fsverity-utils: introduce libfsverity

From the 'fsverity' program, split out a library 'libfsverity'.
Currently it supports computing file measurements ("digests"), and
signing those file measurements for use with the fs-verity builtin
signature verification feature.

Rewritten from patches by Jes Sorensen <jsorensen@fb.com>.
I made a lot of improvements; see patch 2 for details.

This patchset can also be found at branch "libfsverity" of
https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/...

Changes v1 => v2:
  - Fold in the Makefile fixes from Jes
  - Rename libfsverity_digest_size() and libfsverity_hash_name()
  - Improve the documentation slightly
  - If a memory allocation fails, print the allocation size
  - Use EBADMSG for invalid cert or keyfile, not EINVAL
  - Make libfsverity_find_hash_alg_by_name() handle NULL
  - Avoid introducing compiler warnings with AOSP's default cflags
  - Don't assume that BIO_new_file() sets errno
  - Other small cleanups

Eric Biggers (3):
  Split up cmd_sign.c
  Introduce libfsverity
  Add some basic test programs for libfsverity

 .gitignore                                |  10 +-
 Makefile                                  | 191 ++++++-
 cmd_sign.c                                | 633 ----------------------
 commands.h                                |  24 -
 util.h => common/common_defs.h            |  47 +-
 fsverity_uapi.h => common/fsverity_uapi.h |   0
 common/libfsverity.h                      | 132 +++++
 hash_algs.h                               |  68 ---
 lib/compute_digest.c                      | 240 ++++++++
 hash_algs.c => lib/hash_algs.c            | 129 +++--
 lib/lib_private.h                         |  83 +++
 lib/sign_digest.c                         | 399 ++++++++++++++
 lib/utils.c                               | 109 ++++
 cmd_enable.c => programs/cmd_enable.c     |  32 +-
 cmd_measure.c => programs/cmd_measure.c   |  12 +-
 programs/cmd_sign.c                       | 163 ++++++
 fsverity.c => programs/fsverity.c         |  52 +-
 programs/fsverity.h                       |  43 ++
 programs/test_compute_digest.c            |  61 +++
 programs/test_hash_algs.c                 |  38 ++
 programs/test_sign_digest.c               |  50 ++
 util.c => programs/utils.c                |   7 +-
 programs/utils.h                          |  44 ++
 testdata/cert.pem                         |  31 ++
 testdata/file.sig                         | Bin 0 -> 708 bytes
 testdata/key.pem                          |  52 ++
 26 files changed, 1770 insertions(+), 880 deletions(-)
 delete mode 100644 cmd_sign.c
 delete mode 100644 commands.h
 rename util.h => common/common_defs.h (56%)
 rename fsverity_uapi.h => common/fsverity_uapi.h (100%)
 create mode 100644 common/libfsverity.h
 delete mode 100644 hash_algs.h
 create mode 100644 lib/compute_digest.c
 rename hash_algs.c => lib/hash_algs.c (53%)
 create mode 100644 lib/lib_private.h
 create mode 100644 lib/sign_digest.c
 create mode 100644 lib/utils.c
 rename cmd_enable.c => programs/cmd_enable.c (81%)
 rename cmd_measure.c => programs/cmd_measure.c (83%)
 create mode 100644 programs/cmd_sign.c
 rename fsverity.c => programs/fsverity.c (82%)
 create mode 100644 programs/fsverity.h
 create mode 100644 programs/test_compute_digest.c
 create mode 100644 programs/test_hash_algs.c
 create mode 100644 programs/test_sign_digest.c
 rename util.c => programs/utils.c (96%)
 create mode 100644 programs/utils.h
 create mode 100644 testdata/cert.pem
 create mode 100644 testdata/file.sig
 create mode 100644 testdata/key.pem

-- 
2.26.2