lib/portage/util: fix bundled whirlpool on empty bytestring input

The WhirlpoolAdd function did not consider zero-length input, so calls
to update(b'') would produce out-of-bounds errors. This was not covered
by any tests, because the constructor implicitly skipped the call to
update on zero-length input.

Add check for zero-length input to WhirlpoolAdd, and have the Whirlpool
constructor skip calling update() only if arg is None.

Closes: https://bugs.gentoo.org/846389
Signed-off-by: Thomas Bracht Laumann Jespersen <t@laumann.xyz>
Closes: https://github.com/gentoo/portage/pull/832
Signed-off-by: Michał Górny <mgorny@gentoo.org>

1 files changed, 11 insertions, 5 deletions

diff --git a/lib/portage/util/whirlpool.py b/lib/portage/util/whirlpool.py
index de344d8eb..9178d70c7 100644
--- a/lib/portage/util/whirlpool.py
+++ b/lib/portage/util/whirlpool.py
@@ -37,11 +37,9 @@ class Whirlpool:
     may be provided; if present, this string will be automatically
     hashed."""
 
-    def __init__(self, arg=None):
+    def __init__(self, arg=b""):
         self.ctx = WhirlpoolStruct()
-        if arg:
-            self.update(arg)
-        self.digest_status = 0
+        self.update(arg)
 
     def update(self, arg):
         """update(arg)"""
@@ -71,7 +69,7 @@ class Whirlpool:
         return copy.deepcopy(self)
 
 
-def new(init=None):
+def new(init=b""):
     """Return a new Whirlpool object. An optional string argument
     may be provided; if present, this string will be automatically
     hashed."""
@@ -2183,6 +2181,8 @@ def WhirlpoolInit(ctx):
 def WhirlpoolAdd(source, sourceBits, ctx):
     if not isinstance(source, bytes):
         raise TypeError("Expected %s, got %s" % (bytes, type(source)))
+    if sourceBits == 0:
+        return
 
     carry = 0
     value = sourceBits
@@ -2350,3 +2350,9 @@ if __name__ == "__main__":
         Whirlpool(b"").hexdigest()
         == "19fa61d75522a4669b44e39c1d2e1726c530232130d407f89afee0964997f7a73e83be698b288febcf88e3e03c4f0757ea8964e59b63d93708b138cc42a66eb3"
     )
+    w = Whirlpool()
+    w.update(b"")
+    assert (
+        w.hexdigest()
+        == "19fa61d75522a4669b44e39c1d2e1726c530232130d407f89afee0964997f7a73e83be698b288febcf88e3e03c4f0757ea8964e59b63d93708b138cc42a66eb3"
+    )