This is the beginning of a series of commits refactoring the chain
building/verification functions in order to:
- make it simpler to understand and work with
- prepare integration of restartable ECC
md() already checks for md_info == NULL. Also, in the future it might also
return other errors (eg hardware errors if acceleration is used), so it make
more sense to check its return value than to check for NULL ourselves and then
assume no other error can occur.
Also, currently, md_info == NULL can never happen except if the MD and OID modules
get out of sync, or if the user messes with members of the x509_crt structure
directly.
This commit does not change the current behaviour, which is to treat MD errors
the same way as a bad signature or no trusted root.
Currently only SHA1 is supported as PRF algorithm for PBKDF2
(PKCS#5 v2.0).
This means that keys encrypted and authenticated using
another algorithm of the SHA family cannot be decrypted.
This deficiency has become particularly incumbent now that
PKIs created with OpenSSL1.1 are encrypting keys using
hmacSHA256 by default (OpenSSL1.0 used PKCS#5 v1.0 by default
and even if v2 was forced, it would still use hmacSHA1).
Enable support for all the digest algorithms of the SHA
family for PKCS#5 v2.0.
Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
On x32 systems, pointers are 4-bytes wide and are therefore stored in %e?x
registers (instead of %r?x registers). These registers must be accessed using
"addl" instead of "addq", however the GNU assembler will acccept the generic
"add" instruction and determine the correct opcode based on the registers
passed to it.
A new test for mbedtls_timing_alarm(0) was introduced in PR 1136, which also
fixed it on Unix. Apparently test results on MinGW were not checked at that
point, so we missed that this new test was also failing on this platform.
The corner cases fixed include:
* Allocating a buffer of size 0. With this change, the allocator now
returns a NULL pointer in this case. Note that changes in pem.c and
x509_crl.c were required to fix tests that did not work under this
assumption.
* Initialising the allocator with less memory than required for headers.
* Fix header chain checks for uninitialised allocator.
Fix compilation error on Mingw32 when `_TRUNCATE` is defined. Use
`_TRUNCATE` only if `__MINGW32__` not defined. Fix suggested by
Thomas Glanzmann and Nick Wilson on issue #355
The SHA-256 / SHA-512 context used for entropy mixing in entropy.c
was previously reset by zeroization. The commit replaces this by
a pair of calls to `mbedtls_shaxxx_init` and `mbedtls_shaxxx_free`
which is safe also for alternative implementations of SHA-256 or
SHA-512 for which zeroization might not be a proper reset.
The entropy context contains a SHA-256 or SHA-512 context for entropy
mixing, but doesn't initialize / free this context properly in the
initialization and freeing functions `mbedtls_entropy_init` and
`mbedtls_entropy_free` through a call to `mbedtls_sha{256/512}_init`
resp. `mbedtls_sha{256/512}_free`. Instead, only a zeroization of the
entire entropy structure is performed. This doesn't lead to problems
for the current software implementations of SHA-256 and SHA-512 because
zeroization is proper initialization for them, but it may (and does)
cause problems for alternative implementations of SHA-256 and SHA-512
that use context structures that cannot be properly initialized through
zeroization. This commit fixes this. Found and fix suggested by ccli8.
* mbedtls-2.1:
selftest: fix build error in some configurations
Timing self test: shorten redundant tests
Timing self test: increased duration
Timing self test: increased tolerance
selftest: allow excluding a subset of the tests
selftest: allow running a subset of the tests
selftest: fixed an erroneous return code
selftest: refactor to separate the list of tests from the logic
Timing self test: print some diagnosis information
mbedtls_timing_get_timer: don't use uninitialized memory
timing interface documentation: minor clarifications
Timing: fix mbedtls_set_alarm(0) on Unix/POSIX
Increase the duration of the self test, otherwise it tends to fail on
a busy machine even with the recently upped tolerance. But run the
loop only once, it's enough for a simple smoke test.
mbedtls_timing_self_test fails annoyingly often when running on a busy
machine such as can be expected of a continous integration system.
Increase the tolerances in the delay test, to reduce the chance of
failures that are only due to missing a deadline on a busy machine.
Print some not-very-nice-looking but helpful diagnosis information if
the timing selftest fails. Since the failures tend to be due to heavy
system load that's hard to reproduce, this information is necessary to
understand what's going on.
mbedtls_timing_get_timer with reset=1 is called both to initialize a
timer object and to reset an already-initialized object. In an
initial call, the content of the data structure is indeterminate, so
the code should not read from it. This could crash if signed overflows
trap, for example.
As a consequence, on reset, we can't return the previously elapsed
time as was previously done on Windows. Return 0 as was done on Unix.
The POSIX/Unix implementation of mbedtls_set_alarm did not set the
mbedtls_timing_alarmed flag when called with 0, which was inconsistent
with what the documentation implied and with the Windows behavior.
* restricted/pr/412:
Correct record header size in case of TLS
Don't allocate space for DTLS header if DTLS is disabled
Improve debugging output
Adapt ChangeLog
Add run-time check for handshake message size in ssl_write_record
Add run-time check for record content size in ssl_encrypt_buf
Add compile-time checks for size of record content and payload
In a previous PR (Fix heap corruption in implementation of truncated HMAC
extension #425) the place where MAC is computed was changed from the end of
the SSL I/O buffer to a local buffer (then (part of) the content of the local
buffer is either copied to the output buffer of compare to the input buffer).
