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214 commits

Author SHA1 Message Date
Bence Szépkúti a2947ac7bb Update copyright notices to use Linux Foundation guidance
As a result, the copyright of contributors other than Arm is now
acknowledged, and the years of publishing are no longer tracked in the
source files.

Also remove the now-redundant lines declaring that the files are part of
MbedTLS.

This commit was generated using the following script:

# ========================
#!/bin/sh

# Find files
find '(' -path './.git' -o -path './3rdparty' ')' -prune -o -type f -print | xargs sed -bi '

# Replace copyright attribution line
s/Copyright.*Arm.*/Copyright The Mbed TLS Contributors/I

# Remove redundant declaration and the preceding line
$!N
/This file is part of Mbed TLS/Id
P
D
'
# ========================

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
2020-08-19 16:37:36 +02:00
Bence Szépkúti f744bd72ee Update license headers to Apache-2.0 OR GPL-2.0-or-later
This will allow us to ship the LTS branches in a single archive

This commit was generated using the following script:

# ========================
#!/bin/sh

header1='\ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later\
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 *  **********'

find -path './.git' -prune -o '(' -name '*.c' -o -name '*.cpp' -o -name '*.fmt' -o -name '*.h' ')' -print | xargs sed -i "
# Normalize the first line of the copyright headers (no text on the first line of a block comment)
/^\/\*.*Copyright.*Arm/I s/\/\*/&\n */

# Insert new copyright header
/SPDX-License-Identifier/ i\
$header1

# Delete old copyright header
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# Format copyright header for inclusion into scripts
header2=$(echo "$header1" | sed 's/^\\\? \* \?/#/')

find -path './.git' -prune -o '(' -name '*.gdb' -o -name '*.pl' -o -name '*.py' -o -name '*.sh' ')' -print | xargs sed -i "
# Insert new copyright header
/SPDX-License-Identifier/ i\
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# Delete old copyright header
/SPDX-License-Identifier/,$ {
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  N
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# ========================

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
2020-06-15 12:48:48 +02:00
Gilles Peskine de719d5d69 Clean up some comments
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 08fd43c4f6 mbedtls_mpi_sub_abs: check the range of the result when it happens
The function mbedtls_mpi_sub_abs first checked that A >= B and then
performed the subtraction, relying on the fact that A >= B to
guarantee that the carry propagation would stop, and not taking
advantage of the fact that the carry when subtracting two numbers can
only be 0 or 1. This made the carry propagation code a little hard to
follow.

Write an ad hoc loop for the carry propagation, checking the size of
the result. This makes termination obvious.

The initial check that A >= B is no longer needed, since the function
now checks that the carry propagation terminates, which is equivalent.
This is a slight performance gain.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 635a374944 Simplify the final reduction in mpi_montmul
There was some confusion during review about when A->p[n] could be
nonzero. In fact, there is no need to set A->p[n]: only the
intermediate result d might need to extend to n+1 limbs, not the final
result A. So never access A->p[n]. Rework the explanation of the
calculation in a way that should be easier to follow.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 36acd547c5 Move carry propagation out of mpi_sub_hlp
The function mpi_sub_hlp had confusing semantics: although it took a
size parameter, it accessed the limb array d beyond this size, to
propagate the carry. This made the function difficult to understand
and analyze, with a potential buffer overflow if misused (not enough
room to propagate the carry).

Change the function so that it only performs the subtraction within
the specified number of limbs, and returns the carry.

Move the carry propagation out of mpi_sub_hlp and into its caller
mbedtls_mpi_sub_abs. This makes the code of subtraction very slightly
less neat, but not significantly different.

In the one other place where mpi_sub_hlp is used, namely mpi_montmul,
this is a net win because the carry is potentially sensitive data and
the function carefully arranges to not have to propagate it.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 46bf7da684 More logical parameter order for mpi_sub_hlp
mpi_sub_hlp performs a subtraction A - B, but took parameters in the
order (B, A). Swap the parameters so that they match the usual
mathematical syntax.

This has the additional benefit of putting the output parameter (A)
first, which is the normal convention in this module.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 6a9433ef34 Explicitly cast down from mbedtls_mpi_uint to unsigned char
Let code analyzers know that this is deliberate. For example MSVC
warns about the conversion if it's implicit.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 8f6726623a Remove a secret-dependent branch in Montgomery multiplication
In mpi_montmul, an auxiliary function for modular
exponentiation (mbedtls_mpi_mod_exp) that performs Montgomery
multiplication, the last step is a conditional subtraction to force
the result into the correct range. The current implementation uses a
branch and therefore may leak information about secret data to an
adversary who can observe what branch is taken through a side channel.

Avoid this potential leak by always doing the same subtraction and
doing a contant-trace conditional assignment to set the result.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine c81c5889e9 Separate out low-level mpi_safe_cond_assign
Separate out a version of mpi_safe_cond_assign that works on
equal-sized limb arrays, without worrying about allocation sizes or
signs.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 3ce3ddf1ac Document some internal bignum functions
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine bdcb39616d Revert "Shut up a clang-analyzer warning"
This reverts commit 2cc69fffcf.

