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Merge pull request #293 from gilles-peskine-arm/entropy-min

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Always gather MBEDTLS_ENTROPY_BLOCK_SIZE bytes of entropy
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Gilles Peskine 2019-11-26 18:43:45 +01:00 committed by GitHub
commit 8f4df81506
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 151 additions and 41 deletions
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14
library/entropy.c
View file

@ -327,7 +327,8 @@ int mbedtls_entropy_gather( mbedtls_entropy_context *ctx )
int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
{
int ret, count = 0, i, done;
int ret, count = 0, i, thresholds_reached;
size_t strong_size;
mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
@ -365,12 +366,17 @@ int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
goto exit;
done = 1;
thresholds_reached = 1;
strong_size = 0;
for( i = 0; i < ctx->source_count; i++ )
{
if( ctx->source[i].size < ctx->source[i].threshold )
done = 0;
thresholds_reached = 0;
if( ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG )
strong_size += ctx->source[i].size;
}
}
while( ! done );
while( ! thresholds_reached || strong_size < MBEDTLS_ENTROPY_BLOCK_SIZE );
memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );

43
tests/suites/test_suite_entropy.data
View file

@ -1,45 +1,66 @@
Create NV seed_file
nv_seed_file_create:
Entropy write/update seed file [#1]
Entropy write/update seed file: good
entropy_seed_file:"data_files/entropy_seed":0
Entropy write/update seed file [#2]
Entropy write/update seed file: nonexistent
entropy_seed_file:"no_such_dir/file":MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR
Entropy no sources
entropy_no_sources:
Entropy too many sources
entropy_too_many_sources:
Entropy output length #1
Entropy output length: 0
entropy_func_len:0:0
Entropy output length #2
Entropy output length: 1
entropy_func_len:1:0
Entropy output length #3
Entropy output length: 2
entropy_func_len:2:0
Entropy output length #4
Entropy output length: 31
entropy_func_len:31:0
Entropy output length #5
Entropy output length: 65 > BLOCK_SIZE
entropy_func_len:65:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
Entropy failing source
entropy_source_fail:"data_files/entropy_seed"
Entropy threshold #1
Entropy threshold: 16=2*8
entropy_threshold:16:2:8
Entropy threshold #2
Entropy threshold: 32=1*32
entropy_threshold:32:1:32
Entropy threshold #3
Entropy threshold: 0* never reaches the threshold
entropy_threshold:16:0:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
Entropy threshold #4
Entropy threshold: 1024 never reached
entropy_threshold:1024:1:MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
Entropy calls: no strong
entropy_calls:MBEDTLS_ENTROPY_SOURCE_WEAK:MBEDTLS_ENTROPY_SOURCE_WEAK:1:MBEDTLS_ENTROPY_BLOCK_SIZE:MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE
Entropy calls: 1 strong, 1*BLOCK_SIZE
entropy_calls:MBEDTLS_ENTROPY_SOURCE_STRONG:MBEDTLS_ENTROPY_SOURCE_WEAK:1:MBEDTLS_ENTROPY_BLOCK_SIZE:1
Entropy calls: 1 strong, 2*(BLOCK_SIZE/2)
entropy_calls:MBEDTLS_ENTROPY_SOURCE_STRONG:MBEDTLS_ENTROPY_SOURCE_WEAK:1:(MBEDTLS_ENTROPY_BLOCK_SIZE+1)/2:2
Entropy calls: 1 strong, BLOCK_SIZE*1
entropy_calls:MBEDTLS_ENTROPY_SOURCE_STRONG:MBEDTLS_ENTROPY_SOURCE_WEAK:1:1:MBEDTLS_ENTROPY_BLOCK_SIZE
Entropy calls: 1 strong, 2*BLOCK_SIZE to reach threshold
entropy_calls:MBEDTLS_ENTROPY_SOURCE_STRONG:MBEDTLS_ENTROPY_SOURCE_WEAK:MBEDTLS_ENTROPY_BLOCK_SIZE+1:MBEDTLS_ENTROPY_BLOCK_SIZE:2
Entropy calls: 2 strong, BLOCK_SIZE/2 each
entropy_calls:MBEDTLS_ENTROPY_SOURCE_STRONG:MBEDTLS_ENTROPY_SOURCE_WEAK:(MBEDTLS_ENTROPY_BLOCK_SIZE+1)/2:(MBEDTLS_ENTROPY_BLOCK_SIZE+1)/2:2
Check NV seed standard IO
entropy_nv_seed_std_io:

