pkcs11: Properly handle EC_POINTs returned as ASN.1 octet string

This is the correct encoding but we internally only use unwrapped keys
and some tokens return them unwrapped.

Fixes #872.

diff --git a/src/libstrongswan/plugins/pkcs11/pkcs11_library.c b/src/libstrongswan/plugins/pkcs11/pkcs11_library.c
index 7661473b14ac11cc3b916833a2ff3cbdae450e67..dc8a1f17ab3c20cc9466276c9ed792cb7124a90d 100644 (file)
--- a/src/libstrongswan/plugins/pkcs11/pkcs11_library.c
+++ b/src/libstrongswan/plugins/pkcs11/pkcs11_library.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011 Tobias Brunner
+ * Copyright (C) 2011-2015 Tobias Brunner
  * Hochschule fuer Technik Rapperswil
  *
  * Copyright (C) 2010 Martin Willi
@@ -21,6 +21,7 @@
 #include <dlfcn.h>
 
 #include <library.h>
+#include <asn1/asn1.h>
 #include <utils/debug.h>
 #include <threading/mutex.h>
 #include <collections/linked_list.h>
@@ -640,11 +641,38 @@ static void free_attrs(object_enumerator_t *this)
        }
 }
 
+/**
+ * CKA_EC_POINT is encodeed as ASN.1 octet string, we can't handle that and
+ * some tokens actually return them even unwrapped.
+ *
+ * Because ASN1_OCTET_STRING is 0x04 and uncompressed EC_POINTs also begin with
+ * 0x04 (compressed ones with 0x02 or 0x03) there will be an attempt to parse
+ * unwrapped uncompressed EC_POINTs.  This will fail in most cases as the length
+ * will not be correct, however, there is a small chance that the key's first
+ * byte denotes the correct length.  Checking the first byte of the key should
+ * further reduce the risk of false positives, though.
+ *
+ * The original memory is freed if the value is unwrapped.
+ */
+static void unwrap_ec_point(chunk_t *data)
+{
+       chunk_t wrapped, unwrapped;
+
+       wrapped = unwrapped = *data;
+       if (asn1_unwrap(&unwrapped, &unwrapped) == ASN1_OCTET_STRING &&
+               unwrapped.len && unwrapped.ptr[0] >= 0x02 && unwrapped.ptr[0] <= 0x04)
+       {
+               *data = chunk_clone(unwrapped);
+               free(wrapped.ptr);
+       }
+}
+
 /**
  * Get attributes for a given object during enumeration
  */
 static bool get_attributes(object_enumerator_t *this, CK_OBJECT_HANDLE object)
 {
+       chunk_t data;
        CK_RV rv;
        int i;
 
@@ -677,6 +705,16 @@ static bool get_attributes(object_enumerator_t *this, CK_OBJECT_HANDLE object)
                DBG1(DBG_CFG, "C_GetAttributeValue() error: %N", ck_rv_names, rv);
                return FALSE;
        }
+       for (i = 0; i < this->count; i++)
+       {
+               if (this->attr[i].type == CKA_EC_POINT)
+               {
+                       data = chunk_create(this->attr[i].pValue, this->attr[i].ulValueLen);
+                       unwrap_ec_point(&data);
+                       this->attr[i].pValue = data.ptr;
+                       this->attr[i].ulValueLen = data.len;
+               }
+       }
        return TRUE;
 }
 
@@ -887,6 +925,10 @@ METHOD(pkcs11_library_t, get_ck_attribute, bool,
                chunk_free(data);
                return FALSE;
        }
+       if (attr.type == CKA_EC_POINT)
+       {
+               unwrap_ec_point(data);
+       }
        return TRUE;
 }