A check was added in mpi_montmul because clang-analyzer warned about a
possibly null pointer. However this was a false positive. Recent
versions of clang-analyzer no longer emit a warning (3.6 does, 6
doesn't).

Incidentally, the size check was wrong: mpi_montmul needs
T->n >= 2 * (N->n + 1), not just T->n >= N->n + 1.

Given that this is an internal function which is only used from one
public function and in a tightly controlled way, remove both the null
check (which is of low value to begin with) and the size check (which
would be slightly more valuable, but was wrong anyway). This allows
the function not to need to return an error, which makes the source
code a little easier to read and makes the object code a little
smaller.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine e9073a6cb2 Add a const annotation to the non-changing argument of mpi_sub_mul
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2020-06-09 11:31:30 +02:00
Gilles Peskine 56427c2d2b Minor comment improvement 2020-02-03 16:21:31 +01:00
Gilles Peskine 27c15c7853 Improve comments in mpi_shrink 2020-02-03 16:21:31 +01:00
Gilles Peskine 3e9f5228c8 mpi_copy: make the 0 case slightly more robust
If Y was constructed through functions in this module, then Y->n == 0
iff Y->p == NULL. However we do not prevent filling mpi structures
manually, and zero may be represented with n=0 and p a valid pointer.
Most of the code can cope with such a representation, but for the
source of mbedtls_mpi_copy, this would cause an integer underflow.
Changing the test for zero from Y->p==NULL to Y->n==0 causes this case
to work at no extra cost.
2020-02-03 16:21:31 +01:00
Janos Follath e25f1ee44d mpi_lt_mpi_ct: fix condition handling
The code previously only set the done flag if the return value was one.
This led to overriding the correct return value later on.
2019-11-11 12:32:12 +00:00
Janos Follath 359a01e07c ct_lt_mpi_uint: cast the return value explicitely
The return value is always either one or zero and therefore there is no
risk of losing precision. Some compilers can't deduce this and complain.
2019-11-11 12:32:12 +00:00
Janos Follath fbe4c947cd mbedtls_mpi_lt_mpi_ct: simplify condition
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.
2019-11-11 12:32:12 +00:00
Janos Follath 1f21c1d519 Rename variable for better readability 2019-11-11 12:32:12 +00:00
Janos Follath bd87a59007 mbedtls_mpi_lt_mpi_ct: Improve documentation 2019-11-11 12:32:12 +00:00
Janos Follath 58525180fb Make mbedtls_mpi_lt_mpi_ct more portable
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.
2019-11-11 12:32:12 +00:00
Janos Follath 45ec990711 Document ct_lt_mpi_uint 2019-11-11 12:32:12 +00:00
Janos Follath b11ce0ec2d mpi_lt_mpi_ct: make use of unsigned consistent 2019-11-11 12:32:12 +00:00
Janos Follath 7a34bcffef ct_lt_mpi_uint: make use of biL 2019-11-11 12:32:12 +00:00
Janos Follath 867a3abff5 Change mbedtls_mpi_cmp_mpi_ct to check less than
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.
2019-11-11 12:32:12 +00:00
Janos Follath 4f6cf38016 mbedtls_mpi_cmp_mpi_ct: remove multiplications
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.
2019-11-11 12:32:12 +00:00
Janos Follath 4ea2319726 Remove declaration after statement
Visual Studio 2013 does not like it for some reason.
2019-11-11 12:32:12 +00:00
Janos Follath b9f6f9bc97 Add new, constant time mpi comparison 2019-11-11 12:32:12 +00:00
Jaeden Amero da5930654e Merge remote-tracking branch 'origin/pr/2578' into mbedtls-2.16
* origin/pr/2578:
  Remove a redundant function call
2019-10-02 17:59:28 +01:00
Jaeden Amero c3bfb20a41 Merge remote-tracking branch 'origin/pr/2645' into mbedtls-2.16
* origin/pr/2645:
  Adapt ChangeLog
  Fix mpi_bigendian_to_host() on bigendian systems
2019-09-05 17:37:13 +01:00
Jaeden Amero adb4fa5921 Merge remote-tracking branch 'origin/pr/2398' into mbedtls-2.16
* origin/pr/2398:
  Add ChangeLog entry
  fix memory leak in mpi_miller_rabin()
2019-09-03 16:32:54 +01:00
Hanno Becker 92c98931f2 Fix mpi_bigendian_to_host() on bigendian systems
The previous implementation of mpi_bigendian_to_host() did
a byte-swapping regardless of the endianness of the system.

