This issue has been reported by Tuba Yavuz, Farhaan Fowze, Ken (Yihang) Bai,
Grant Hernandez, and Kevin Butler (University of Florida) and
Dave Tian (Purdue University).
In AES encrypt and decrypt some variables were left on the stack. The value
of these variables can be used to recover the last round key. To follow best
practice and to limit the impact of buffer overread vulnerabilities (like
Heartbleed) we need to zeroize them before exiting the function.
When writing a private EC key, use a constant size for the private
value, as specified in RFC 5915. Previously, the value was written
as an ASN.1 INTEGER, which caused the size of the key to leak
about 1 bit of information on average, and could cause the value to be
1 byte too large for the output buffer.
In the case of *ret we might need to preserve a 0 value throughout the
loop and therefore we need an extra condition to protect it from being
overwritten.
The value of done is always 1 after *ret has been set and does not need
to be protected from overwriting. Therefore in this case the extra
condition can be removed.
The code relied on the assumptions that CHAR_BIT is 8 and that unsigned
does not have padding bits.
In the Bignum module we already assume that the sign of an MPI is either
-1 or 1. Using this, we eliminate the above mentioned dependency.
The signature of mbedtls_mpi_cmp_mpi_ct() meant to support using it in
place of mbedtls_mpi_cmp_mpi(). This meant full comparison functionality
and a signed result.
To make the function more universal and friendly to constant time
coding, we change the result type to unsigned. Theoretically, we could
encode the comparison result in an unsigned value, but it would be less
intuitive.
Therefore we won't be able to represent the result as unsigned anymore
and the functionality will be constrained to checking if the first
operand is less than the second. This is sufficient to support the
current use case and to check any relationship between MPIs.
The only drawback is that we need to call the function twice when
checking for equality, but this can be optimised later if an when it is
needed.
Multiplication is known to have measurable timing variations based on
the operands. For example it typically is much faster if one of the
operands is zero. Remove them from constant time code.
1. variable name accoriding to the Mbed TLS coding style;
2. add a comment explaining safety of the optimization;
3. safer T2 initialization and memory zeroing on the function exit;
Record checking fails if mbedtls_ssl_check_record() is called with
external buffer. Received record sequence number is available in the
incoming record but it is not available in the ssl contexts `in_ctr`-
variable that is used when decoding the sequence number.
To fix the problem, temporarily update ssl context `in_ctr` to
point to the received record header and restore value later.
We want to explicitly disallow creating new transactions when a
transaction is already in progress. However, we were incorrectly
checking for the existence of the injected entropy file before
continuing with creating a transaction. This meant we could have a
transaction already in progress and would be able to still create a new
transaction. It also meant we couldn't start a new transaction if any
entropy had been injected. Check the transaction file instead of the
injected entropy file in order to prevent multiple concurrent
transactions.
Change the default entropy nonce length to be nonzero in some cases.
Specifically, the default nonce length is now set in such a way that
the entropy input during the initial seeding always contains enough
entropy to achieve the maximum possible security strength per
NIST SP 800-90A given the key size and entropy length.
If MBEDTLS_CTR_DRBG_ENTROPY_LEN is kept to its default value,
mbedtls_ctr_drbg_seed() now grabs extra entropy for a nonce if
MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled and either
MBEDTLS_ENTROPY_FORCE_SHA256 is enabled or MBEDTLS_SHA512_C is
disabled. If MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled, or if
the entropy module uses SHA-512, then the default value of
MBEDTLS_CTR_DRBG_ENTROPY_LEN does not require a second call to the
entropy function to achieve the maximum security strength.
This choice of default nonce size guarantees NIST compliance with the
maximum security strength while keeping backward compatibility and
performance high: in configurations that do not require grabbing more
entropy, the code will not grab more entropy than before.
Add a new function mbedtls_ctr_drbg_set_nonce_len() which configures
the DRBG instance to call f_entropy a second time during the initial
seeding to grab a nonce.
The default nonce length is 0, so there is no behavior change unless
the user calls the new function.
Add a new function mbedtls_ctr_drbg_set_nonce_len() which configures
the DRBG instance to call f_entropy a second time during the initial
seeding to grab a nonce.
The default nonce length is 0, so there is no behavior change unless
the user calls the new function.
The blinding applied to the scalar before modular inversion is
inadequate. Bignum is not constant time/constant trace, side channel
attacks can retrieve the blinded value, factor it (it is smaller than
RSA keys and not guaranteed to have only large prime factors). Then the
key can be recovered by brute force.
