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[crypto] Allow for zero-length big integer literals

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Ensure that zero-length big integer literals are treated as containing
a zero value.  Avoid tests on every big integer arithmetic operation
by ensuring that bigint_required_size() always returns a non-zero
value: the zero-length tests can therefore be restricted to only
bigint_init() and bigint_done().

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2025-12-29 14:01:46 +00:00
parent 01038893a3
commit 7c39c04a53
3 changed files with 15 additions and 4 deletions
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8
src/arch/x86/include/bits/bigint.h
View File

@@ -32,10 +32,12 @@ bigint_init_raw ( uint32_t *value0, unsigned int size,
long discard_c; long discard_c;
/* Copy raw data in reverse order, padding with zeros */ /* Copy raw data in reverse order, padding with zeros */
__asm__ __volatile__ ( "\n1:\n\t" __asm__ __volatile__ ( "jecxz 2f\n\t"
"\n1:\n\t"
"movb -1(%3,%1), %%al\n\t" "movb -1(%3,%1), %%al\n\t"
"stosb\n\t" "stosb\n\t"
"loop 1b\n\t" "loop 1b\n\t"
"\n2:\n\t"
"xorl %%eax, %%eax\n\t" "xorl %%eax, %%eax\n\t"
"mov %4, %1\n\t" "mov %4, %1\n\t"
"rep stosb\n\t" "rep stosb\n\t"
@@ -308,10 +310,12 @@ bigint_done_raw ( const uint32_t *value0, unsigned int size __unused,
long discard_c; long discard_c;
/* Copy raw data in reverse order */ /* Copy raw data in reverse order */
__asm__ __volatile__ ( "\n1:\n\t" __asm__ __volatile__ ( "jecxz 2f\n\t"
"\n1:\n\t"
"movb -1(%3,%1), %%al\n\t" "movb -1(%3,%1), %%al\n\t"
"stosb\n\t" "stosb\n\t"
"loop 1b\n\t" "loop 1b\n\t"
"\n2:\n\t"
: "=&D" ( discard_D ), "=&c" ( discard_c ), : "=&D" ( discard_D ), "=&c" ( discard_c ),
"+m" ( *out_bytes ) "+m" ( *out_bytes )
: "r" ( value0 ), "0" ( out ), "1" ( len ) : "r" ( value0 ), "0" ( out ), "1" ( len )

4
src/include/ipxe/bigint.h
View File

@@ -28,8 +28,8 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
* @ret size Number of elements * @ret size Number of elements
*/ */
#define bigint_required_size( len ) \ #define bigint_required_size( len ) \
( ( (len) + sizeof ( bigint_element_t ) - 1 ) / \ ( (len) ? ( ( (len) + sizeof ( bigint_element_t ) - 1 ) / \
sizeof ( bigint_element_t ) ) sizeof ( bigint_element_t ) ) : 1 )
/** /**
* Determine number of elements in big-integer type * Determine number of elements in big-integer type

