Document that a derivation function is used.
Document the security strength of the DRBG depending on the
compile-time configuration and how it is set up. In particular,
document how the nonce specified in SP 800-90A is set.
Mention how to link the ctr_drbg module with the entropy module.
* State explicit whether several numbers are in bits or bytes.
* Clarify whether buffer pointer parameters can be NULL.
* Explain the value of constants that are dependent on the configuration.
There is a 50% performance drop in the SCA_CM enabled encrypt and
decrypt functions. Therefore use the older version of encrypt/decypt
functions when SCA_CM is disabled.
* upstream/pr/2945:
Rename macro MBEDTLS_MAX_RAND_DELAY
Update signature of mbedtls_platform_random_delay
Replace mbedtls_platform_enforce_volatile_reads 2
Replace mbedtls_platform_enforce_volatile_reads
Add more variation to random delay countermeasure
Add random delay to enforce_volatile_reads
Update comments of mbedtls_platform_random_delay
Follow Mbed TLS coding style
Add random delay function to platform_utils
The MBEDTLS_ERR_SSL_WANT_READ and MBEDTLS_ERR_SSL_WANT_WRITE are
errors that can be ignored, so increase the hamming distance between
them and the non-ignorable errors and keep still some distance from
a success case. This mitigates an attack where single bit-flipping could
change a non-ignorable error to being an ignorable one.
- Add configuration for AES_SCA_COUNTERMEASURES to config.h. By
default the feature is disabled.
- Add AES_SCA_COUNTERMEASURES configuration check to check_config.h
- Add AES_SCA_COUNTERMEASURES test to all.sh
This commit first changes the return convention of EccPoint_mult_safer() so
that it properly reports when faults are detected. Then all functions that
call it need to be changed to (1) follow the same return convention and (2)
properly propagate UECC_FAULT_DETECTED when it occurs.
Here's the reverse call graph from EccPoint_mult_safer() to the rest of the
library (where return values are translated to the MBEDTLS_ERR_ space) and test
functions (where expected return values are asserted explicitly).
EccPoint_mult_safer()
EccPoint_compute_public_key()
uECC_compute_public_key()
pkparse.c
tests/suites/test_suite_pkparse.function
uECC_make_key_with_d()
uECC_make_key()
ssl_cli.c
ssl_srv.c
tests/suites/test_suite_pk.function
tests/suites/test_suite_tinycrypt.function
uECC_shared_secret()
ssl_tls.c
tests/suites/test_suite_tinycrypt.function
uECC_sign_with_k()
uECC_sign()
pk.c
tests/suites/test_suite_tinycrypt.function
Note: in uECC_sign_with_k() a test for uECC_vli_isZero(p) is suppressed
because it is redundant with a more thorough test (point validity) done at the
end of EccPoint_mult_safer(). This redundancy was introduced in a previous
commit but not noticed earlier.
We don't really need a secure hash for that, something like CRC32 would
probably be enough - but we have SHA-256 handy, not CRC32, so use that for the
sake of simplicity.
By semi-internal I mean functions that are only public because they're used in
more than once compilation unit in the library (for example in ecc.c and
ecc_dsa.c) but should not really be part of the public-facing API.
Same motivation as for the other parameters. This is the last one, making the
curve structure empty, so it's left with a dummy parameter for legal reasons.
-Add flow monitor, loop integrity check and variable doubling to
harden mbedtls_hmac_drbg_update_ret.
-Use longer hamming distance for nonce usage in hmac_drbg_reseed_core
-Return actual value instead of success in mbedtls_hmac_drbg_seed and
mbedtls_hmac_drbg_seed_buf
-Check illegal condition in hmac_drbg_reseed_core.
-Double buf/buf_len variables in mbedtls_hmac_drbg_random_with_add
-Add more hamming distance to MBEDTLS_HMAC_DRBG_PR_ON/OFF
This commit removes from the TinyCrypt header and source code files, the
configuration condition on MBEDTLS_USE_TINYCRYPT to include the file
contents.
This is to allow use of the library by the Factory Tool without enabling
MBEDTLS_USE_TINYCRYPT, and also removes a modification we've made to make the
code closer to the upstream TinyCrypt making it easier to maintain.
Before this commit, if a certificate only had one issue (for example, if the
"untrusted" bit was the only set in flags), an attacker that could flip this
single bit between the moment it's set and the moment flags are checked before
returning from mbedtls_x509_crt_verify() could make the entire verification
routine appear to succeed (return 0 with no bit set in flags).
Avoid that by making sure that flags always has either 0 or at least 9 bits
set during the execution of the function. However, to preserve the API, clear
the 8 extra bits before returning. This doesn't open the door to other
attacks, as fortunately the API already had redundancy: either both flags and
the return value are 0, or flags has bits set and the return value is non-zero
with at least 16 bits set (assuming 32-bit 2-complement ints).
Inspection of the generated assembly showed that before this commit, armcc 5
was optimizing away the successive reads to the volatile local variable that's
used for double-checks. Inspection also reveals that inserting a call to an
external function is enough to prevent it from doing that.
The tested versions of ARM-GCC, Clang and Armcc 6 (aka armclang) all keep the
double read, with our without a call to an external function in the middle.
The inserted function can also be changed to insert a random delay if
desired in the future, as it is appropriately places between the reads.
This can be used by Mbed TLS functions in any module to signal that a fault
attack is likely happening, so this can be appropriately handled by the
application (report, fall back to safer mode or even halt, etc.)
Previously it was returning 0 or 1, so flipping a single bit in the return
value reversed its meaning. Now it's returning the diff itself.
This is safe because in the two places it's used (signature verification and
point validation), invalid values will have a large number of bits differing
from the expected value, so diff will have a large Hamming weight.
An alternative would be to return for example -!(diff == 0), but the
comparison itself is prone to attacks (glitching the appropriate flag in the
CPU flags register, or the conditional branch if the comparison uses one). So
we'd need to protect the comparison, and it's simpler to just skip it and
return diff itself.
This is a first step in protecting against fault injection attacks: the
attacker can no longer change failure into success by flipping a single bit.
Additional steps are needed to prevent other attacks (instruction skip etc)
and will be the object of future commits.
The return value of uECC_vli_equal() should be protected as well, which will
be done in a future commit as well.
Currently functions that may return success or failure tend to do so by
returning 0 or 1. If an active physical attacker can flip a bit in memory or
registers at the right time, they may easily change a failure value into a
success value, with potentially catastrophic security consequences.
As typical attackers can only flip a few bits, an element of protection
against such attacks is to ensure a sufficient Hamming distance between
failure values and the success value. This commit introduces such values,
which will put to use in critical functions in future commits.
In addition to SUCCESS and FAILURE, a third value ATTACK_DETECTED is
introduced, which can be used later when suspicious-looking events are noticed
(static data changed when it shouldn't, double condition checking returning
inconsistent results, etc.).
Values are chosen so that Hamming distances are large, and that no value is
the complement of another, in order to avoid unwanted compiler optimisations.
Note: the error values used by Mbed TLS are already safe (assuming 32-bit
integers) as they are of the form -x with x in the range [1, 2^15) so their
Hamming distance with the success value (0) is at least 17, so it's hard for
an attacker to turn an error value into the success value (or vice-versa).
This avoids the need for each calling site to manually regularize the scalar
and randomize coordinates, which makes for simpler safe use and saves 50 bytes
of code size in the library.
-Add config option for AES encyption only to config.h. Feature is
disabled by default.
-Enable AES encrypt only feature in baremetal.h configuration
-Remove AES encypt only feature from full config
Do not reserve additionl space for mbedtls_aes_context if config
option AES_ONLY_128_BIT_KEY_LENGTH is used and PADLOCK_C is not used.
This reduces RAM usage by 96 bytes.
In baremetal configuration reserve space for 10 128-bit keys in order
to save 112 bytes of heap.
- Do not include MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH to full config
as it requires also MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
- Update check_config to check availability of flags:
MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH
MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
* mbedtls-2.16: (25 commits)
Fix compilation error
Add const to variable
Fix endianity issue when reading uint32
Increase test suite timeout
Reduce stack usage of test_suite_pkcs1_v15
Reduce stack usage of test_suite_pkcs1_v21
Reduce stack usage of test_suite_rsa
Reduce stack usage of test_suite_pk
Enable MBEDTLS_MEMORY_DEBUG in memory buffer alloc test in all.sh
Remove unnecessary memory buffer alloc and memory backtrace unsets
Disable DTLS proxy tests for MEMORY_BUFFER_ALLOC test
all.sh: restructure memory allocator tests
Add missing dependency in memory buffer alloc set in all.sh
Don't set MBEDTLS_MEMORY_DEBUG through `scripts/config.pl full`
Add cfg dep MBEDTLS_MEMORY_DEBUG->MBEDTLS_MEMORY_BUFFER_ALLOC_C
Add all.sh run with full config and ASan enabled
Add all.sh run with MBEDTLS_MEMORY_BUFFER_ALLOC_C enabled
Update documentation of exceptions for `config.pl full`
Adapt all.sh to removal of buffer allocator from full config
Disable memory buffer allocator in full config
...
Use MBEDTLS_ENTROPY_HARDWARE_ALT instead of a new global RNG
flag. When this flag is enabled, the platform provides the RNG.
When running unit tests, rnd_std_rand should be used by overriding
the mbedtls_hardware_poll.
As replacements of standard library functions, they should have the same
prototype, including return type.
While it doesn't usually matter when used directly, it does when the address
of the function is taken, as done with memset_func, used for implementing
mbedtls_platform_zeroize().
This makes a mbedtls_pk_context memory-wise equivalent to a
mbedtls_uecc_keypair and removes a dynamic allocation, making the PK layer
zero-cost in terms of memory when PK_SINGLE_TYPE is enabled.
In very reduced configurations, we don't want the overhead of maintaining a
bool just to remember if the context is valid and checking that bit at every
point of entry.
Note: so far this validity bit also served as a proxy to ensure that pk_ctx
was valid (currently this is a pointer to a dynamically-allocated buffer). In
the next series of commits, this will be changed to a statically-allocated
buffer, so there will be no question about its validity.
In the end (after this commit and the next series), a pk_context_t will be
(memory-wise) just the same as a mbedtls_uecc_keypair when SINGLE_TYPE is
enabled - meaning the PK layer will have zero memory overhead in that case.
So far, with MBEDTLS_SSL_KEEP_PEER_CERTIFICATE disabled, the SSL module relied
on a undocumented feature of the PK module: that you can distinguish between
contexts that have been setup and context that haven't. This feature is going
to go away in the case of PK_SINGLE_TYPE, as we'll soon (as in: the next
commit does that) no longer be storing the (now two-valued) pk_info member.
Note even with this change, we could still distinguish if the context has been
set up by look if pk_ctx is NULL or not, but this is also going away in the
near future (a few more commits down the road), so not a good option either.
This is the first in a series of commit aimed at removing the pk_info
structures when we're building with MBEDTLS_PK_SINGLE_TYPE enabled.
Introducing this abstraction allows us to later make it a two-valued type
(valid, invalid) instead, which is much lighter.
For optional functions, we introduce an extra macro to tell if the function is
omitted. As the C preprocessor doesn't directly support comparing strings,
testing if the _FUNC macro is defined to NULL isn't obvious. One could
probably play tricks to avoid the need for _OMIT macros, but the small amount
of (entirely local) duplication here is probably a lesser evil than extra
preprocessor complexity.
No effect for now, just declaring it here, implemented in subsequent commits.