Reducing the blinded value makes factoring useless because the adversary
can only recover pk*t+z*N instead of pk*t.
mbedtls_ctr_drbg_seed() always set the entropy length to the default,
so a call to mbedtls_ctr_drbg_set_entropy_len() before seed() had no
effect. Change this to the more intuitive behavior that
set_entropy_len() sets the entropy length and seed() respects that and
only uses the default entropy length if there was no call to
set_entropy_len().
This removes the need for the test-only function
mbedtls_ctr_drbg_seed_entropy_len(). Just call
mbedtls_ctr_drbg_set_entropy_len() followed by
mbedtls_ctr_drbg_seed(), it works now.
Move the definitions of mbedtls_ctr_drbg_seed_entropy_len() and
mbedtls_ctr_drbg_seed() to after they are used. This makes the code
easier to read and to maintain.
mbedtls_hmac_drbg_seed() always set the entropy length to the default,
so a call to mbedtls_hmac_drbg_set_entropy_len() before seed() had no
effect. Change this to the more intuitive behavior that
set_entropy_len() sets the entropy length and seed() respects that and
only uses the default entropy length if there was no call to
set_entropy_len().
Fix a signed int overflow in mbedtls_asn1_get_int() for numbers
between INT_MAX+1 and UINT_MAX (typically 0x80000000..0xffffffff).
This was undefined behavior which in practice would typically have
resulted in an incorrect value, but which may plausibly also have
caused the postcondition (*p == initial<*p> + len) to be violated.
Credit to OSS-Fuzz.
mbedtls_entropy_func returns up to MBEDTLS_ENTROPY_BLOCK_SIZE bytes.
This is the output of a hash function and does not indicate how many
bytes of entropy went into the hash computation.
Enforce that mbedtls_entropy_func gathers a total of
MBEDTLS_ENTROPY_BLOCK_SIZE bytes or more from strong sources. Weak
sources don't count for this calculation. This is complementary to the
per-source threshold mechanism.
In particular, we define system sources with a threshold of 32. But
when using SHA-512 for the entropy accumulator,
MBEDTLS_ENTROPY_BLOCK_SIZE = 64, so users can expect 64 bytes' worth
of entropy. Before, you only got 64 bytes of entropy if there were two
sources. Now you get 64 bytes of entropy even with a single source
with a threshold of 32.
This caused problems when running multiple jobs at once, since
there was no target matching libmbedcrypto.so with the path
prefix. It only worked if it was built first, since such file was found.
Additionally, building of libmbedcrypto.so now waits for the static .a version.
Previously, recipes for both libmbedcrypto.a and libmbedcrypto.so could run
independently when running parallel jobs, which resulted in the .o files
being built twice. It could sometimes be a problem, since linking would start
when building one of the object files was still in progress (the previous one
existed). This in turn resulted in reading (and trying to link) a malformed file.
The "|" character is followed by "order-only-prerequisites", and in this case,
makes linking of the shared version of the library wait for the .a file.
Since it's guaranteed to be always built in the "all" target, it's fine to do that.
All of the .o files are only built once thanks to this change.
Add a parameter to the p_validate_slot_number method to allow the
driver to modify the persistent data.
With the current structure of the core, the persistent data is already
updated. All it took was adding a way to modify it.
When registering a key in a secure element, go through the transaction
mechanism. This makes the code simpler, at the expense of a few extra
storage operations. Given that registering a key is typically very
rare over the lifetime of a device, this is an acceptable loss.
Drivers must now have a p_validate_slot_number method, otherwise
registering a key is not possible. This reduces the risk that due to a
mistake during the integration of a device, an application might claim
a slot in a way that is not supported by the driver.
If none of the inputs to a key derivation is a
PSA_KEY_DERIVATION_INPUT_SECRET passed with
psa_key_derivation_input_key(), forbid
psa_key_derivation_output_key(). It usually doesn't make sense to
derive a key object if the secret isn't itself a proper key.
Allow a direct input as the SECRET input step in a key derivation, in
addition to allowing DERIVE keys. This makes it easier for
applications to run a key derivation where the "secret" input is
obtained from somewhere else. This makes it possible for the "secret"
input to be empty (keys cannot be empty), which some protocols do (for
example the IV derivation in EAP-TLS).
Conversely, allow a RAW_DATA key as the INFO/LABEL/SALT/SEED input to a key
derivation, in addition to allowing direct inputs. This doesn't
improve security, but removes a step when a personalization parameter
is stored in the key store, and allows this personalization parameter
to remain opaque.
