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Merge pull request #3841 from AndrzejKurek/baremetal-rnd-in-range-fix

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Move size checks outside of mbedtls_platform_random_in_range
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Andrzej Kurek 2020-11-25 11:41:40 +01:00 committed by GitHub
parent 21f64d3633 a138c0a0b0
commit 5eba1d82a2
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 51 additions and 56 deletions
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4
include/mbedtls/platform_util.h
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@ -276,9 +276,9 @@ uint32_t mbedtls_platform_random_uint32( void );
* cryptographically secure RNG, but provide an RNG for utility * cryptographically secure RNG, but provide an RNG for utility
* functions. * functions.
* *
* \note If the given range is [0, 0), 0 is returned.
*
* \param num Max-value for the generated random number, exclusive. * \param num Max-value for the generated random number, exclusive.
* Must be greater than zero, otherwise an undefined behavior
* will occur on "num % 0".
* The generated number will be on range [0, num). * The generated number will be on range [0, num).
* *
* \return The generated random number. * \return The generated random number.

29
library/platform_util.c
View file

@ -119,12 +119,14 @@ void *mbedtls_platform_zeroize( void *buf, size_t len )
void *mbedtls_platform_memset( void *ptr, int value, size_t num ) void *mbedtls_platform_memset( void *ptr, int value, size_t num )
{ {
size_t i, start_offset; size_t i, start_offset = 0;
volatile size_t flow_counter = 0; volatile size_t flow_counter = 0;
volatile char *b = ptr; volatile char *b = ptr;
char rnd_data; char rnd_data;
if( num > 0 )
{
start_offset = (size_t) mbedtls_platform_random_in_range( (uint32_t) num ); start_offset = (size_t) mbedtls_platform_random_in_range( (uint32_t) num );
rnd_data = (char) mbedtls_platform_random_in_range( 256 ); rnd_data = (char) mbedtls_platform_random_in_range( 256 );
/* Perform a memset operations with random data and start from a random /* Perform a memset operations with random data and start from a random
@ -155,7 +157,7 @@ void *mbedtls_platform_memset( void *ptr, int value, size_t num )
b[i] = value; b[i] = value;
flow_counter++; flow_counter++;
} }
}
/* check the correct number of iterations */ /* check the correct number of iterations */
if( flow_counter == 2 * num ) if( flow_counter == 2 * num )
{ {
@ -165,6 +167,7 @@ void *mbedtls_platform_memset( void *ptr, int value, size_t num )
return ptr; return ptr;
} }
} }
return NULL; return NULL;
} }
@ -245,7 +248,10 @@ int mbedtls_platform_memequal( const void *buf1, const void *buf2, size_t num )
/* Start from a random location and check the correct number of iterations */ /* Start from a random location and check the correct number of iterations */
size_t i, flow_counter = 0; size_t i, flow_counter = 0;
size_t start_offset = (size_t) mbedtls_platform_random_in_range( (uint32_t) num ); size_t start_offset = 0;
if( num > 0 )
{
start_offset = (size_t) mbedtls_platform_random_in_range( (uint32_t) num );
for( i = start_offset; i < num; i++ ) for( i = start_offset; i < num; i++ )
{ {
@ -260,7 +266,7 @@ int mbedtls_platform_memequal( const void *buf1, const void *buf2, size_t num )
flow_counter++; flow_counter++;
diff |= x ^ y; diff |= x ^ y;
} }
}
/* Return 0 only when diff is 0 and flow_counter is equal to num */ /* Return 0 only when diff is 0 and flow_counter is equal to num */
return( (int) diff | (int) ( flow_counter ^ num ) ); return( (int) diff | (int) ( flow_counter ^ num ) );
} }
@ -340,18 +346,7 @@ void mbedtls_platform_random_buf( uint8_t *buf, size_t len )
uint32_t mbedtls_platform_random_in_range( uint32_t num ) uint32_t mbedtls_platform_random_in_range( uint32_t num )
{ {
uint32_t result; return mbedtls_platform_random_uint32() % num;
if( num <= 1 )
{
result = 0;
}
else
{
result = mbedtls_platform_random_uint32() % num;
}
return( result );
} }
void mbedtls_platform_random_delay( void ) void mbedtls_platform_random_delay( void )