[crypto] Allow for zero-length big integer literals

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>

diff --git a/src/arch/x86/include/bits/bigint.h b/src/arch/x86/include/bits/bigint.h
index 4bab3ebf7120ddb9c270aef7fdbe4d8e8710fe49..c6f097a34ed28ee09a1e04652331caa0851ea766 100644 (file)
--- a/src/arch/x86/include/bits/bigint.h
+++ b/src/arch/x86/include/bits/bigint.h
@@ -32,10 +32,12 @@ bigint_init_raw ( uint32_t *value0, unsigned int size,
        long discard_c;
 
        /* 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"
                               "stosb\n\t"
                               "loop 1b\n\t"
+                              "\n2:\n\t"
                               "xorl %%eax, %%eax\n\t"
                               "mov %4, %1\n\t"
                               "rep stosb\n\t"
@@ -308,10 +310,12 @@ bigint_done_raw ( const uint32_t *value0, unsigned int size __unused,
        long discard_c;
 
        /* 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"
                               "stosb\n\t"
                               "loop 1b\n\t"
+                              "\n2:\n\t"
                               : "=&D" ( discard_D ), "=&c" ( discard_c ),
                                 "+m" ( *out_bytes )
                               : "r" ( value0 ), "0" ( out ), "1" ( len )

diff --git a/src/include/ipxe/bigint.h b/src/include/ipxe/bigint.h
index 396462f3370d66dbfdf22d9729e394ae544c73ba..9eab89d25798a940f9527aea4f568e43ff476950 100644 (file)
--- a/src/include/ipxe/bigint.h
+++ b/src/include/ipxe/bigint.h
@@ -28,8 +28,8 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  * @ret size           Number of elements
  */
 #define bigint_required_size( len )                                    \
-       ( ( (len) + sizeof ( bigint_element_t ) - 1 ) /                 \
-         sizeof ( bigint_element_t ) )
+       ( (len) ? ( ( (len) + sizeof ( bigint_element_t ) - 1 ) /       \
+                   sizeof ( bigint_element_t ) ) : 1 )
 
 /**
  * Determine number of elements in big-integer type

diff --git a/src/tests/bigint_test.c b/src/tests/bigint_test.c
index 4090494ae173a63f9a4efeee7026a14e9a6c161d..b3ad02ea240265241e5f1bbb68a856306311da26 100644 (file)
--- a/src/tests/bigint_test.c
+++ b/src/tests/bigint_test.c
@@ -841,6 +841,7 @@ static void bigint_mod_exp_okx ( struct bigint_test *base,
  */
 static void bigint_test_exec ( void ) {
 
+       bigint_add_ok ( BIGINT(), BIGINT(), BIGINT(), 0 );
        bigint_add_ok ( BIGINT ( 0x8a ),
                        BIGINT ( 0x43 ),
                        BIGINT ( 0xcd ), 0 );
@@ -934,6 +935,7 @@ static void bigint_test_exec ( void ) {
                                 0x9f, 0x60, 0x58, 0xff, 0xb6, 0x76, 0x45,
                                 0xe6, 0xed, 0x61, 0x8d, 0xe6, 0xc0, 0x72,
                                 0x1c, 0x07 ), 0 );
+       bigint_subtract_ok ( BIGINT(), BIGINT(), BIGINT(), 0 );
        bigint_subtract_ok ( BIGINT ( 0x83 ),
                             BIGINT ( 0x50 ),
                             BIGINT ( 0xcd ), 1 );
@@ -1033,6 +1035,7 @@ static void bigint_test_exec ( void ) {
                                      0xda, 0xc8, 0x8c, 0x71, 0x86, 0x97,
                                      0x7f, 0xcb, 0x94, 0x31, 0x1d, 0xbc,
                                      0x44, 0x1a ), 0 );
+       bigint_shl_ok ( BIGINT(), BIGINT(), 0 );
        bigint_shl_ok ( BIGINT ( 0xe0 ),
                        BIGINT ( 0xc0 ), 1 );
        bigint_shl_ok ( BIGINT ( 0x43, 0x1d ),
@@ -1099,6 +1102,7 @@ static void bigint_test_exec ( void ) {
                                 0x49, 0x7c, 0x1e, 0xdb, 0xc7, 0x65, 0xa6,
                                 0x0e, 0xd1, 0xd2, 0x00, 0xb3, 0x41, 0xc9,
                                 0x3c, 0xbc ), 0 );
+       bigint_shr_ok ( BIGINT(), BIGINT(), 0 );
        bigint_shr_ok ( BIGINT ( 0x8f ),
                        BIGINT ( 0x47 ), 1 );
        bigint_shr_ok ( BIGINT ( 0xaa, 0x1d ),
@@ -1165,6 +1169,7 @@ static void bigint_test_exec ( void ) {
                                 0x46, 0xa8, 0x94, 0xb0, 0xf7, 0xa4, 0x57,
                                 0x1f, 0x72, 0x88, 0x5f, 0xed, 0x4d, 0xc9,
                                 0x59, 0xbb ), 1 );
+       bigint_is_zero_ok ( BIGINT(), 1 );
        bigint_is_zero_ok ( BIGINT ( 0x9b ),
                            0 );
        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 ),
                            0 );
+       bigint_is_geq_ok ( BIGINT(), BIGINT(), 1 );
        bigint_is_geq_ok ( BIGINT ( 0xa2 ),
                           BIGINT ( 0x58 ),
                           1 );
@@ -1540,6 +1546,7 @@ static void bigint_test_exec ( void ) {
                                        0x83, 0xf8, 0xa2, 0x11, 0xf5, 0xd4,
                                        0xcb, 0xe0 ),
                               1013, 0 );
+       bigint_max_set_bit_ok ( BIGINT(), 0 );
        bigint_max_set_bit_ok ( BIGINT ( 0x3a ),
                                6 );
        bigint_max_set_bit_ok ( BIGINT ( 0x03 ),