7
src/tests/bigint_test.c
View File

@@ -841,6 +841,7 @@ static void bigint_mod_exp_okx ( struct bigint_test *base,
*/ */
static void bigint_test_exec ( void ) { static void bigint_test_exec ( void ) {
bigint_add_ok ( BIGINT(), BIGINT(), BIGINT(), 0 );
bigint_add_ok ( BIGINT ( 0x8a ), bigint_add_ok ( BIGINT ( 0x8a ),
BIGINT ( 0x43 ), BIGINT ( 0x43 ),
BIGINT ( 0xcd ), 0 ); BIGINT ( 0xcd ), 0 );
@@ -934,6 +935,7 @@ static void bigint_test_exec ( void ) {
0x9f, 0x60, 0x58, 0xff, 0xb6, 0x76, 0x45, 0x9f, 0x60, 0x58, 0xff, 0xb6, 0x76, 0x45,
0xe6, 0xed, 0x61, 0x8d, 0xe6, 0xc0, 0x72, 0xe6, 0xed, 0x61, 0x8d, 0xe6, 0xc0, 0x72,
0x1c, 0x07 ), 0 ); 0x1c, 0x07 ), 0 );
bigint_subtract_ok ( BIGINT(), BIGINT(), BIGINT(), 0 );
bigint_subtract_ok ( BIGINT ( 0x83 ), bigint_subtract_ok ( BIGINT ( 0x83 ),
BIGINT ( 0x50 ), BIGINT ( 0x50 ),
BIGINT ( 0xcd ), 1 ); BIGINT ( 0xcd ), 1 );
@@ -1033,6 +1035,7 @@ static void bigint_test_exec ( void ) {
0xda, 0xc8, 0x8c, 0x71, 0x86, 0x97, 0xda, 0xc8, 0x8c, 0x71, 0x86, 0x97,
0x7f, 0xcb, 0x94, 0x31, 0x1d, 0xbc, 0x7f, 0xcb, 0x94, 0x31, 0x1d, 0xbc,
0x44, 0x1a ), 0 ); 0x44, 0x1a ), 0 );
bigint_shl_ok ( BIGINT(), BIGINT(), 0 );
bigint_shl_ok ( BIGINT ( 0xe0 ), bigint_shl_ok ( BIGINT ( 0xe0 ),
BIGINT ( 0xc0 ), 1 ); BIGINT ( 0xc0 ), 1 );
bigint_shl_ok ( BIGINT ( 0x43, 0x1d ), bigint_shl_ok ( BIGINT ( 0x43, 0x1d ),
@@ -1099,6 +1102,7 @@ static void bigint_test_exec ( void ) {
0x49, 0x7c, 0x1e, 0xdb, 0xc7, 0x65, 0xa6, 0x49, 0x7c, 0x1e, 0xdb, 0xc7, 0x65, 0xa6,
0x0e, 0xd1, 0xd2, 0x00, 0xb3, 0x41, 0xc9, 0x0e, 0xd1, 0xd2, 0x00, 0xb3, 0x41, 0xc9,
0x3c, 0xbc ), 0 ); 0x3c, 0xbc ), 0 );
bigint_shr_ok ( BIGINT(), BIGINT(), 0 );
bigint_shr_ok ( BIGINT ( 0x8f ), bigint_shr_ok ( BIGINT ( 0x8f ),
BIGINT ( 0x47 ), 1 ); BIGINT ( 0x47 ), 1 );
bigint_shr_ok ( BIGINT ( 0xaa, 0x1d ), bigint_shr_ok ( BIGINT ( 0xaa, 0x1d ),
@@ -1165,6 +1169,7 @@ static void bigint_test_exec ( void ) {
0x46, 0xa8, 0x94, 0xb0, 0xf7, 0xa4, 0x57, 0x46, 0xa8, 0x94, 0xb0, 0xf7, 0xa4, 0x57,
0x1f, 0x72, 0x88, 0x5f, 0xed, 0x4d, 0xc9, 0x1f, 0x72, 0x88, 0x5f, 0xed, 0x4d, 0xc9,
0x59, 0xbb ), 1 ); 0x59, 0xbb ), 1 );
bigint_is_zero_ok ( BIGINT(), 1 );
bigint_is_zero_ok ( BIGINT ( 0x9b ), bigint_is_zero_ok ( BIGINT ( 0x9b ),
0 ); 0 );
bigint_is_zero_ok ( BIGINT ( 0x5a, 0x9d ), bigint_is_zero_ok ( BIGINT ( 0x5a, 0x9d ),
@@ -1273,6 +1278,7 @@ static void bigint_test_exec ( void ) {
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff ), 0xff, 0xff ),
0 ); 0 );
bigint_is_geq_ok ( BIGINT(), BIGINT(), 1 );
bigint_is_geq_ok ( BIGINT ( 0xa2 ), bigint_is_geq_ok ( BIGINT ( 0xa2 ),
BIGINT ( 0x58 ), BIGINT ( 0x58 ),
1 ); 1 );
@@ -1540,6 +1546,7 @@ static void bigint_test_exec ( void ) {
0x83, 0xf8, 0xa2, 0x11, 0xf5, 0xd4, 0x83, 0xf8, 0xa2, 0x11, 0xf5, 0xd4,
0xcb, 0xe0 ), 0xcb, 0xe0 ),
1013, 0 ); 1013, 0 );
bigint_max_set_bit_ok ( BIGINT(), 0 );
bigint_max_set_bit_ok ( BIGINT ( 0x3a ), bigint_max_set_bit_ok ( BIGINT ( 0x3a ),
6 ); 6 );
bigint_max_set_bit_ok ( BIGINT ( 0x03 ), bigint_max_set_bit_ok ( BIGINT ( 0x03 ),