KEYS: Provide a script to extract a module signature
The supplied script takes a signed module file and extracts the tailmost
signature (there could theoretically be more than one) and dumps all or
part of it or the unsigned file to stdout.
scripts/extract-module-sig.pl -[0adnks] module-file >out
where the initial flag indicates which bit of the signed file you want dumping
(*) "-0". Dumps the unsigned data with the signature stripped.
(*) "-a". Dumps all of the signature data, including the magic number.
(*) "-d". Dumps the signature information block as a sequence of decimal
numbers in text form with spaces between (crypto algorithm type,
hash type, identifier type, signer's name length, key identifier
length and signature length).
(*) "-n". Dumps the signer's name contents.
(*) "-k". Dumps the key identifier contents.
(*) "-s". Dumps the cryptographic signature contents.
In the case that the signature is a PKCS#7 (or CMS) message, -n and -k will
print a warning to stderr and dump nothing to stdout, but will otherwise
complete okay; the entire PKCS#7/CMS message will be dumped by "-s"; and "-d"
will show "0 0 2 0 0 <pkcs#7-msg-len>".
Signed-off-by: David Howells <firstname.lastname@example.org>