Security fixes for LoadKernel()

1) kernel_subkey is one of the input parameters; not read off disk.  KeyBlockVerify() now verifies it's not NULL unless we're only using the hash.

2) Added a check for kernel size vs. buffer size.

3) Added a check to make sure kbuf_sectors is nonzero.

BUG=chrome-os-partner:704
TEST=make && make runtests

Review URL: http://codereview.chromium.org/3186013
2 files changed