TLS 1.3 record protection allows the addition of an arbitrary amount
of padding.
This commit introduces a configuration option
```
MBEDTLS_SSL_TLS13_PADDING_GRANULARITY
```
The semantics of this option is that padding is chosen in a minimal
way so that the padded plaintext has a length which is a multiple of
MBEDTLS_SSL_TLS13_PADDING_GRANULARITY.
For example, setting MBEDTLS_SSL_TLS13_PADDING_GRANULARITY to 1024
means that padded plaintexts will have length 1024, 2048, ..., while
setting it to 1 means that no padding will be used.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
The structure `mbedtls_ssl_transform` representing record protection
transformations should ideally be used through a function-based
interface only, as this will ease change of implementation as well
as the addition of new record protection routines in the future.
This commit makes a step in that direction by introducing the
helper function `ssl_transform_get_explicit_iv_len()` which
returns the size of the pre-expansion during record encryption
due to the potential addition of an explicit IV.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
This commit simplifies nonce derivation for AEAD based record protection
routines in the following way.
So far, code distinguished between the cases of GCM+CCM and ChachaPoly:
- In the case of GCM+CCM, the AEAD nonce is the concatentation
of a 4-byte Fixed IV and a dynamically chosen 8-byte IV which is prepended
to the record. In Mbed TLS, this is always chosen to be the record sequence
number, but it need not to.
- In the case of ChaChaPoly, the AEAD nonce is derived as
`( 12-byte Fixed IV ) XOR ( 0 || 8-byte dynamic IV == record seq nr )`
and the dynamically chosen IV is no longer prepended to the record.
This commit removes this distinction by always computing the record nonce
via the formula
`IV == ( Fixed IV || 0 ) XOR ( 0 || Dynamic IV )`
The ChaChaPoly case is recovered in case `Len(Fixed IV) == Len(IV)`, and
GCM+CCM is recovered when `Len(IV) == Len(Fixed IV) + Len(Dynamic IV)`.
Moreover, a getter stub `ssl_transform_aead_dynamic_iv_is_explicit()`
is introduced which infers from a transform whether the dynamically
chosen part of the IV is explicit, which in the current implementation
of `mbedtls_ssl_transform` can be derived from the helper field
`mbedtls_ssl_transform::fixed_ivlen`.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
The computation of the per-record nonce for AEAD record protection
varies with the AEAD algorithm and the TLS version in use.
This commit introduces a helper function for the nonce computation
to ease readability of the quite monolithic record encrytion routine.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
The previous record protection code added the explicit part of the
record nonce prior to encrypting the record. This temporarily leaves
the record structure in the undesireable state that the data outsie
of the interval `rec->data_offset, .., rec->data_offset + rec->data_len`
has already been written.
This commit moves the addition of the explicit IV past record encryption.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
TLS 1.3 and DTLS 1.2 + CID hide the real content type of a record
within the record's inner plaintext, while always using the same
content type for the protected record:
- TLS 1.3 always uses ApplicationData
- DTLS 1.2 + CID always uses a special CID content type.
This commit enhances the record encryption unit test to check
that the record content type is indeed correctly hidden.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
The internal functions
`ssl_cid_{build/parse}_inner_plaintext()`
implement the TLSInnerPlaintext mechanism used by DTLS 1.2 + CID
in order to allow for flexible length padding and to protect the
true content type of a record.
This feature is also present in TLS 1.3 support for which is under
development. As a preparatory step towards sharing the code between
the case of DTLS 1.2 + CID and TLS 1.3, this commit renames
`ssl_cid_{build/parse}_inner_plaintext()`
to
`ssl_{build/parse}_inner_plaintext()`.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
Add output of python3 version to output_env.sh.
Added in addition to the version of `python` as some
project's scripts try both executable names.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
Make the contributing document link to how to create a changelog rather
than just linking to the Changelog itself.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Now that lifetimes have structures and secure element drivers handle
all the lifetimes with a certain location, update driver registration
to take a location as argument rather than a lifetime.
This commit updates the tests.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Now that lifetimes have structures and secure element drivers handle
all the lifetimes with a certain location, update driver registration
to take a location as argument rather than a lifetime.
This commit updates the Mbed TLS implementation.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Now that lifetimes have structures and secure element drivers handle
all the lifetimes with a certain location, update driver registration
to take a location as argument rather than a lifetime.
This commit updates the PSA specification draft.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
