This commit adds some explicit downcasts from `size_t` to `uint8_t` in
the RSASSA signature encoding function `rsa_rsassa_pkcs1_v15_encode`.
The truncation is safe as it has been checked beforehand that the
respective values are in the range of a `uint8_t`.
1) `mbedtls_rsa_import_raw` used an uninitialized return
value when it was called without any input parameters.
While not sensible, this is allowed and should be a
succeeding no-op.
2) The MPI test for prime generation missed a return value
check for a call to `mbedtls_mpi_shift_r`. This is neither
critical nor new but should be fixed.
3) Both the RSA keygeneration example program and the
RSA test suites contained code initializing an RSA context
after a potentially failing call to CTR DRBG initialization,
leaving the corresponding RSA context free call in the
cleanup section of the respective function orphaned.
While this defect existed before, Coverity picked up on
it again because of newly introduced MPI's that were
also wrongly initialized only after the call to CTR DRBG
init. The commit fixes both the old and the new issue
by moving the initializtion of both the RSA context and
all MPI's prior to the first potentially failing call.
The function `mbedtls_rsa_complete` is supposed to guarantee that
RSA operations will complete without failure. In contrast, it does
not ensure consistency of parameters, which is the task of the
checking functions `rsa_check_pubkey` and `rsa_check_privkey`.
Previously, the maximum allowed size of the RSA modulus was checked
in `mbedtls_rsa_check_pubkey`. However, exceeding this size would lead
to failure of some RSA operations, hence this check belongs to
`mbedtls_rsa_complete` rather than `mbedtls_rsa_check_pubkey`.
This commit moves it accordingly.
Remove a check introduced in the previous buffer overflow fix with keys of
size 8N+1 which the subsequent fix for buffer start calculations made
redundant.
Added a changelog entry for the buffer start calculation fix.
For a key of size 8N+1, check that the first byte after applying the
public key operation is 0 (it could have been 1 instead). The code was
incorrectly doing a no-op check instead, which led to invalid
signatures being accepted. Not a security flaw, since you would need the
private key to craft such an invalid signature, but a bug nonetheless.
The check introduced by the previous security fix was off by one. It
fixed the buffer overflow but was not compliant with the definition of
PSS which technically led to accepting some invalid signatures (but
not signatures made without the private key).
Fix buffer overflow in RSA-PSS signature verification when the hash is
too large for the key size. Found by Seth Terashima, Qualcomm.
Added a non-regression test and a positive test with the smallest
permitted key size for a SHA-512 hash.
This commit splits off the RSA helper functions into separate headers and
compilation units to have a clearer separation of the public RSA interface,
intended to be used by end-users, and the helper functions which are publicly
provided only for the benefit of designers of alternative RSA implementations.
It is not necessary to pass a CSPRNG to `mbedtls_rsa_deduce_moduli`, as there
exist well-working static strategies, and even if a PRNG is preferred, a
non-secure one would be sufficient.
Further, the implementation is changed to use a static strategy for the choice
of candidates which according to some benchmarks even performs better than the
previous one using random candidate choices.
This commit modifies the PKCS1 v1.5 signature verification function `mbedtls_rsa_rsassa_pkcs1_v15_verify` to prepare the
expected PKCS1-v1.5-encoded hash using the function also used by the signing routine `mbedtls_rsa_rsassa_pkcs1_v15_sign`
and comparing it to the provided byte-string afterwards. This comes at the benefits of (1) avoiding any error-prone
parsing, (2) removing the dependency of the RSA module on the ASN.1 parsing module, and (3) reducing code size.
This commit moves the code preparing PKCS1 v1.5 encoded hashes from `mbedtls_rsa_rsassa_pkcs1_v15_sign` to a separate
non-public function `rsa_rsassa_pkcs1_v15_encode`. This code-path will then be re-used by the signature verification function
`mbetls_rsa_rsassa_pkcs1_v15_verify` in a later commit.
Original intention was to be allowed to perform in-place operations like changing the byte-order before importing
parameters into an HSM. Now a copy is needed in this case, but there's no more danger of a user expecting the arguments
to be left untouched.
This commit changes the implementation of `mbedtls_rsa_get_len` to return
`ctx->len` instead of always re-computing the modulus' byte-size via
`mbedtls_mpi_size`.
If CRT is not used, the helper fields CRT are not assumed to be present in the
RSA context structure, so do the verification directly in this case. If CRT is
used, verification could be done using CRT, but we're sticking to ordinary
verification for uniformity.
