Merge pull request #297 from gilles-peskine-arm/asn1_get_int-undefined_shift
Fix int overflow in mbedtls_asn1_get_int
diff --git a/library/asn1parse.c b/library/asn1parse.c
index 4764ca4..412259e 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -149,16 +149,26 @@
if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_INTEGER ) ) != 0 )
return( ret );
- if( len == 0 || ( **p & 0x80 ) != 0 )
+ /* len==0 is malformed (0 must be represented as 020100). */
+ if( len == 0 )
+ return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+ /* This is a cryptography library. Reject negative integers. */
+ if( ( **p & 0x80 ) != 0 )
return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+ /* Skip leading zeros. */
while( len > 0 && **p == 0 )
{
++( *p );
--len;
}
+
+ /* Reject integers that don't fit in an int. This code assumes that
+ * the int type has no padding bit. */
if( len > sizeof( int ) )
return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+ if( len == sizeof( int ) && ( **p & 0x80 ) != 0 )
+ return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
*val = 0;
while( len-- > 0 )
diff --git a/tests/suites/test_suite_asn1parse.data b/tests/suites/test_suite_asn1parse.data
index c5d9136..4abae0b 100644
--- a/tests/suites/test_suite_asn1parse.data
+++ b/tests/suites/test_suite_asn1parse.data
@@ -164,8 +164,7 @@
get_boolean:"020101":0:MBEDTLS_ERR_ASN1_UNEXPECTED_TAG
Empty INTEGER
-depends_on:SUPPORT_NEGATIVE_INTEGERS
-get_integer:"0200":"":MBEDTLS_ERR_ASN1_INVALID_LENGTH
+empty_integer:"0200"
INTEGER 0
get_integer:"020100":"0":0
@@ -173,27 +172,15 @@
INTEGER 0, extra leading 0
get_integer:"02020000":"0":0
-INTEGER -0
-depends_on:SUPPORT_NEGATIVE_INTEGERS
-get_integer:"020180":"0":0
-
INTEGER 1
get_integer:"020101":"1":0:
INTEGER 1, extra leading 0
get_integer:"02020001":"1":0:
-INTEGER -1
-depends_on:SUPPORT_NEGATIVE_INTEGERS
-get_integer:"020181":"-1":0
-
INTEGER 0x7f
get_integer:"02017f":"7f":0
-INTEGER -0x7f
-depends_on:SUPPORT_NEGATIVE_INTEGERS
-get_integer:"0201ff":"-7f":0
-
INTEGER 0x80
get_integer:"02020080":"80":0
@@ -212,9 +199,30 @@
INTEGER 0x12345678, extra leading 0
get_integer:"02050012345678":"12345678":0
+INTEGER 0x7fffffff
+get_integer:"02047fffffff":"7fffffff":0
+
+INTEGER 0x7fffffff, extra leading 0
+get_integer:"0205007fffffff":"7fffffff":0
+
+INTEGER 0x80000000
+get_integer:"02050080000000":"80000000":0
+
+INTEGER 0xffffffff
+get_integer:"020500ffffffff":"ffffffff":0
+
+INTEGER 0x100000000
+get_integer:"02050100000000":"0100000000":0
+
INTEGER 0x123456789abcdef0
get_integer:"0208123456789abcdef0":"123456789abcdef0":0
+INTEGER 0xfedcab9876543210
+get_integer:"020900fedcab9876543210":"fedcab9876543210":0
+
+INTEGER 0x1fedcab9876543210
+get_integer:"020901fedcab9876543210":"1fedcab9876543210":0
+
INTEGER with 127 value octets
get_integer:"027f0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcd":"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcd":0
@@ -227,6 +235,51 @@
INTEGER with 128 value octets (leading 0 in length)
get_integer:"028200800123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef":"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef":0
+INTEGER -1
+get_integer:"0201ff":"-1":0
+
+INTEGER -1, extra leading ff
+get_integer:"0202ffff":"-1":0
+
+INTEGER -0x7f
+get_integer:"020181":"-7f":0
+
+INTEGER -0x80
+get_integer:"020180":"-80":0
+
+INTEGER -0x81
+get_integer:"0202ff7f":"-81":0
+
+INTEGER -0xff
+get_integer:"0202ff01":"-ff":0
+
+INTEGER -0x100
+get_integer:"0202ff00":"-100":0
+
+INTEGER -0x7fffffff
+get_integer:"020480000001":"-7fffffff":0
+
+INTEGER -0x80000000
+get_integer:"020480000000":"-80000000":0
+
+INTEGER -0x80000001
+get_integer:"0205ff7fffffff":"-80000001":0
+
+INTEGER -0xffffffff
+get_integer:"0205ff00000001":"-ffffffff":0
+
+INTEGER -0x100000000
+get_integer:"0205ff00000000":"-100000000":0
+
+INTEGER -0x123456789abcdef0
+get_integer:"0208edcba98765432110":"-123456789abcdef0":0
+
+INTEGER -0xfedcba9876543210
+get_integer:"0209ff0123456789abcdf0":"-fedcba9876543210":0
+
+INTEGER -0x1fedcab9876543210
+get_integer:"0209fe0123546789abcdf0":"-1fedcab9876543210":0
+
Not INTEGER
get_integer:"010101":"":MBEDTLS_ERR_ASN1_UNEXPECTED_TAG