The option requires MBEDTLS_USE_TINYCRYPT and is incompatible with
MBEDTLS_PK_RSA_ALT_SUPPORT and MBEDTLS_RSA_C.
Currently users (including the X.509 and SSL libraries) assume that if both PK
and RSA are enabled, then RSA is available through PK. If we allowed RSA to be
enabled together with PK_SINGLE_TYPE, we'd break that assumption. Going
through the code to find all place that rely on that assumption and fix them
would be cumbersome, and people who want PK_SINGLE_TYPE are unlikely to care
about RSA anyway, so let's just make them incompatible.
This is also consistent with what's done in the MD module: MD_SINGLE_HASH
requires that exactly one hash be enabled.
This achieves two related goals:
1. Those members are now only accessed via the accessor function (except in
code paths that we don't care about: those guarded by
MBEDTLS_PK_RSA_ALT_SUPPORT or MBEDTLS_ECP_RESTARTABLE)
2. When we turn on compile-time dispatch, we don't obviously don't want to
keep a runtime NULL check.
For debug this requires changing the signature or the accessor function to
return int; this is done without changing the signature of the accessed
function.
* baremetal: (78 commits)
Review corrections 6
Review corrections 5
Minor changes to tinycrypt README
Typos in the tinycrypt README
Addition of copyright statements to tinycrypt files
Add LICENSE and README for tinycrypt
Add SPDX lines to each imported TinyCrypt file
Review corrections 4
Review corrections 3
Review corrections 2
Review corrections
Update signature of BE conversion functions
Use function for 16/24/32-bit BE conversion
x509.c: Minor readability improvement
x509_crt.c: Indicate guarding condition in #else branch
X.509: Don't remove verify callback by default
Fix Doxygen warnings regarding removed verify cb+ctx parameters
ECC restart: Use optional verification mode in bad signature test
Re-implement verify chain if vrfy cbs are disabled
Add zero-cost abstraction layer for CRT verification chain
...
* mbedtls-2.16: (28 commits)
Bump version to Mbed TLS 2.16.3
Changelog entry
Check for zero length and NULL buffer pointer
ssl-opt.sh: wait for proxy to start before running the script further
Fix uninitialized variable in x509_crt
HMAC DRBG: Split entropy-gathering requests to reduce request sizes
Fix the license header of hkdf
Add a change log entry
Add a test for mlaformed ECJPAKE context
Fix handling of md failure
Add a test for signing content with a long ECDSA key
Add documentation notes about the required size of the signature buffers
Add missing MBEDTLS_ECP_C dependencies in check_config.h
Change size of preallocated buffer for pk_sign() calls
Adapt ChangeLog
Fix mpi_bigendian_to_host() on bigendian systems
Add ChangeLog entry for new function
Add ChangeLog entry
Correct deterministic ECDSA behavior
Add warning for alternative ECDSA implementations
...
- Try to follow english grammar in function documentation
- Fix too long line
- Remove additional brackets
- Follow mbedtls coding style in for-statement
-Fix MSVC compiler warnings about size_t to uint32_t conversions by
updating GET/PUT functions signature to use size_t.
-Add type casts to functions calling GET/PUT conversions
-Remove additional space after return statement
This commit re-implements the previously introduced internal
verification chain API in the case where verification callbacks
are disabled. In this situation, it is not necessary to maintain
the list of individual certificates and flags comprising the
verification chain - instead, it suffices to just keep track
of the length and the total (=merged) flags.
When verifying an X.509 certificate, the current verification logic
maintains an instance of the internal mbedtls_x509_crt_verify_chain
structure representing the state of the verification process. This
instance references the list of certificates that comprise the chain
built so far together with their verification flags. This information
must be stored during verification because it's being passed to the
verification callback at the end of verification - if the user has
specified those.
If the user hasn't specified a verification callback, it is not
necessary to maintain the list of CRTs, and it is also not necessary
to maintain verification flags for each CRT individually, as they're
merged at the end of the verification process.
