In the previous bounds check `(*p) > end - len`, the computation
of `end - len` might underflow if `end` is within the first 64KB
of the address space (note that the length `len` is controlled by
the peer). In this case, the bounds check will be bypassed, leading
to `*p` exceed the message bounds by up to 64KB when leaving
`ssl_parse_server_psk_hint()`. In a pure PSK-based handshake,
this doesn't seem to have any consequences, as `*p*` is not accessed
afterwards. In a PSK-(EC)DHE handshake, however, `*p` is read from
in `ssl_parse_server_ecdh_params()` and `ssl_parse_server_dh_params()`
which might lead to an application crash of information leakage.
Functional tests for various payload sizes and output buffer sizes.
When the padding is bad or the plaintext is too large for the output
buffer, verify that function writes some outputs. This doesn't
validate that the implementation is time-constant, but it at least
validates that it doesn't just return early without outputting anything.
Get rid of the variable p. This makes it more apparent where the code
accesses the buffer at an offset whose value is sensitive.
No intended behavior change in this commit.
Rather than doing the quadratic-time constant-memory-trace on the
whole working buffer, do it on the section of the buffer where the
data to copy has to lie, which can be significantly smaller if the
output buffer is significantly smaller than the working buffer, e.g.
for TLS RSA ciphersuites (48 bytes vs MBEDTLS_MPI_MAX_SIZE).
In mbedtls_rsa_rsaes_pkcs1_v15_decrypt, use size_greater_than (which
is based on bitwise operations) instead of the < operator to compare
sizes when the values being compared must not leak. Some compilers
compile < to a branch at least under some circumstances (observed with
gcc 5.4 for arm-gnueabi -O9 on a toy program).
Replace memmove(to, to + offset, length) by a functionally equivalent
function that strives to make the same memory access patterns
regardless of the value of length. This fixes an information leak
through timing (especially timing of memory accesses via cache probes)
that leads to a Bleichenbacher-style attack on PKCS#1 v1.5 decryption
using the plaintext length as the observable.
mbedtls_rsa_rsaes_pkcs1_v15_decrypt takes care not to reveal whether
the padding is valid or not, even through timing or memory access
patterns. This is a defense against an attack published by
Bleichenbacher. The attacker can also obtain the same information by
observing the length of the plaintext. The current implementation
leaks the length of the plaintext through timing and memory access
patterns.
This commit is a first step towards fixing this leak. It reduces the
leak to a single memmove call inside the working buffer.
Make the function more robust by taking an arbitrary zero/nonzero
argument instead of insisting on zero/all-bits-one. Update and fix its
documentation.
mbedtls_rsa_rsaes_pkcs1_v15_decrypt took care of calculating the
padding length without leaking the amount of padding or the validity
of the padding. However it then skipped the copying of the data if the
padding was invalid, which could allow an adversary to find out
whether the padding was valid through precise timing measurements,
especially if for a local attacker who could observe memory access via
cache timings.
Avoid this leak by always copying from the decryption buffer to the
output buffer, even when the padding is invalid. With invalid padding,
copy the same amount of data as what is expected on valid padding: the
minimum valid padding size if this fits in the output buffer,
otherwise the output buffer size. To avoid leaking payload data from
an unsuccessful decryption, zero the decryption buffer before copying
if the padding was invalid.
Remove the trailing whitespace from the inline assembly for AMD64 target, to
overcome a warning in Clang, which was objecting to the string literal
generated by the inline assembly being greater than 4096 characters specified
by the ISO C99 standard. (-Woverlength-strings)
This is a cosmetic change and doesn't change the logic of the code in any way.
This change only fixes the problem for AMD64 target, and leaves other targets as
they are.
Fixes#482.
* The variables `csr` and `issuer_crt` are initialized but not freed.
* The variable `entropy` is unconditionally freed in the cleanup section
but there's a conditional jump to that section before its initialization.
This cmmot Moves it to the other initializations happening before the
first conditional jump to the cleanup section.
Fixes#1422.
Exclude ".git" directories anywhere. This avoids spurious errors in git
checkouts that contain branch names that look like a file
check-files.py would check. Fix#1713
Exclude "mbed-os" anywhere and "examples" from the root. Switch to the
new mechanism to exclude "yotta/module". These are directories where
we store third-party files that do not need to match our preferences.
Exclude "cov-int" from the root. Fix#1691
Changes run-test-suites.pl to filter out directories, and select only files
as on OSX, test coverage tests create .dSYM directories which were being
accidentally selected to execute.
Changes the IP address to bind to for dtls_server.c to be "::" or optionally
"0.0.0.0" if the preprocessor symbol FORCE_IPV4 is defined.
Also changes the destinaton IP address for dtls_client.c to be "::1" or if
FORCE_IPV4 symbol is defined "127.0.0.1".
This change allows on compilation dtls_server.c and dtls_client.c to both be
compiled to use either IPv4 or IPv6 so out of the box they will work together
without problem, and to avoid dtls_server.c binding to IPv6 and dtls_client.c
binding to IPv4.
Generate the documentation from include and doxygen/input only. Don't
get snared by files containing Doxygen comments that lie in other
directories such as tests, yotta, crypto/include, ...
The only difference this makes in a fresh checkout is that the
documentation no longer lists target_config.h. This file is from
yotta, does not contain any Doxygen comment, and its inclusion in the
rendered documentation was clearly an oversight.
The run-test-suites.pl script was executing all files of the form 'test_suite*'
which were either executable or ended with a .exe extension.
On some filesystems, such as through network shares or VMs, which are
abstracting one set of file permissions to Unix permissions, may set the
executable permissions on all files, whether they're executable or not.
That was leading to the run-test-suites.pl script to attempt to execute the .c
intermediate files because they followed the form 'test_suite_*.c'. This change
now excludes them, just in case they accidentally have execute permissions.
Deprecate mbedtls_hmac_drbg_update (which returns void) in favor of a
new function mbedtls_hmac_drbg_update_ret which reports error. The old
function is not officially marked as deprecated in this branch because
this is a stable maintenance branch.
Deprecate mbedtls_ctr_drbg_update (which returns void) in favor of a
new function mbedtls_ctr_drbg_update_ret which reports error. The old
function is not officially marked as deprecated in this branch because
this is a stable maintenance branch.