135
tests/suites/test_suite_entropy.function
View file

@ -3,10 +3,19 @@
#include "mbedtls/entropy_poll.h"
#include "string.h"
/*
* Number of calls made to entropy_dummy_source()
*/
static size_t entropy_dummy_calls;
typedef enum
{
DUMMY_CONSTANT_LENGTH, /* Output context->length bytes */
DUMMY_REQUESTED_LENGTH, /* Output whatever length was requested */
DUMMY_FAIL, /* Return an error code */
} entropy_dummy_instruction;
typedef struct
{
entropy_dummy_instruction instruction;
size_t length; /* Length to return for DUMMY_CONSTANT_LENGTH */
size_t calls; /* Incremented at each call */
} entropy_dummy_context;
/*
* Dummy entropy source
@ -14,29 +23,28 @@ static size_t entropy_dummy_calls;
* If data is NULL, write exactly the requested length.
* Otherwise, write the length indicated by data or error if negative
*/
static int entropy_dummy_source( void *data, unsigned char *output,
static int entropy_dummy_source( void *arg, unsigned char *output,
size_t len, size_t *olen )
{
entropy_dummy_calls++;
entropy_dummy_context *context = arg;
++context->calls;
if( data == NULL )
*olen = len;
else
switch( context->instruction )
{
int *d = (int *) data;
if( *d < 0 )
case DUMMY_CONSTANT_LENGTH:
*olen = context->length;
break;
case DUMMY_REQUESTED_LENGTH:
*olen = len;
break;
case DUMMY_FAIL:
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
else
*olen = *d;
}
memset( output, 0x2a, *olen );
return( 0 );
}
#if defined(MBEDTLS_ENTROPY_NV_SEED)
/*
* Ability to clear entropy sources to allow testing with just predefined
* entropy sources. This function or tests depending on it might break if there
@ -48,11 +56,12 @@ static int entropy_dummy_source( void *data, unsigned char *output,
* This might break memory checks in the future if sources need 'free-ing' then
* as well.
*/
void entropy_clear_sources( mbedtls_entropy_context *ctx )
static void entropy_clear_sources( mbedtls_entropy_context *ctx )
{
ctx->source_count = 0;
}
#if defined(MBEDTLS_ENTROPY_NV_SEED)
/*
* NV seed read/write functions that use a buffer instead of a file
*/
@ -139,11 +148,28 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE */
void entropy_no_sources( )
{
mbedtls_entropy_context ctx;
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
mbedtls_entropy_init( &ctx );
entropy_clear_sources( &ctx );
TEST_EQUAL( mbedtls_entropy_func( &ctx, buf, sizeof( buf ) ),
MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED );
exit:
mbedtls_entropy_free( &ctx );
}
/* END_CASE */
/* BEGIN_CASE */
void entropy_too_many_sources( )
{
mbedtls_entropy_context ctx;
size_t i;
entropy_dummy_context dummy = {DUMMY_REQUESTED_LENGTH, 0, 0};
mbedtls_entropy_init( &ctx );
@ -152,10 +178,10 @@ void entropy_too_many_sources( )
* since we don't know how many sources were automatically added.
*/
for( i = 0; i < MBEDTLS_ENTROPY_MAX_SOURCES; i++ )
(void) mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL,
(void) mbedtls_entropy_add_source( &ctx, entropy_dummy_source, &dummy,
16, MBEDTLS_ENTROPY_SOURCE_WEAK );
TEST_ASSERT( mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL,
