Move asn1_skip_integer to the asn1_helpers module
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/src/asn1_helpers.c b/tests/src/asn1_helpers.c
index 6ffdca9..79aa166 100644
--- a/tests/src/asn1_helpers.c
+++ b/tests/src/asn1_helpers.c
@@ -23,3 +23,52 @@
#include <test/helpers.h>
#include <test/macros.h>
+#if defined(MBEDTLS_ASN1_PARSE_C)
+
+#include <mbedtls/asn1.h>
+
+int mbedtls_test_asn1_skip_integer( unsigned char **p, const unsigned char *end,
+ size_t min_bits, size_t max_bits,
+ int must_be_odd )
+{
+ size_t len;
+ size_t actual_bits;
+ unsigned char msb;
+ TEST_EQUAL( mbedtls_asn1_get_tag( p, end, &len,
+ MBEDTLS_ASN1_INTEGER ),
+ 0 );
+
+ /* Check if the retrieved length doesn't extend the actual buffer's size.
+ * It is assumed here, that end >= p, which validates casting to size_t. */
+ TEST_ASSERT( len <= (size_t)( end - *p) );
+
+ /* Tolerate a slight departure from DER encoding:
+ * - 0 may be represented by an empty string or a 1-byte string.
+ * - The sign bit may be used as a value bit. */
+ if( ( len == 1 && ( *p )[0] == 0 ) ||
+ ( len > 1 && ( *p )[0] == 0 && ( ( *p )[1] & 0x80 ) != 0 ) )
+ {
+ ++( *p );
+ --len;
+ }
+ if( min_bits == 0 && len == 0 )
+ return( 1 );
+ msb = ( *p )[0];
+ TEST_ASSERT( msb != 0 );
+ actual_bits = 8 * ( len - 1 );
+ while( msb != 0 )
+ {
+ msb >>= 1;
+ ++actual_bits;
+ }
+ TEST_ASSERT( actual_bits >= min_bits );
+ TEST_ASSERT( actual_bits <= max_bits );
+ if( must_be_odd )
+ TEST_ASSERT( ( ( *p )[len-1] & 1 ) != 0 );
+ *p += len;
+ return( 1 );
+exit:
+ return( 0 );
+}
+
+#endif /* MBEDTLS_ASN1_PARSE_C */