission

Copy a certificate chain into out with its last link removed.

today's brief

See it in action

short_chain(out, "leaf>R3>DST")

Expected result

leaf>R3

Your checklist

For your own tracking. Tests grade your code.

chain holds certificate names separated by >, and out has room for the whole string.
Copy chain into out without its last name and without the > in front of that name.
A chain with no > in it leaves out empty.
Terminate out with a zero byte.

More examples

short_chain(out, "leaf>R3")

Expected result

leaf

short_chain(out, "leaf")

Expected result

(empty result)

Constraints

Expected files

chain.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions