Context: There are two public key writing functions in Mbed TLS. First,
mbedtls_pk_write_pubkey(), which exports a public key in the form of a
SubjectPublicKey structure containing the raw keying material
(for example, EC point coordinates for an EC public key, without
reference to the underlying curve). Secondly, mbedtls_pk_write_pubkey_der(),
which exports a public key in the form of a SubjectPublicKeyInfo structure,
wrapping the SubjectPublicKey structure by additional information
identifying the type of public key (and for ECC, e.g., it'd also contain
the ECC group identifier). The implementation of mbedtls_pk_write_pubkey_der()
calls mbedtls_pk_write_pubkey() first and then adds the corresponding
algorithm identifier wrapper.
Both of these functions need to be provided for PSA-based opaque PK contexts,
based on PSA's public key export function.
Previously, PSA used the SubjectPublicKeyInfo structure as its export format,
so mbedtls_pk_write_pubkey_der() could be easily implemented, while
mbedtls_pk_write_pubkey() would need to trim the output of the PSA export.
The previous implementation of mbedtls_pk_write_pubkey() is not quite right
because it calls PSA export doesn't do any trimming, hence exporting the large
SubjectPublicKeyInfo structure instead of the small SubjectPublicKey.
mbedtls_pk_write_pubkey_der(), in turn, immediately returns after calling
mbedtls_pk_write_pubkey(), hence also returning the SubjectPublicKeyInfo
structure, which is correct.
By now, the PSA public key export format has changed to the smaller
SubjectPublicKey structure. This means that, now, mbedtls_pk_write_pubkey()
can be implemented by just calling the PSA export, and that
mbedtls_pk_write_pubkey_der() needs to add the algorithm information around
it, just as in the other types of PK contexts. While not correct for the
old format, the existing code for mbedtls_pk_write_pubkey() is therefore
correct for the new PSA public key format, and needs no change apart from
the missing pointer shift in the last commit.
The implementation of mbedtls_pk_write_pubkey_der() needs a special code
path for PSA-based opaque PK contexts, as the PK context only contains
the PSA key handle, and the PSA API needs to be used to extract the
underlying EC curve to be able to write the AlgorithmParameter structure
that's part of the SubjectPublicKeyInfo structure.
That's what this commit does, (hopefully) making both
mbedtls_pk_write_pubkey() and mbedtls_pk_write_pubkey_der() export
the correctly formatted public key based on the new PSA public key format.
Context: There are two public key writing functions in Mbed TLS. First,
mbedtls_pk_write_pubkey(), which exports a public key in the form of a
SubjectPublicKey structure containing the raw keying material
(for example, EC point coordinates for an EC public key, without
reference to the underlying curve). Secondly, mbedtls_pk_write_pubkey_der(),
which exports a public key in the form of a SubjectPublicKeyInfo structure,
wrapping the SubjectPublicKey structure by additional information
identifying the type of public key (and for ECC, e.g., it'd also contain
the ECC group identifier). The implementation of mbedtls_pk_write_pubkey_der()
calls mbedtls_pk_write_pubkey() first and then adds the corresponding
algorithm identifier wrapper.
Both of these functions need to be provided for PSA-based opaque PK contexts,
based on PSA's public key export function.
Previously, PSA used the SubjectPublicKeyInfo structure as its export format,
so mbedtls_pk_write_pubkey_der() could be easily implemented, while
mbedtls_pk_write_pubkey() would need to trim the output of the PSA export.
The previous implementation of mbedtls_pk_write_pubkey() is not quite right
because it calls PSA export doesn't do any trimming, hence exporting the large
SubjectPublicKeyInfo structure instead of the small SubjectPublicKey.
mbedtls_pk_write_pubkey_der(), in turn, immediately returns after calling
mbedtls_pk_write_pubkey(), hence also returning the SubjectPublicKeyInfo
structure, which is correct.
By now, the PSA public key export format has changed to the smaller
SubjectPublicKey structure. This means that, now, mbedtls_pk_write_pubkey()
can be implemented by just calling the PSA export, and that
mbedtls_pk_write_pubkey_der() needs to add the algorithm information around
it, just as in the other types of PK contexts. While not correct for the
old format, the existing code for mbedtls_pk_write_pubkey() is therefore
correct for the new PSA public key format, and needs no change apart from
the missing pointer shift in the last commit.
The implementation of mbedtls_pk_write_pubkey_der() needs a special code
path for PSA-based opaque PK contexts, as the PK context only contains
the PSA key handle, and the PSA API needs to be used to extract the
underlying EC curve to be able to write the AlgorithmParameter structure
that's part of the SubjectPublicKeyInfo structure.
That's what this commit does, (hopefully) making both
mbedtls_pk_write_pubkey() and mbedtls_pk_write_pubkey_der() export
the correctly formatted public key based on the new PSA public key format.
In mbedtls_mpi_exp_mod(), the limit check on wsize is never true when
MBEDTLS_MPI_WINDOW_SIZE is at least 6. Wrap in a preprocessor guard
to remove the dead code and resolve a Coverity finding from the
DEADCODE checker.
Change-Id: Ice7739031a9e8249283a04de11150565b613ae89
Additional changes to temporarily enable running tests:
ssl_srv.c and test_suite_ecdh use mbedtls_ecp_group_load instead of
mbedtls_ecdh_setup
test_suite_ctr_drbg uses mbedtls_ctr_drbg_update instead of
mbedtls_ctr_drbg_update_ret
Previously, PSA used SubjectPublicKeyInfo structures to serialize EC public keys.
This has recently been changed to using ECPoint structures instead, but the wrapper
making PSA ECDSA verification available through Mbed TLS' PK API hasn't yet been
adapted accordingly - which is what this commit does.
Luckily, Mbed TLS' PK API offers two functions mbedtls_pk_write_pubkey()
and mbedtls_pk_write_pubkey_der(), the latter exporting a SubjectPublicKeyInfo
structure and the former exporting an ECPoint structure in case of EC public
keys. For the adaptation of the ECDSA wrapper ecdsa_verify_wrap() it is therefore
sufficient to use mbedtls_pk_write_pubkey() instead of mbedtls_pk_write_pubkey_der().
Previously, PSA used SubjectPublicKeyInfo structures to serialize EC public keys.
This has recently been changed to using ECPoint structures instead, but the wrapper
making PSA ECDSA verification available through Mbed TLS' PK API hasn't yet been
adapted accordingly - which is what this commit does.
Luckily, Mbed TLS' PK API offers two functions mbedtls_pk_write_pubkey()
and mbedtls_pk_write_pubkey_der(), the latter exporting a SubjectPublicKeyInfo
structure and the former exporting an ECPoint structure in case of EC public
keys. For the adaptation of the ECDSA wrapper ecdsa_verify_wrap() it is therefore
sufficient to use mbedtls_pk_write_pubkey() instead of mbedtls_pk_write_pubkey_der().
The file oid.c had conditional inclusion of functions based on a config.h
define that belongs to X.509, which is backwards. For now, just include those
functions unconditionally and rely on the linker to garbage-collect them if
not used.
In the longer term X.509-specific functions are likely to be removed from
libmbedcrypto, but at this step the goal is to preserve the API (and even ABI)
of libmbedcrypto for as long as possible while separating the source trees of
Mbed Crypto and Mbed TLS.
As agreed during the workshop, temporarily move definitions to oid.h even if
they might not semantically belong here, as a short-term measure allowing to
build libmbecrypto on its own (without X.509 files present in the source tree)
but still provide all the things Mbed TLS currently expects, and more
specifically preserve the API and ABI exposed by libmbedtls.
Remove extra status handling code from psa_import_key_into_slot(). This
helps save a tiny amount of code space, but mainly serves to improve the
readability of the code.
Move pk-using code to inside psa_import_rsa_key(). This aligns the shape
of psa_import_rsa_key() to match that of psa_import_ec_private_key() and
psa_import_ec_public_key().
Remove front matter from our EC key format, to make it just the contents
of an ECPoint as defined by SEC1 section 2.3.3.
As a consequence of the simplification, remove the restriction on not
being able to use an ECDH key with ECDSA. There is no longer any OID
specified when importing a key, so we can't reject importing of an ECDH
key for the purpose of ECDSA based on the OID.
Use the PSA-native status type in psa_key_agreement_ecdh() in
preparation for us calling PSA functions (and not just Mbed TLS
functions) and still being able to return a psa_status_t (without having
to translate it to a Mbed TLS error and then back again).
Remove pkcs-1 and rsaEncryption front matter from RSA public keys. Move
code that was shared between RSA and other key types (like EC keys) to
be used only with non-RSA keys.
New function psa_copy_key().
Conflicts:
* library/psa_crypto.c: trivial conflicts due to consecutive changes.
* tests/suites/test_suite_psa_crypto.data: the same code
was added on both sides, but with a conflict resolution on one side.
* tests/suites/test_suite_psa_crypto_metadata.function: the same code
was added on both sides, but with a conflict resolution on one side.
You can use PSA_ALG_ANY_HASH to build the algorithm value for a
hash-and-sign algorithm in a policy. Then the policy allows usage with
this hash-and-sign family with any hash.
Test that PSA_ALG_ANY_HASH-based policies allow a specific hash, but
not a different hash-and-sign family. Test that PSA_ALG_ANY_HASH is
not valid for operations, only in policies.
Remove the type and bits arguments to psa_allocate_key() and
psa_create_key(). They can be useful if the implementation wants to
know exactly how much space to allocate for the slot, but many
implementations (including ours) don't care, and it's possible to work
around their lack by deferring size-dependent actions to the time when
the key material is created. They are a burden to applications and
make the API more complex, and the benefits aren't worth it.
Change the API and adapt the implementation, the units test and the
sample code accordingly.
Change the key derivation API to take inputs in multiple steps,
instead of a single one-site-fits-poorly function.
Conflicts:
* include/psa/crypto.h: merge independent changes in the documentation
of psa_key_agreement (public_key from the work on public key formats
vs general description and other parameters in the work on key derivation).
* tests/suites/test_suite_psa_crypto.data: update the key agreement
tests from the work on key derivation to the format from the work on
public key formats.
* tests/suites/test_suite_psa_crypto_metadata.function: reconcile the
addition of unrelated ALG_IS_xxx macros
Get rid of "key selection" algorithms (of which there was only one:
raw key selection).
Encode key agreement by combining a raw key agreement with a KDF,
rather than passing the KDF as an argument of a key agreement macro.
Use separate step types for a KDF secret and for the private key in a
key agreement.
Determine which key type is allowed from the step type, independently
of the KDF.
Forbid raw inputs for certain steps. They definitely should be
forbidden for asymmetric keys, which are structured. Also forbid them
for KDF secrets: the secrets are supposed to be keys, even if they're
unstructured.
Change the import/export format of DSA and DH public keys to use just
the key data, without a SubjectPublicKeyInfo wrapping.
Add an API to set and query domain parameters for DSA and DH keys.
DSA and static DH need extra domain parameters. Instead of passing these
in with the keys themselves, add get and set functions to set and
retrieve this information about keys.
Add a new function mbedtls_asn1_write_named_bitstring() that removes
trailing 0s at the end of DER encoded bitstrings. The function is
implemented according to Hanno Becker's suggestions.
This commit also changes the functions x509write_crt_set_ns_cert_type
and crt_set_key_usage to call the new function as the use named
bitstrings instead of the regular bitstrings.
When MBEDTLS_PSA_CRYPTO_SPM is defined, the code is being built for SPM (Secure Partition Manager)
integration which separates the code into two parts: NSPE (Non-Secure Processing Environment) and SPE
(Secure Processing Environment). When building for the SPE, an additional header file should be included.
Remove extra status handling code from psa_import_key_into_slot(). This
helps save a tiny amount of code space, but mainly serves to improve the
readability of the code.
Move pk-using code to inside psa_import_rsa_key(). This aligns the shape
of psa_import_rsa_key() to match that of psa_import_ec_private_key() and
psa_import_ec_public_key().
Remove front matter from our EC key format, to make it just the contents
of an ECPoint as defined by SEC1 section 2.3.3.
As a consequence of the simplification, remove the restriction on not
being able to use an ECDH key with ECDSA. There is no longer any OID
specified when importing a key, so we can't reject importing of an ECDH
key for the purpose of ECDSA based on the OID.
Use the PSA-native status type in psa_key_agreement_ecdh() in
preparation for us calling PSA functions (and not just Mbed TLS
functions) and still being able to return a psa_status_t (without having
to translate it to a Mbed TLS error and then back again).
You can use PSA_ALG_ANY_HASH to build the algorithm value for a
hash-and-sign algorithm in a policy. Then the policy allows usage with
this hash-and-sign family with any hash.
Test that PSA_ALG_ANY_HASH-based policies allow a specific hash, but
not a different hash-and-sign family. Test that PSA_ALG_ANY_HASH is
not valid for operations, only in policies.
Remove pkcs-1 and rsaEncryption front matter from RSA public keys. Move
code that was shared between RSA and other key types (like EC keys) to
be used only with non-RSA keys.
Previously we weren't initializing the freshly allocated ECP keypair
when importing private EC keys. This didn't seem to cause problems, at
least according to our current test coverage, but it's better to ensure
we don't have a partially initialized object by explicitly initializing
the keypair.
Return the error code if failed, instead of returning value `1`.
If not failed, return the call of the underlying function,
in `mbedtls_ecdsa_genkey()`.
Use `cmake -D CMAKE_BUILD_TYPE=Asan` rather than manually setting
`-fsanitize=address`. This lets cmake determine the necessary compiler
and linker flags.
With UNSAFE_BUILD on, force -Wno-error. This is necessary to build
with MBEDTLS_TEST_NULL_ENTROPY.
Use `cmake -D CMAKE_BUILD_TYPE=Asan` rather than manually setting
`-fsanitize=address`. This lets cmake determine the necessary compiler
and linker flags.
With UNSAFE_BUILD on, force -Wno-error. This is necessary to build
with MBEDTLS_TEST_NULL_ENTROPY.
Add new initializers for key policies and use them in our docs, example
programs, tests, and library code. Prefer using the macro initializers
due to their straightforwardness.
mbedtls_mpi_read_binary() calls memcpy() with the source pointer being
the source pointer passed to mbedtls_mpi_read_binary(), the latter may
be NULL if the buffer length is 0 (and this happens e.g. in the ECJPAKE
test suite). The behavior of memcpy(), in contrast, is undefined when
called with NULL source buffer, even if the length of the copy operation
is 0.
This commit fixes this by explicitly checking that the source pointer is
not NULL before calling memcpy(), and skipping the call otherwise.
Context: The function `mbedtls_mpi_fill_random()` uses a temporary stack
buffer to hold the random data before reading it into the target MPI.
Problem: This is inefficient both computationally and memory-wise.
Memory-wise, it may lead to a stack overflow on constrained devices with
limited stack.
Fix: This commit introduces the following changes to get rid of the
temporary stack buffer entirely:
1. It modifies the call to the PRNG to output the random data directly
into the target MPI's data buffer.
This alone, however, constitutes a change of observable behaviour:
The previous implementation guaranteed to interpret the bytes emitted by
the PRNG in a big-endian fashion, while rerouting the PRNG output into the
target MPI's limb array leads to an interpretation that depends on the
endianness of the host machine.
As a remedy, the following change is applied, too:
2. Reorder the bytes emitted from the PRNG within the target MPI's
data buffer to ensure big-endian semantics.
Luckily, the byte reordering was already implemented as part of
`mbedtls_mpi_read_binary()`, so:
3. Extract bigendian-to-host byte reordering from
`mbedtls_mpi_read_binary()` to a separate internal function
`mpi_bigendian_to_host()` to be used by `mbedtls_mpi_read_binary()`
and `mbedtls_mpi_fill_random()`.
The calls to cipher_finish didn't actually do anything:
- the cipher mode is always ECB
- in that case cipher_finish() only sets *olen to zero, and returns either 0
or an error depending on whether there was pending data
- olen is a local variable in the caller, so setting it to zero right before
returning is not essential
- the return value of cipher_finis() was not checked by the caller so that's
not useful either
- the cipher layer does not have ALT implementations so the behaviour
described above is unconditional on ALT implementations (in particular,
cipher_finish() can't be useful to hardware as (with ECB) it doesn't call any
functions from lower-level modules that could release resources for example)
Since the calls are causing issues with parameter validation, and were no
serving any functional purpose, it's simpler to just remove them.
