diff --git a/weboob/tools/capabilities/__init__.py b/weboob/tools/capabilities/__init__.py
new file mode 100644
index 00000000..8b137891
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+++ b/weboob/tools/capabilities/__init__.py
@@ -0,0 +1 @@
+
diff --git a/weboob/tools/capabilities/paste.py b/weboob/tools/capabilities/paste.py
new file mode 100644
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+++ b/weboob/tools/capabilities/paste.py
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+# -*- coding: utf-8 -*-
+
+# Copyright(C) 2011 Laurent Bachelier
+#
+# This file is part of weboob.
+#
+# weboob is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# weboob is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with weboob. If not, see <http://www.gnu.org/licenses/>.
+
+
+from __future__ import with_statement
+
+from weboob.capabilities.paste import ICapPaste
+
+
+class BasePasteBackend(ICapPaste):
+    EXPIRATIONS = {}
+    """
+    List of expirations and their corresponding remote codes (any type can be used).
+    The expirations, i.e. the keys, are integers representing the duration
+    in seconds. There also can be one False key, for the "forever" expiration.
+    """
+
+    def get_closest_expiration(self, max_age):
+        """
+        Get the expiration closest (and less or equal to) max_age (int, in seconds).
+        max_age set to False means we want it to never expire.
+
+        @return int or False if found, else None
+        """
+        # "forever"
+        if max_age is False and False in self.EXPIRATIONS:
+            return max_age
+        # get timed expirations, longest first
+        expirations = sorted([e for e in self.EXPIRATIONS if e is not False], reverse=True)
+        # find the first expiration that is below or equal to the maximum wanted age
+        for e in expirations:
+            if max_age is False or max_age >= e:
+                return e
+
+def test():
+    class MockPasteBackend(BasePasteBackend):
+        def __init__(self, expirations):
+            self.EXPIRATIONS = expirations
+
+    # all expirations are too high
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1) is None
+    # we found a suitable lower or equal expiration
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(84) is 42
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(False) is False
+    assert MockPasteBackend({1337: '', 42: ''}).get_closest_expiration(False) is 1337
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1336) is 42
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1337) is 1337
+    assert MockPasteBackend({1337: '', 42: '', False: ''}).get_closest_expiration(1338) is 1337
+    # this format should work, though of doubtful usage
+    assert MockPasteBackend([1337, 42, False]).get_closest_expiration(84) is 42