1 files changed, 42 insertions, 0 deletions
diff --git a/botan/src/pubkey/pubkey_enums.cpp b/botan/src/pubkey/pubkey_enums.cpp
new file mode 100644
index 0000000..327107d
--- /dev/null
+++ b/botan/src/pubkey/pubkey_enums.cpp
@@ -0,0 +1,42 @@
+/*
+* KeyUsage
+* (C) 1999-2007 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/pubkey_enums.h>
+#include <botan/ber_dec.h>
+
+namespace Botan {
+
+namespace BER {
+
+/*
+* Decode a BER encoded KeyUsage
+*/
+void decode(BER_Decoder& source, Key_Constraints& key_usage)
+   {
+   BER_Object obj = source.get_next_object();
+
+   if(obj.type_tag != BIT_STRING || obj.class_tag != UNIVERSAL)
+      throw BER_Bad_Tag("Bad tag for usage constraint",
+                        obj.type_tag, obj.class_tag);
+   if(obj.value.size() != 2 && obj.value.size() != 3)
+      throw BER_Decoding_Error("Bad size for BITSTRING in usage constraint");
+   if(obj.value[0] >= 8)
+      throw BER_Decoding_Error("Invalid unused bits in usage constraint");
+
+   const byte mask = (0xFF << obj.value[0]);
+   obj.value[obj.value.size()-1] &= mask;
+
+   u16bit usage = 0;
+   for(u32bit j = 1; j != obj.value.size(); ++j)
+      usage = (obj.value[j] << 8) | usage;
+
+   key_usage = Key_Constraints(usage);
+   }
+
+}
+
+}