Somehow, mbedtls_sha256_ret() is defined even if MBEDTLS_SHA256_ALT
is set, and it is using SHA256_VALIDATE_RET. The documentation should
be enhanced to indicate that MBEDTLS_SHA256_ALT does _not_ replace
the entire module, but only the core SHA-256 functions.
Somehow, mbedtls_sha512_ret() is defined even if MBEDTLS_SHA512_ALT
is set, and it is using SHA512_VALIDATE_RET. The documentation should
be enhanced to indicate that MBEDTLS_SHA512_ALT does _not_ replace
the entire module, but only the core SHA-512 functions.
Somehow, mbedtls_sha1_ret() is defined even if MBEDTLS_SHA1_ALT
is set, and it is using SHA1_VALIDATE_RET. The documentation should
be enhanced to indicate that MBEDTLS_SHA1_ALT does _not_ replace
the entire module, but only the core SHA-1 functions.
Document when a context must be initialized or not, when it must be
set up or not, and whether it needs a private key or a public key will
do.
The implementation is sometimes more liberal than the documentation,
accepting a non-set-up context as a context that can't perform the
requested information. This preserves backward compatibility.
The MPI_VALIDATE_RET() macro cannot be used for parameter
validation of mbedtls_mpi_lsb() because this function returns
a size_t.
Use the underlying MBEDTLS_INTERNAL_VALIDATE_RET() insteaed,
returning 0 on failure.
Also, add a test for this behaviour.
A 0-length buffer for the key is a legitimate edge case. Ensure that
it works, even with buf=NULL. Document the key and keylen parameters.
There are already test cases for parsing an empty buffer. A subsequent
commit will add tests for writing to an empty buffer.
Add checks for null pointers under MBEDTLS_CHECK_PARAMS.
In functions that perform operations with a context, only check if the
context pointer is non-null under MBEDTLS_CHECK_PARAMS. In the default
configuration, unconditionally dereference the context pointer.
In functions that query a context, support NULL as a
pointer-to-context argument, and return the same value as for a
context which has been initialized but not set up.
- The validity of the input and output parameters is checked by
parameter validation.
- A PRNG is required in public mode only (even though it's also
recommended in private mode), so move the check to the
corresponding branch.
The check was already done later when calling ECB, (as evidenced by the tests
passing, which have a call with data_unit set to NULL), but it's more readable
to have it here too, and more helpful when debugging.
Some of the documentation is obsolete in its reference to key slots
when it should discuss key handles. This may require a further pass,
possibly with some reorganization of error codes.
Update the documentation of functions that modify key slots (key
material creation and psa_set_key_policy()) to discuss how they affect
storage.
Move psa_load_persistent_key_into_slot,
psa_internal_make_key_persistent and psa_internal_release_key_slot to
the slot management module.
Expose psa_import_key_into_slot from the core.
After this commit, there are no longer any functions declared in
psa_crypto_slot_management.h and defined in psa_crypto.c. There are
still function calls in both directions between psa_crypto.c and
psa_crypto_slot_management.c.
Move the key slot array and its initialization and wiping to the slot
management module.
Also move the lowest-level key slot access function psa_get_key_slot
and the auxiliary function for slot allocation
psa_internal_allocate_key_slot to the slot management module.
Since Mbed TLS 2.10, there is a single copy of
mbedtls_platform_zeroize for the whole library instead of one per
module. Update the PSA crypto module accordingly.
This commit finishes the removal of support for direct access to key
slots in psa_crypto.c.
This marks the end of the necessary phase of the transition to key
handles. The code should subsequently be refactored to move key slot
management from psa_crypto.c to psa_crypto_slot_management.c.
This commit marks the beginning of the removal of support for direct
access to key slots. From this commit on, programs that use
psa_key_slot_t will no longer compile.
Subsequent commits will remove the now-unused legacy support in
psa_crypto.c.
The code only worked if psa_key_id_t (formerly psa_key_slot_t)
promoted to int and every value fit in int. Now the code only assumes
that psa_key_id_t is less wide than unsigned long, which is the case
since psa_key_id_t is a 32-bit type in our implementation.