This commit adds the function mbedtls_rsa_validate_crt for validating a set of CRT parameters. The function
mbedtls_rsa_check_crt is simplified accordingly.
Primality testing is guarded by the configuration flag MBEDTLS_GENPRIME and used in the new RSA helper functions. This
commit adds a corresponding preprocessor directive.
Alternative RSA implementations can be provided by defining MBEDTLS_RSA_ALT in
config.h, defining an mbedtls_rsa_context struct in a new file rsa_alt.h and
re-implementing the RSA interface specified in rsa.h.
Through the previous reworkings, the adherence to the interface is the only
implementation obligation - in particular, implementors are free to use a
different layout for the RSA context structure.
The RSA private key functions rsa_rsaes_pkcs1_v15_decrypt and
rsa_rsaes_oaep_decrypt put sensitive data (decryption results) on the
stack. Wipe it before returning.
Thanks to Laurent Simon for reporting this issue.
The sliding window exponentiation algorithm is vulnerable to
side-channel attacks. As a countermeasure we add exponent blinding in
order to prevent combining the results of different measurements.
This commit handles the case when the Chinese Remainder Theorem is used
to accelerate the computation.
The sliding window exponentiation algorithm is vulnerable to
side-channel attacks. As a countermeasure we add exponent blinding in
order to prevent combining the results of fifferent measurements.
This commits handles the case when the Chinese Remainder Theorem is NOT
used to accelerate computations.
The test case was generated by modifying our signature code so that it
produces a 7-byte long padding (which also means garbage at the end, so it is
essential in to check that the error that is detected first is indeed the
padding rather than the final length check).
The PKCS#1 standard says nothing about the relation between P and Q
but many libraries guarantee P>Q and mbed TLS did so too in earlier
versions.
This commit restores this behaviour.
Once the mutex is acquired, we must goto cleanup rather that return.
Since cleanup adjusts the return value, adjust that in test cases.
Also, at cleanup we don't want to overwrite 'ret', or we'll loose track of
errors.
see #257
* commit 'ce60fbe':
Fix potential timing difference with RSA PMS
Update Changelog for recent merge
Added more constant-time code and removed biases in the prime number generation routines.
Conflicts:
library/bignum.c
library/ssl_srv.c
* mbedtls-1.3:
Add missing depends in x509 programs
Simplify ifdef checks in programs/x509
Fix thread safety issue in RSA operations
Add test certificate for bitstring in DN
Add support for X.520 uniqueIdentifier
Accept bitstrings in X.509 names
The race was due to mpi_exp_mod storing a Montgomery coefficient in the
context (RM, RP, RQ).
The fix was verified with -fsanitize-thread using ssl_pthread_server and two
concurrent clients.
A more fine-grained fix should be possible, locking just enough time to check
if those values are OK and set them if not, rather than locking for the whole
mpi_exp_mod() operation, but it will be for later.
Note from future self: actually md_init_ctx will be re-introduced with the
same signature later, and a new function with the additional argument will be
added.
- more freedom for us to change it in the future
- enforces hygiene
- performance impact of making accessors no longer inline should really be
negligible
A new OID module has been created that contains the main OID searching
functionality based on type-dependent arrays. A base type is used to
contain the basic values (oid_descriptor_t) and that type is extended to
contain type specific information (like a pk_alg_t).
As a result the rsa sign and verify function prototypes have changed. They
now expect a md_type_t identifier instead of the removed RSA_SIG_XXX
defines.
All OID definitions have been moved to oid.h
All OID matching code is in the OID module.
The RSA PKCS#1 functions cleaned up as a result and adapted to use the
MD layer.
The SSL layer cleanup up as a result and adapted to use the MD layer.
The X509 parser cleaned up and matches OIDs in certificates with new
module and adapted to use the MD layer.
The X509 writer cleaned up and adapted to use the MD layer.
Apps and tests modified accordingly
Split rsa_pkcs1_encrypt() into rsa_rsaes_oaep_encrypt() and
rsa_rsaes_pkcs1_v15_encrypt()
Split rsa_pkcs1_decrypt() into rsa_rsaes_oaep_decrypt() and
rsa_rsaes_pkcs1_v15_decrypt()
Split rsa_pkcs1_sign() into rsa_rsassa_pss_sign() and
rsa_rsassa_pkcs1_v15_sign()
Split rsa_pkcs1_verify() into rsa_rsassa_pss_verify() and
rsa_rsassa_pkcs1_v15_verify()
The original functions exist as generic wrappers to these functions.