To allow a readable simplification of the code in case no verification
callbacks are used, this commit introduces a zero-cost abstraction layer
for the functionality that's required from the verification chain structure:
- init/reset
- add a new CRT to the chain
- get pointer to current CRT flags
- add flags to EE certificate
- get current chain length
- trigger callbacks and get final (merged) flags
This gives flexibility for re-implementing the verification chain
structure, e.g. in the case where no verification callbacks are
provided, and there's hence no need to store CRTs and flags
individually. This will be done in a later commit.
When MBEDTLS_MD_SINGLE_HASH is set, the underlying digest's
context is embedded into mbedtls_md_context_t, which is
zeroized before the underlying digest's init() function
is called. For those digests where initialization is
zeroization, the init() call can therefore be omitted.
Similarly, when free()-ing an mbedtls_md_context_t, the
entire context is zeroized in the end, hence if the
underlying digest's free() function is zeroization,
it can be omitted.
Recall that in the default configuration, Mbed TLS provides access
digest implementations through two layers of indirection:
1) Call of MD API (e.g. mbedtls_md_update())
2) Call of function pointer from MD info structure
3) Actual digest implementation (e.g. mbedtls_sha256_update()).
Ideally, if only a single digest is enabled - say SHA-256 - then calling
mbedtls_md_update() should _directly_ jump to mbedtls_sha256_update(),
with both layers of indirection removed. So far, however, setting
MBEDTLS_MD_SINGLE_HASH will only remove the second - function pointer -
layer of indirection, while keeping the non-inlined stub implementations
of e.g. mbedtls_md_update() around.
This commit is a step towards allowing to define implementations of
the MD API as `static inline` in case we know that they are so small
that they should be defined in md.h and not in md.c.
In a nutshell, the approach is as follows: For an MD API function
mbedtls_md_xxx() that should be inlin-able, introduce its implementation
as a `static inline` wrapper `mbedtls_md_xxx_internal()` in md.h,
and then define mbedtls_md_xxx() either in md.h or in md.c, by just
calling mbedtls_md_xxx_internal().
Moving the implementations of those MD API functions that should be
inlinable to md.h requires the presence of both the MD info struct
and all specific digest wrapper functions in md.h, and this is what
this commit ensures, by moving them from md.c into a new internal
header file md_internal.h. Implementing the aforementioned wrappers for
those MD API that should be inlinable is left for subsequent commits.
This commit modifies check_config.h to check that precisely one
hash is enabled if MBEDTLS_MD_SINGLE_HASH is set.
This is not only a reasonable expectation, it is also necessary,
because test suites assume that if a digest is enabled, it is also
accessible through the MD abstraction layer.
This commit introduces the configuration option
MBEDTLS_MD_SINGLE_HASH
which can be used to hardcode support for a single digest algorithm
at compile-time, at the benefit of reduced code-size.
To use, it needs to be defined to evaluate to a macro of the form
MBEDTLS_MD_INFO_{DIGEST}, and macros MBEDTLS_MD_INFO_{DIGEST}_FIELD
must be defined, giving rise to the various aspects (name, type,
size, ...) of the chosen digest algorithm. MBEDTLS_MD_INFO_SHA256
provides an example, but other algorithms can be added if needed.
At the moment, the effect of using MBEDTLS_MD_SINGLE_HASH is that
the implementation of the MD API (e.g. mbedtls_md_update()) need no
longer to through the abstraction of the mbedtls_md_info structures
by calling their corresponding function pointers fields (akin to
virtual functions in C++), but the directly call the corresponding
core digest function (such as mbedtls_sha256_update()).
Therefore, MBEDTLS_MD_SINGLE_HASH so far removes the second layer
of indirection in the chain
User calls MD API -> MD API calls underlying digest impl'n
-> Core digest impl'n does the actual work,
but the first indirection remains, as the MD API remains untouched
and cannot yet be inlined. Studying to what extend inlining the
shortened MD API implementations would lead to further code-savings
is left for a later commit.
