commit b40dc58a831284dce9f85104409c73f4574d6d0d
author Hanno Becker <hanno.becker@arm.com> Wed Feb 20 09:38:45 2019 +0000
committer Hanno Becker <hanno.becker@arm.com> Tue Jun 25 09:00:25 2019 +0100
tree 6a5fe3db62e1a8d6224d79a0c54b3b72675348ff
parent ace04a6dc3dd079935163ce4d566ef960fd3d1d9

Introduce a helper macro to check for ASN.1 string tags

This commit introduces a macro `MBEDTLS_ASN1_IS_STRING_TAG`
that can be used to check if an ASN.1 tag is among the list
of string tags:
- MBEDTLS_ASN1_BMP_STRING
- MBEDTLS_ASN1_UTF8_STRING
- MBEDTLS_ASN1_T61_STRING
- MBEDTLS_ASN1_IA5_STRING
- MBEDTLS_ASN1_UNIVERSAL_STRING
- MBEDTLS_ASN1_PRINTABLE_STRING
- MBEDTLS_ASN1_BIT_STRING

include/mbedtls/asn1.h

diff --git a/include/mbedtls/asn1.h b/include/mbedtls/asn1.h
index 96c1c9a..2fb6de0 100644
--- a/include/mbedtls/asn1.h
+++ b/include/mbedtls/asn1.h
@@ -89,6 +89,18 @@
 #define MBEDTLS_ASN1_CONSTRUCTED             0x20
 #define MBEDTLS_ASN1_CONTEXT_SPECIFIC        0x80
 
+/* Slightly smaller way to check if tag is a string tag
+ * compared to canonical implementation. */
+#define MBEDTLS_ASN1_IS_STRING_TAG( tag )                                     \
+    ( ( tag ) < 32u && (                                                      \
+        ( ( 1u << ( tag ) ) & ( ( 1u << MBEDTLS_ASN1_BMP_STRING )       |     \
+                                ( 1u << MBEDTLS_ASN1_UTF8_STRING )      |     \
+                                ( 1u << MBEDTLS_ASN1_T61_STRING )       |     \
+                                ( 1u << MBEDTLS_ASN1_IA5_STRING )       |     \
+                                ( 1u << MBEDTLS_ASN1_UNIVERSAL_STRING ) |     \
+                                ( 1u << MBEDTLS_ASN1_PRINTABLE_STRING ) |     \
+                                ( 1u << MBEDTLS_ASN1_BIT_STRING ) ) ) != 0 ) )
+
 /*
  * Bit masks for each of the components of an ASN.1 tag as specified in
  * ITU X.690 (08/2015), section 8.1 "General rules for encoding",