Fixes #2622.
2019-05-15 13:12:29 +01:00
Ron Eldor ff8d8d72aa Remove a redundant function call
Remove a call to `mbedtls_mpi_bitlen()` since the returned value is
overwritten in the line after. This is redundant since da31fa137a.
Fixes #2377.
2019-05-01 17:13:48 +03:00
Janos Follath 870ed0008a Fix typo 2019-03-06 13:51:30 +00:00
Hanno Becker c1fa6cdab6 Improve documentation of mbedtls_mpi_write_string() 2019-03-06 13:51:19 +00:00
Hanno Becker af97cae27d Fix 1-byte buffer overflow in mbedtls_mpi_write_string()
This can only occur for negative numbers. Fixes #2404.
2019-03-06 13:50:54 +00:00
Peter Kolbus b83d41d828 Fix DEADCODE in mbedtls_mpi_exp_mod()
In mbedtls_mpi_exp_mod(), the limit check on wsize is never true when
MBEDTLS_MPI_WINDOW_SIZE is at least 6. Wrap in a preprocessor guard
to remove the dead code and resolve a Coverity finding from the
DEADCODE checker.

Change-Id: Ice7739031a9e8249283a04de11150565b613ae89
2019-02-05 16:44:03 +01:00
Jens Wiklander dfd447e836 fix memory leak in mpi_miller_rabin()
Fixes memory leak in mpi_miller_rabin() that occurs when the function has
failed to obtain a usable random 'A' 30 turns in a row.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
2019-01-31 19:09:17 +02:00
Jaeden Amero 4002ada9f3 Merge remote-tracking branch 'origin/pr/2214' into mbedtls-2.16 2019-01-30 15:03:02 +00:00
Hanno Becker 0e810b9648 Don't call memcpy with NULL pointer in mbedtls_mpi_read_binary()
mbedtls_mpi_read_binary() calls memcpy() with the source pointer being
the source pointer passed to mbedtls_mpi_read_binary(), the latter may
be NULL if the buffer length is 0 (and this happens e.g. in the ECJPAKE
test suite). The behavior of memcpy(), in contrast, is undefined when
called with NULL source buffer, even if the length of the copy operation
is 0.

This commit fixes this by explicitly checking that the source pointer is
not NULL before calling memcpy(), and skipping the call otherwise.
2019-01-03 17:13:11 +00:00
Hanno Becker 9f6d16ad79 Fix preprocessor macro existence check in bignum.c 2019-01-02 17:15:06 +00:00
Hanno Becker 6dab6200c6 Fix typo after rebase 2019-01-02 16:42:29 +00:00
Hanno Becker 5d91c0bbee Add missing macro existence check in byte swapping code in bignum.c 2019-01-02 11:38:14 +00:00
Hanno Becker f872007782 Optimize mpi_bigendian_to_host() for speed and size
Use GCC / Clang builtins for byte swapping.
2019-01-02 11:38:14 +00:00
Hanno Becker 2be8a55f72 Change signature of mpi_bigendian_to_host() to reflect usage 2019-01-02 11:37:25 +00:00
Hanno Becker da1655a48e Remove temporary stack-buffer from mbedtls_mpi_fill_random()
Context: The function `mbedtls_mpi_fill_random()` uses a temporary stack
buffer to hold the random data before reading it into the target MPI.

Problem: This is inefficient both computationally and memory-wise.
Memory-wise, it may lead to a stack overflow on constrained devices with
limited stack.

Fix: This commit introduces the following changes to get rid of the
temporary stack buffer entirely:

1. It modifies the call to the PRNG to output the random data directly
   into the target MPI's data buffer.

This alone, however, constitutes a change of observable behaviour:
The previous implementation guaranteed to interpret the bytes emitted by
the PRNG in a big-endian fashion, while rerouting the PRNG output into the
target MPI's limb array leads to an interpretation that depends on the
endianness of the host machine.
As a remedy, the following change is applied, too:

2. Reorder the bytes emitted from the PRNG within the target MPI's
   data buffer to ensure big-endian semantics.

Luckily, the byte reordering was already implemented as part of
`mbedtls_mpi_read_binary()`, so:

3. Extract bigendian-to-host byte reordering from
   `mbedtls_mpi_read_binary()` to a separate internal function
   `mpi_bigendian_to_host()` to be used by `mbedtls_mpi_read_binary()`
   and `mbedtls_mpi_fill_random()`.
2019-01-02 11:37:25 +00:00
Hanno Becker f25ee7f79d Fix parameter validation for mbedtls_mpi_lsb()
The MPI_VALIDATE_RET() macro cannot be used for parameter
validation of mbedtls_mpi_lsb() because this function returns
a size_t.

Use the underlying MBEDTLS_INTERNAL_VALIDATE_RET() insteaed,
returning 0 on failure.

Also, add a test for this behaviour.
2018-12-19 16:51:50 +00:00
Hanno Becker 8ce11a323e Minor improvements to bignum module 2018-12-19 16:18:52 +00:00
Hanno Becker 54c91dd235 Remove double semicolon from bignum.c 2018-12-18 18:12:13 +00:00