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Merge remote-tracking branch 'origin/pr/2504' into mbedtls-2.7

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* origin/pr/2504:
  Fix ChangeLog entry ordering
  Fix typo
  Add non-regression test for buffer overflow
  Improve documentation of mbedtls_mpi_write_string()
  Adapt ChangeLog
  Fix 1-byte buffer overflow in mbedtls_mpi_write_string()
This commit is contained in:
Jaeden Amero 2019-04-05 14:09:25 +01:00
commit 99b679f364
4 changed files with 25 additions and 9 deletions
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2
ChangeLog
View File

@ -23,6 +23,8 @@ Bugfix
Christian Walther in #2239.
* Fix potential memory leak in X.509 self test. Found and fixed by
Junhwan Park, #2106.
* Fix 1-byte buffer overflow in mbedtls_mpi_write_string() when
used with negative inputs. Found by Guido Vranken in #2404.
Changes
* Return from various debugging routines immediately if the

26
library/bignum.c
View File

@ -552,15 +552,20 @@ int mbedtls_mpi_write_string( const mbedtls_mpi *X, int radix,
if( radix < 2 || radix > 16 )
return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
n = mbedtls_mpi_bitlen( X );
if( radix >= 4 ) n >>= 1;
if( radix >= 16 ) n >>= 1;
/*
* Round up the buffer length to an even value to ensure that there is
* enough room for hexadecimal values that can be represented in an odd
* number of digits.
*/
n += 3 + ( ( n + 1 ) & 1 );
n = mbedtls_mpi_bitlen( X ); /* Number of bits necessary to present `n`. */
if( radix >= 4 ) n >>= 1; /* Number of 4-adic digits necessary to present
* `n`. If radix > 4, this might be a strict
* overapproximation of the number of
* radix-adic digits needed to present `n`. */
if( radix >= 16 ) n >>= 1; /* Number of hexadecimal digits necessary to
* present `n`. */
n += 1; /* Terminating null byte */
n += 1; /* Compensate for the divisions above, which round down `n`
* in case it's not even. */
n += 1; /* Potential '-'-sign. */
n += ( n & 1 ); /* Make n even to have enough space for hexadecimal writing,
* which always uses an even number of hex-digits. */
if( buflen < n )
{
@ -572,7 +577,10 @@ int mbedtls_mpi_write_string( const mbedtls_mpi *X, int radix,
mbedtls_mpi_init( &T );
if( X->s == -1 )
{
*p++ = '-';
buflen--;
}
if( radix == 16 )
{

3
tests/suites/test_suite_mpi.data
View File

@ -19,6 +19,9 @@ mpi_read_write_string:16:"-20":10:"-32":100:0:0
Base test mpi_read_write_string #3 (Negative decimal)
mpi_read_write_string:16:"-23":16:"-23":100:0:0
Base test mpi_read_write_string #4 (Buffer just fits)
mpi_read_write_string:16:"-4":4:"-10":4:0:0
Test mpi_read_write_string #1 (Invalid character)
mpi_read_write_string:10:"a28":0:"":100:MBEDTLS_ERR_MPI_INVALID_CHARACTER:0

3
tests/suites/test_suite_mpi.function
View File

@ -81,6 +81,8 @@ void mpi_read_write_string( int radix_X, char *input_X, int radix_A,
mbedtls_mpi_init( &X );
memset( str, '!', sizeof( str ) );
TEST_ASSERT( mbedtls_mpi_read_string( &X, radix_X, input_X ) == result_read );
if( result_read == 0 )
{
@ -88,6 +90,7 @@ void mpi_read_write_string( int radix_X, char *input_X, int radix_A,
if( result_write == 0 )
{
TEST_ASSERT( strcasecmp( str, input_A ) == 0 );
TEST_ASSERT( str[len] == '!' );
}
}