diff --git a/tests/suites/test_suite_asn1parse.function b/tests/suites/test_suite_asn1parse.function
index 3bfb1c7..defbd01 100644
--- a/tests/suites/test_suite_asn1parse.function
+++ b/tests/suites/test_suite_asn1parse.function
@@ -59,6 +59,10 @@
*p = start;
ret = mbedtls_asn1_get_mpi( p, end, &mpi );
mbedtls_mpi_free( &mpi );
+#else
+ *p = start + 1;
+ ret = mbedtls_asn1_get_len( p, end, &len );
+ *p += len;
#endif
/* If we're sure that the number fits in an int, also
* call mbedtls_asn1_get_int(). */
@@ -247,6 +251,41 @@
/* END_CASE */
/* BEGIN_CASE */
+void empty_integer( const data_t *input )
+{
+ unsigned char *p;
+#if defined(MBEDTLS_BIGNUM_C)
+ mbedtls_mpi actual_mpi;
+#endif
+ int val;
+
+#if defined(MBEDTLS_BIGNUM_C)
+ mbedtls_mpi_init( & actual_mpi );
+#endif
+
+ /* An INTEGER with no content is not valid. */
+ p = input->x;
+ TEST_EQUAL( mbedtls_asn1_get_int( &p, input->x + input->len, &val ),
+ MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+
+#if defined(MBEDTLS_BIGNUM_C)
+ /* INTEGERs are sometimes abused as bitstrings, so the library accepts
+ * an INTEGER with empty content and gives it the value 0. */
+ p = input->x;
+ TEST_EQUAL( mbedtls_asn1_get_mpi( &p, input->x + input->len, &actual_mpi ),
+ 0 );
+ TEST_EQUAL( mbedtls_mpi_cmp_int( &actual_mpi, 0 ), 0 );
+#endif
+
+exit:
+#if defined(MBEDTLS_BIGNUM_C)
+ mbedtls_mpi_free( &actual_mpi );
+#endif
+ /*empty cleanup in some configurations*/ ;
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
void get_integer( const data_t *input,
const char *expected_hex, int expected_result )
{
@@ -254,16 +293,18 @@
#if defined(MBEDTLS_BIGNUM_C)
mbedtls_mpi expected_mpi;
mbedtls_mpi actual_mpi;
+ mbedtls_mpi complement;
+ int expected_result_for_mpi = expected_result;
#endif
long expected_value;
int expected_result_for_int = expected_result;
- int expected_result_for_mpi = expected_result;
int val;
int ret;
#if defined(MBEDTLS_BIGNUM_C)
mbedtls_mpi_init( &expected_mpi );
mbedtls_mpi_init( &actual_mpi );
+ mbedtls_mpi_init( &complement );
#endif
errno = 0;
@@ -275,6 +316,16 @@
#endif
) )
{
+ /* The library returns the dubious error code INVALID_LENGTH
+ * for integers that are out of range. */
+ expected_result_for_int = MBEDTLS_ERR_ASN1_INVALID_LENGTH;
+ }
+ if( expected_result == 0 && expected_value < 0 )
+ {
+ /* The library does not support negative INTEGERs and
+ * returns the dubious error code INVALID_LENGTH.
+ * Test that we preserve the historical behavior. If we
+ * decide to change the behavior, we'll also change this test. */
expected_result_for_int = MBEDTLS_ERR_ASN1_INVALID_LENGTH;
}
@@ -300,7 +351,34 @@
TEST_EQUAL( ret, expected_result_for_mpi );
if( ret == 0 )
{
- TEST_ASSERT( mbedtls_mpi_cmp_mpi( &actual_mpi , &expected_mpi ) == 0 );
+ if( expected_value >= 0 )
+ {
+ TEST_ASSERT( mbedtls_mpi_cmp_mpi( &actual_mpi,
+ &expected_mpi ) == 0 );
+ }
+ else
+ {
+ /* The library ignores the sign bit in ASN.1 INTEGERs
+ * (which makes sense insofar as INTEGERs are sometimes
+ * abused as bit strings), so the result of parsing them
+ * is a positive integer such that expected_mpi +
+ * actual_mpi = 2^n where n is the length of the content
+ * of the INTEGER. (Leading ff octets don't matter for the
+ * expected value, but they matter for the actual value.)
+ * Test that we don't change from this behavior. If we
+ * decide to fix the library to change the behavior on
+ * negative INTEGERs, we'll fix this test code. */
+ unsigned char *q = input->x + 1;
+ size_t len;
+ TEST_ASSERT( mbedtls_asn1_get_len( &q, input->x + input->len,
+ &len ) == 0 );
+ TEST_ASSERT( mbedtls_mpi_lset( &complement, 1 ) == 0 );
+ TEST_ASSERT( mbedtls_mpi_shift_l( &complement, len * 8 ) == 0 );
+ TEST_ASSERT( mbedtls_mpi_add_mpi( &complement, &complement,
+ &expected_mpi ) == 0 );
+ TEST_ASSERT( mbedtls_mpi_cmp_mpi( &complement,
+ &actual_mpi ) == 0 );
+ }
TEST_ASSERT( p == input->x + input->len );
}
#endif
@@ -309,7 +387,9 @@
#if defined(MBEDTLS_BIGNUM_C)
mbedtls_mpi_free( &expected_mpi );
mbedtls_mpi_free( &actual_mpi );
+ mbedtls_mpi_free( &complement );
#endif
+ /*empty cleanup in some configurations*/ ;
}
/* END_CASE */
