trousers: Add bound check functions

Add some safe primitives for parsing RSA_KEY_PARMS, KEY_PARMS,
STORE_PUBKEY, PUBKEY, BYTE, BOOL, UINT....

https://crrev.com/c/2400950 depend on this CL.

BUG=chromium:941726
TEST=CQ

Change-Id: I69f3ca687dfbc6b3eb469cf0178461cdbe0c50fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/trousers/+/2400407
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Leo Lai <cylai@google.com>
Tested-by: joe Chou <yich@google.com>
Commit-Queue: joe Chou <yich@google.com>
2 files changed