prohibit indefinite length DER encoding

1 files changed, 3 insertions, 0 deletions

diff --git a/pyasn1/codec/der/encoder.py b/pyasn1/codec/der/encoder.py
index 2044df3..7f55eeb 100644
--- a/pyasn1/codec/der/encoder.py
+++ b/pyasn1/codec/der/encoder.py
@@ -1,6 +1,7 @@
 # DER encoder
 from pyasn1.type import univ
 from pyasn1.codec.cer import encoder
+from pyasn1 import error
 
 class SetOfEncoder(encoder.SetOfEncoder):
     def _cmpSetComponents(self, c1, c2):
@@ -24,6 +25,8 @@ typeMap = encoder.typeMap
 class Encoder(encoder.Encoder):
     supportIndefLength = False
     def __call__(self, client, defMode=True, maxChunkSize=0):
+        if not defMode:
+            raise error.PyAsn1Error('DER forbids indefinite length mode')
         return encoder.Encoder.__call__(self, client, defMode, maxChunkSize)
 
 encode = Encoder(tagMap, typeMap)