also: do a small optimisation in borg check:
if the type of the repo object is not ROBJ_ARCHIVE_META, we
can skip the object, it can not contain valid archive meta data.
if the type is correct, this is already a sufficient check, so
we can be quite sure that there will be valid archive metadata
in the object.
writing: put type into repoobj metadata
reading: check wanted type against type we got
repoobj metadata is encrypted and authenticated.
repoobj data is encrypted and authenticated, also (separately).
encryption and decryption of both metadata and data get the
same "chunk ID" as AAD, so both are "bound" to that (same) ID.
a repo-side attacker can neither see cleartext metadata/data,
nor successfully tamper with it (AEAD decryption would fail).
also, a repo-side attacker could not replace a repoobj A with a
differently typed repoobj B without borg noticing:
- the metadata/data is cryptographically bound to its ID.
authentication/decryption would fail on mismatch.
- the type check would fail.
thus, the problem (see CVEs in changelog) solved in borg 1 by the
manifest and archive TAMs is now already solved by the type check.
For many use cases, the repo-wide "rcompress" is more efficient.
Also, recreate --recompress calls add_chunk with overwrite=True,
which is unsupported with the AdHocCache.
twine is only needed at release time, no need
for all developers or all test runs to install
this.
also, some requirement of twine needs a rust
compiler, so if there is no rust compiler,
automated runs will abort due to that.
remove a lot of complexity from the code that was just there to
support legacy borg versions < 1.0.9 which did not TAM authenticate
the manifest.
since then, borg writes TAM authentication to the manifest,
even if the repo is unencrypted.
if the repo is unencrypted, it did not check the somehow pointless
authentication that was generated without any secret, but
if we add that fake TAM, we can also verify the fake TAM.
if somebody explicitly switches off all crypto, they can not
expect authentication.
for everybody else, borg now always generates the TAM and also
verifies it.