Add test cases that explore step/key-type-and-keyhood combinations.
In TLS, the master secret is always a key. But EAP-TLS uses the TLS
PRF to derive an IV with an empty string for the "secret" input. The
code always stored the secret into a key slot before calling the TLS
PRF, but this doesn't work when the secret is empty, since PSA Crypto
no longer supports empty keys. Add a special case for an empty secret.
The signature must have exactly the same length as the key, it can't
be longer. Fix#258
If the signature doesn't have the correct size, that's an invalid
signature, not a problem with an output buffer size. Fix the error code.
Add test cases.
In psa_asymmetric_sign, immediately reject an empty signature buffer.
This can never be right.
Add test cases (one RSA and one ECDSA).
Change the SE HAL mock tests not to use an empty signature buffer.
Zero-length keys are rejected at creation time, so we don't need any
special handling internally.
When exporting a key, we do need to take care of the case where the
output buffer is empty, but this is easy: an empty output buffer is
never valid.
Document how mbedtls_asn1_store_named_data allocates val.p in the new
or modified entry.
Change the behavior to be more regular, always setting the new length
to val_len. This does not affect the previous documented behavior
since this aspect was not documented. This does not affect current
usage in Mbed TLS's X.509 module where calls with the same OID always
use the same size for the associated value.
At the end of `psa_hmac_setup_internal()`, the ipad is cleared.
However, the size that was given to clear was `key_len` which is larger
than the size of `ipad`.
* crypto/development: (77 commits)
all.sh: disable MEMORY_BUFFER_ALLOC in cmake asan build
Unify gcc and clang cmake flags to test with UBsan
Add an input check in psa_its_set
Remove storage errors from psa_generate_random
Update getting_started.md
Update based on Jaeden's comments.
Update getting_started.md
Fix return code warnings
Update getting_started.md
Fix warnings
Add PSA_ERROR_STORAGE_FAILURE to psa_cipher_generate_iv
Remove errorneous insert
Add STORAGE_FAILURE everywhere + add missing codes
Add storage failure to psa_mac_verify_finish
Add storage failure to psa_mac_sign_finish
Add PSA_ERROR_STORAGE_FAILURE to psa_aead_*_setup functions
Added PSA_ERROR_BAD_STATE to functions with operations
Added extra bad state case to psa_hash_setup
Add missing return codes to psa_generate_key
Add PSA_ERROR_BUFFER_TOO_SMALL to psa_mac_compute
...
We were still reusing the internal HMAC-DRBG of the deterministic ECDSA
for blinding. This meant that with cryptographically low likelyhood the
result was not the same signature as the one the deterministic ECDSA
algorithm has to produce (however it is still a valid ECDSA signature).
To correct this we seed a second HMAC-DRBG with the same seed to restore
correct behavior. We also apply a label to avoid reusing the bits of the
ephemeral key for a different purpose and reduce the chance that they
leak.
This workaround can't be implemented in the restartable case without
penalising the case where external RNG is available or completely
defeating the purpose of the restartable feature, therefore in this case
the small chance of incorrect behavior remains.
The current interface does not allow passing an RNG, which is needed for
blinding. Using the scheme's internal HMAC-DRBG results the same
blinding values for the same key and message, diminishing the
effectiveness of the countermeasure. A new function
`mbedtls_ecdsa_det_ext` is available to address this problem.
`mbedtls_ecdsa_sign_det` reuses the internal HMAC-DRBG instance to
implement blinding. The advantage of this is that the algorithm is
deterministic too, not just the resulting signature. The drawback is
that the blinding is always the same for the same key and message.
This diminishes the efficiency of blinding and leaks information about
the private key.
A function that takes external randomness fixes this weakness.
* crypto/development: (863 commits)
crypto_platform: Fix typo
des: Reduce number of self-test iterations
Fix -O0 build for Aarch64 bignum multiplication.
Make GNUC-compatible compilers use the right mbedtls_t_udbl again on Aarch64 builds.
Add optimized bignum multiplication for Aarch64.
Enable 64-bit limbs for all Aarch64 builds.
HMAC DRBG: Split entropy-gathering requests to reduce request sizes
psa: Use application key ID where necessary
psa: Adapt set_key_id() for when owner is included
psa: Add PSA_KEY_ID_INIT
psa: Don't duplicate policy initializer
crypto_extra: Use const seed for entropy injection
getting_started: Update for PSA Crypto API 1.0b3
Editorial fixes.