Unfortunately, this change was made only for TLS 1.0 and later, leaving SSL
3.0 in an inconsistent state due to ssl_mac() still writing to the old,
hard-coded location, which, for MAC verification, resulted in later comparing
the end of the input buffer (containing the computed MAC) to the local buffer
(uninitialised), most likely resulting in MAC verification failure, hence no
interop (even with ourselves).
This commit completes the move to using a local buffer by using this strategy
for SSL 3.0 too. Fortunately ssl_mac() was static so it's not a problem to
change its signature.
Fix the x509_get_subject_alt_name() function to not accept invalid
tags. The problem was that the ASN.1 class for tags consists of two
bits. Simply doing bit-wise and of the CONTEXT_SPECIFIC macro with the
input tag has the potential of accepting tag values 0x10 (private)
which would indicate that the certificate has an incorrect format.
In case truncated HMAC must be used but the Mbed TLS peer hasn't been updated
yet, one can use the compile-time option MBEDTLS_SSL_TRUNCATED_HMAC_COMPAT to
temporarily fall back to the old, non-compliant implementation of the truncated
HMAC extension.
The truncated HMAC extension as described in
https://tools.ietf.org/html/rfc6066.html#section-7 specifies that when truncated
HMAC is used, only the HMAC output should be truncated, while the HMAC key
generation stays unmodified. This commit fixes Mbed TLS's behavior of also
truncating the key, potentially leading to compatibility issues with peers
running other stacks than Mbed TLS.
Details:
The keys for the MAC are pieces of the keyblock that's generated from the
master secret in `mbedtls_ssl_derive_keys` through the PRF, their size being
specified as the size of the digest used for the MAC, regardless of whether
truncated HMAC is enabled or not.
/----- MD size ------\ /------- MD size ----\
Keyblock +----------------------+----------------------+------------------+---
now | MAC enc key | MAC dec key | Enc key | ...
(correct) +----------------------+----------------------+------------------+---
In the previous code, when truncated HMAC was enabled, the HMAC keys
were truncated to 10 bytes:
/-10 bytes-\ /-10 bytes-\
Keyblock +-------------+-------------+------------------+---
previously | MAC enc key | MAC dec key | Enc key | ...
(wrong) +-------------+-------------+------------------+---
The reason for this was that a single variable `transform->maclen` was used for
both the keysize and the size of the final MAC, and its value was reduced from
the MD size to 10 bytes in case truncated HMAC was negotiated.
This commit fixes this by introducing a temporary variable `mac_key_len` which
permanently holds the MD size irrespective of the presence of truncated HMAC,
and using this temporary to obtain the MAC key chunks from the keyblock.
Fix missing definition of mbedtls_zeroize when MBEDTLS_FS_IO is
disabled in the configuration.
Introduced by d08ae68237
Merge remote-tracking branch 'upstream-public/pr/1112' into mbedtls-2.1
Previously, MAC validation for an incoming record proceeded as follows:
1) Make a copy of the MAC contained in the record;
2) Compute the expected MAC in place, overwriting the presented one;
3) Compare both.
This resulted in a record buffer overflow if truncated MAC was used, as in this
case the record buffer only reserved 10 bytes for the MAC, but the MAC
computation routine in 2) always wrote a full digest.
For specially crafted records, this could be used to perform a controlled write of
up to 6 bytes past the boundary of the heap buffer holding the record, thereby
corrupting the heap structures and potentially leading to a crash or remote code
execution.
This commit fixes this by making the following change:
1) Compute the expected MAC in a temporary buffer that has the size of the
underlying message digest.
2) Compare to this to the MAC contained in the record, potentially
restricting to the first 10 bytes if truncated HMAC is used.
A similar fix is applied to the encryption routine `ssl_encrypt_buf`.
* mbedtls-2.1:
Fix typo in asn1.h
Improve leap year test names in x509parse.data
Correctly handle leap year in x509_date_is_valid()
Renegotiation: Add tests for SigAlg ext parsing
Parse Signature Algorithm ext when renegotiating
Fix changelog for ssl_server2.c usage fix
Fix ssl_server2 sample application prompt
Update ChangeLog for fix to #836
Enhance documentation of ssl_write_hostname_ext, adapt ChangeLog.
Enhance documentation of mbedtls_ssl_set_hostname
Add test case calling ssl_set_hostname twice
Make mbedtls_ssl_set_hostname safe to be called multiple times
Fix typo in configs/README.txt file
The function mbedtls_ecp_gen_keypair_base did not wipe the stack buffer used to
hold the private exponent before returning. This commit fixes this by not using
a stack buffer in the first place but instead calling mpi_fill_random directly
to acquire the necessary random MPI.
This commit modifies mpi_read_binary to always allocate the minimum number of
limbs required to hold the entire buffer provided to the function, regardless of
its content. Previously, leading zero bytes in the input data were detected and
used to reduce memory footprint and time, but this non-constant behavior turned
out to be non-tolerable for the cryptographic applications this function is used
for.
Previously, if `MBEDTLS_SSL_RENEGOTIATION` was disabled, incoming handshake
messages in `mbedtls_ssl_read` (expecting application data) lead to the
connection being closed. This commit fixes this, restricting the
`MBEDTLS_SSL_RENEGOTIATION`-guard to the code-paths responsible for accepting
renegotiation requests and aborting renegotiation attempts after too many
unexpected records have been received.
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.
This commit fixes a comparison of ssl_session->encrypt_then_mac against the
ETM-unrelated constant MBEDTLS_SSL_EXTENDED_MS_DISABLED. Instead,
MBEDTLS_SSL_ETM_DISABLED should be used.
The typo is has no functional effect since both constants have the same value 0.
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).