TEST_ASSERT( mbedtls_entropy_add_source( &ctx, entropy_dummy_source, &dummy,
16, MBEDTLS_ENTROPY_SOURCE_WEAK )
== MBEDTLS_ERR_ENTROPY_MAX_SOURCES );
@ -197,13 +223,13 @@ void entropy_func_len( int len, int ret )
void entropy_source_fail( char * path )
{
mbedtls_entropy_context ctx;
int fail = -1;
unsigned char buf[16];
entropy_dummy_context dummy = {DUMMY_FAIL, 0, 0};
mbedtls_entropy_init( &ctx );
TEST_ASSERT( mbedtls_entropy_add_source( &ctx, entropy_dummy_source,
&fail, 16,
&dummy, 16,
MBEDTLS_ENTROPY_SOURCE_WEAK )
== 0 );
@ -225,30 +251,87 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE depends_on:ENTROPY_HAVE_STRONG */
/* BEGIN_CASE */
void entropy_threshold( int threshold, int chunk_size, int result )
{
mbedtls_entropy_context ctx;
entropy_dummy_context strong =
{DUMMY_CONSTANT_LENGTH, MBEDTLS_ENTROPY_BLOCK_SIZE, 0};
entropy_dummy_context weak = {DUMMY_CONSTANT_LENGTH, chunk_size, 0};
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
int ret;
mbedtls_entropy_init( &ctx );
entropy_clear_sources( &ctx );
/* Set strong source that reaches its threshold immediately and
* a weak source whose threshold is a test parameter. */
TEST_ASSERT( mbedtls_entropy_add_source( &ctx, entropy_dummy_source,
&chunk_size, threshold,
&strong, 1,
MBEDTLS_ENTROPY_SOURCE_STRONG ) == 0 );
TEST_ASSERT( mbedtls_entropy_add_source( &ctx, entropy_dummy_source,
&weak, threshold,
MBEDTLS_ENTROPY_SOURCE_WEAK ) == 0 );
entropy_dummy_calls = 0;
ret = mbedtls_entropy_func( &ctx, buf, sizeof( buf ) );
if( result >= 0 )
{
TEST_ASSERT( ret == 0 );
#if defined(MBEDTLS_ENTROPY_NV_SEED)
// Two times as much calls due to the NV seed update
/* If the NV seed functionality is enabled, there are two entropy
* updates: before and after updating the NV seed. */
result *= 2;
#endif
TEST_ASSERT( entropy_dummy_calls == (size_t) result );
TEST_ASSERT( weak.calls == (size_t) result );
}
else
{
TEST_ASSERT( ret == result );
}
exit:
mbedtls_entropy_free( &ctx );
}
/* END_CASE */
/* BEGIN_CASE */
void entropy_calls( int strength1, int strength2,
int threshold, int chunk_size,
int result )
{
/*
* if result >= 0: result = expected number of calls to source 1
* if result < 0: result = expected return code from mbedtls_entropy_func()
*/
mbedtls_entropy_context ctx;
entropy_dummy_context dummy1 = {DUMMY_CONSTANT_LENGTH, chunk_size, 0};
entropy_dummy_context dummy2 = {DUMMY_CONSTANT_LENGTH, chunk_size, 0};
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
int ret;
mbedtls_entropy_init( &ctx );
entropy_clear_sources( &ctx );
TEST_ASSERT( mbedtls_entropy_add_source( &ctx, entropy_dummy_source,
&dummy1, threshold,
strength1 ) == 0 );
TEST_ASSERT( mbedtls_entropy_add_source( &ctx, entropy_dummy_source,
&dummy2, threshold,
strength2 ) == 0 );
ret = mbedtls_entropy_func( &ctx, buf, sizeof( buf ) );
if( result >= 0 )
{
TEST_ASSERT( ret == 0 );
#if defined(MBEDTLS_ENTROPY_NV_SEED)
/* If the NV seed functionality is enabled, there are two entropy
* updates: before and after updating the NV seed. */
result *= 2;
#endif
TEST_ASSERT( dummy1.calls == (size_t) result );
}
else
{