Cross reference 'key handles' from INVALID_HANDLE
Update documentation for psa_destroy_key
Update documentation for psa_close_key
Update psa_open_key documentation
Remove duplicated information in psa_open_key
Initialize key bits to max size + 1 in psa_import_key
...
* origin/development:
Fix uninitialized variable in x509_crt
Add a ChangeLog entry for mbedtls_net_close()
Added mbedtls_net_close and use it in ssl_fork_server to correctly disassociate the client socket from the parent process and the server socket from the child process.
Add ChangeLog entry
fix memory leak in mpi_miller_rabin()
* origin/pr/2803:
Add a ChangeLog entry for mbedtls_net_close()
Added mbedtls_net_close and use it in ssl_fork_server to correctly disassociate the client socket from the parent process and the server socket from the child process.
* origin/development: (42 commits)
Handle deleting non-existant files on Windows
Update submodule
Use 3rdparty headers from the submodule
Add Everest components to all.sh
3rdparty: Add config checks for Everest
Fix macros in benchmark.c
Update generated files
3rdparty: Fix inclusion order of CMakeLists.txt
Fix trailing whitespace
ECDH: Fix inclusion of platform.h for proper use of MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED
ECDH: Fix use of ECDH API in full handshake benchmark
ECDH: Removed unnecessary calls to mbedtls_ecp_group_load in ECDH benchmark
ECDH: Fix Everest x25519 make_public
Fix file permissions
3rdparty: Rename THIRDPARTY_OBJECTS
3rdparty: Update description of MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED
3rdparty: Fix Makefile coding conventions
ECDSA: Refactor return value checks for mbedtls_ecdsa_can_do
Add a changelog entry for Everest ECDH (X25519)
Document that curve lists can include partially-supported curves
...
Manually edit ChangeLog to ensure correct placement of ChangeLog notes.
* origin/pr/2799: (42 commits)
Handle deleting non-existant files on Windows
Update submodule
Use 3rdparty headers from the submodule
Add Everest components to all.sh
3rdparty: Add config checks for Everest
Fix macros in benchmark.c
Update generated files
3rdparty: Fix inclusion order of CMakeLists.txt
Fix trailing whitespace
ECDH: Fix inclusion of platform.h for proper use of MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED
ECDH: Fix use of ECDH API in full handshake benchmark
ECDH: Removed unnecessary calls to mbedtls_ecp_group_load in ECDH benchmark
ECDH: Fix Everest x25519 make_public
Fix file permissions
3rdparty: Rename THIRDPARTY_OBJECTS
3rdparty: Update description of MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED
3rdparty: Fix Makefile coding conventions
ECDSA: Refactor return value checks for mbedtls_ecdsa_can_do
Add a changelog entry for Everest ECDH (X25519)
Document that curve lists can include partially-supported curves
...
If we try to delete a non-existant file using del on Windows, as
can happen when running make clean, del will throw an error. Make
the Makefiles more robust by only deleting files if they exist.
This patch fixes an issue we encountered with more stringent compiler
warnings. The signature_is_good variable has a possibility of being
used uninitialized. This patch moves the use of the variable to a
place where it cannot be used while uninitialized.
Signed-off-by: Andy Gross <andy.gross@linaro.org>
The SSL context maintains a set of 'out pointers' indicating the
address at which to write the header fields of the next outgoing
record. Some of these addresses have a static offset from the
beginning of the record header, while other offsets can vary
depending on the active record encryption mechanism: For example,
if an explicit IV is in use, there's an offset between the end
of the record header and the beginning of the encrypted data to
allow the explicit IV to be placed in between; also, if the DTLS
Connection ID (CID) feature is in use, the CID is part of the
record header, shifting all subsequent information (length, IV, data)
to the back.
When setting up an SSL context, the out pointers are initialized
according to the identity transform + no CID, and it is important
to keep them up to date whenever the record encryption mechanism
changes, which is done by the helper function ssl_update_out_pointers().
During context deserialization, updating the out pointers according
to the deserialized record transform went missing, leaving the out
pointers the initial state. When attemping to encrypt a record in
this state, this lead to failure if either a CID or an explicit IV
was in use. This wasn't caught in the tests by the bad luck that
they didn't use CID, _and_ used the default ciphersuite based on
ChaChaPoly, which doesn't have an explicit IV. Changing either of
this would have made the existing tests fail.
