The archive at http://trust-in-soft.com/x509_certs.tgz provides ~500 files that can be used as inputs of a command such as the following:
src/asn1Decoding tests/pkix.asn @@ PKIX1.Certificate @@ is the name of one of the files. These files between themselves cover many behaviors of asn1Decoding in a minimum of time. The error behaviors will be particularly well covered but it is not excluded that a couple of the files are valid certificates or undistinguishable from them. The files were generated with afl: http://lcamtuf.coredump.cx/afl/ using seeds contributed by Miod Vallat.
