Fix long-standing bug in error code description

MBEDTLS_ERR_ASN1_INVALID_DATA is documented as "not used", but it has
been used since the PolarSSL days.

Author: gilles-peskine-arm

include/mbedtls/asn1.h

@@ -52,7 +52,7 @@
 #define MBEDTLS_ERR_ASN1_UNEXPECTED_TAG                   -0x0062  /**< ASN1 tag was of an unexpected value. */
 #define MBEDTLS_ERR_ASN1_INVALID_LENGTH                   -0x0064  /**< Error when trying to determine the length or invalid length. */
 #define MBEDTLS_ERR_ASN1_LENGTH_MISMATCH                  -0x0066  /**< Actual length differs from expected length. */
-#define MBEDTLS_ERR_ASN1_INVALID_DATA                     -0x0068  /**< Data is invalid. (not used) */
+#define MBEDTLS_ERR_ASN1_INVALID_DATA                     -0x0068  /**< Data is invalid. */
 #define MBEDTLS_ERR_ASN1_ALLOC_FAILED                     -0x006A  /**< Memory allocation failed */
 #define MBEDTLS_ERR_ASN1_BUF_TOO_SMALL                    -0x006C  /**< Buffer too small when writing ASN.1 data structure. */
 

library/error.c

@@ -467,7 +467,7 @@ void mbedtls_strerror( int ret, char *buf, size_t buflen )
     if( use_ret == -(MBEDTLS_ERR_ASN1_LENGTH_MISMATCH) )
         mbedtls_snprintf( buf, buflen, "ASN1 - Actual length differs from expected length" );
     if( use_ret == -(MBEDTLS_ERR_ASN1_INVALID_DATA) )
-        mbedtls_snprintf( buf, buflen, "ASN1 - Data is invalid. (not used)" );
+        mbedtls_snprintf( buf, buflen, "ASN1 - Data is invalid" );
     if( use_ret == -(MBEDTLS_ERR_ASN1_ALLOC_FAILED) )
         mbedtls_snprintf( buf, buflen, "ASN1 - Memory allocation failed" );
     if( use_ret == -(MBEDTLS_ERR_ASN1_BUF_TOO_SMALL) )