QA:Testcase hmacalc with nss

The hmaccalc package uses NSS's digesting functions, and it isn't dealing with certificate databases, private keys, and the like, so there's very little that affects it except for being able to read its input files. Testing it amounts to using it to generate key checksums, and then checking them, verifying that it works as expected with the right key, and fails as expected with the wrong key. Interoperability with the unkeyed *sum tools is also of interest.

We test with the test vectors from the specification at build-time, but if you want to give it a workout anyway, here's the rundown for sha512hmac, with some help from sha512sum (repeating for sha1hmac/sha1sum, sha256hmac/sha256sum, and sha384hmac/sha384sum for completeness):

1. Select a group of files to checksum.

   FILESTOCHECK="$HOME/Desktop/*"

A2. Select a key to use.

   dd if=/dev/urandom bs=512 count=1 of=keyfile1

A3. Generate HMAC values over the files.

   sha512hmac -k keyfile1 $FILESTOCHECK > sums

A4. Verify the HMACs using the right key.

   sha512hmac -k keyfile1 -c sums

A5. Try to verify the HMACs using the wrong key, and see that it fails.

   dd if=/dev/urandom bs=512 count=1 of=keyfile2
   sha512hmac -k keyfile2 -c sums

B1. Generate an unkeyed digest using sha512sum.

   sha512sum -k keyfile1 $FILESTOCHECK > sums

B2. Verify the unkeyed digest using sha512hmac.

   sha512hmac -u -c sums

C1. Generate an unkeyed digest using sha512hmac.

   sha512hmac -u $FILESTOCHECK > sums

C2. Verify the unkeyed digest using sha512sum.

   sha512sum -c sums

D1. Repeat all of the tests from part A, adding "-t 260" to each

   invocation of sha512sum to instruct it to truncate its results to 80
   bits before outputting them or using them for comparison when told
   to check existing files.  (We use "260" here because it's half of
   512, plus 4.  Half of the usual output length is the lower-bound on
   values that hmaccalc will accept, and we want to try comparing using
   both shorter and longer values.  For the other tools, the value
   would have to be different -- 84 for sha1hmac, 132 for sha256hmac,
   196 for sha384hmac.)
   sha512hmac -t 260 -k keyfile1 $FILESTOCHECK > sums
   sha512hmac -t 260 -k keyfile1 -c sums

D2. Attempt to verify checksums using the same key, but with a different

   (or no) truncation size.  Each attempt should fail.
   sha512hmac -t 256 -k keyfile1 -c sums
   sha512hmac -t 264 -k keyfile1 -c sums
   sha512hmac        -k keyfile1 -c sums