This commit fixes the bug by adding a call to ssl_update_out_pointers()
to ssl_context_load() implementing context deserialization.
Extending test coverage is left for a separate commit.
According to SP800-90A, the DRBG seeding process should use a nonce
of length `security_strength / 2` bits as part of the DRBG seed. It
further notes that this nonce may be drawn from the same source of
entropy that is used for the first `security_strength` bits of the
DRBG seed. The present HMAC DRBG implementation does that, requesting
`security_strength * 3 / 2` bits of entropy from the configured entropy
source in total to form the initial part of the DRBG seed.
However, some entropy sources may have thresholds in terms of how much
entropy they can provide in a single call to their entropy gathering
function which may be exceeded by the present HMAC DRBG implementation
even if the threshold is not smaller than `security_strength` bits.
Specifically, this is the case for our own entropy module implementation
which only allows requesting at most 32 Bytes of entropy at a time
in configurations disabling SHA-512, and this leads to runtime failure
of HMAC DRBG when used with Mbed Crypto' own entropy callbacks in such
configurations.
This commit fixes this by splitting the seed entropy acquisition into
two calls, one requesting `security_strength` bits first, and another
one requesting `security_strength / 2` bits for the nonce.
Fixes#237.
* origin/development:
Update the crypto submodule
Use multipart PSA key derivation API
platform: Include stdarg.h where needed
Update Mbed Crypto to contain mbed-crypto#152
CMake: Add a subdirectory build regression test
README: Enable builds as a CMake subproject
ChangeLog: Enable builds as a CMake subproject
Remove use of CMAKE_SOURCE_DIR
Update library version to 2.18.0
* origin/pr/2807:
platform: Include stdarg.h where needed
Update Mbed Crypto to contain mbed-crypto#152
CMake: Add a subdirectory build regression test
README: Enable builds as a CMake subproject
ChangeLog: Enable builds as a CMake subproject
Remove use of CMAKE_SOURCE_DIR
Update library version to 2.18.0
Avoid compiler errors when MBEDTLS_PSA_CRYPTO_KEY_FILE_ID_ENCODES_OWNER
is set by using the application ID type.
[Error] psa_crypto_slot_management.c@175,9: used type 'psa_key_id_t' (aka 'psa_key_file_id_t') where arithmetic or pointer type is required
Bring Mbed TLS 2.18.0 and 2.18.1 release changes back into the
development branch. We had branched to release 2.18.0 and 2.18.1 in
order to allow those releases to go out without having to block work on
the `development` branch.
Manually resolve conflicts in the Changelog by moving all freshly addded
changes to a new, unreleased version entry.
Reject changes to include/mbedtls/platform.h made in the mbedtls-2.18
branch, as that file is now sourced from Mbed Crypto.
* mbedtls-2.18:
platform: Include stdarg.h where needed
Update Mbed Crypto to contain mbed-crypto#152
CMake: Add a subdirectory build regression test
README: Enable builds as a CMake subproject
ChangeLog: Enable builds as a CMake subproject
Remove use of CMAKE_SOURCE_DIR
Update library version to 2.18.0
* origin/development: (114 commits)
Don't redefine calloc and free
Add changelog entry to record checking
Fix compiler warning
Add debug messages
Remove duplicate entries from ChangeLog
Fix parameter name in doxygen
Add missing guards for mac usage
Improve reability and debugability of large if
Fix a typo in a comment
Fix MSVC warning
Fix compile error in reduced configurations
Avoid duplication of session format header
Implement config-checking header to context s11n
Provide serialisation API only if it's enabled
Fix compiler warning: comparing signed to unsigned
Actually reset the context on save as advertised
Re-use buffer allocated by handshake_init()
Enable serialisation tests in ssl-opt.sh
Change requirements for setting timer callback
Add setting of forced fields when deserializing
...
Breaking into a series of statements makes things easier when stepping through
the code in a debugger.
Previous comments we stating the opposite or what the code tested for (what we
want vs what we're erroring out on) which was confusing.
Also expand a bit on the reasons for these restrictions.
Modelled after the config-checking header from session s11n.
The list of relevant config flags was established by manually checking the
fields serialized in the format, and which config.h flags they depend on.
This probably deserves double-checking by reviewers.
Since the type of cid_len is unsigned but shorter than int, it gets
"promoted" to int (which is also the type of the result), unless we make the
other operand an unsigned int which then forces the expression to unsigned int
as well.
