ClassByteCodeAnnotationFilter doesn't read the constants pool correctly
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Key: MYFACES-2930
URL: https://issues.apache.org/jira/browse/MYFACES-2930
Project: MyFaces Core
Issue Type: Bug
Components: General
Affects Versions: 2.0.3-SNAPSHOT
Reporter: Christian Kaltepoth
Priority: Minor
Attachments: MYFACES-2930.patch
The ClassByteCodeAnnotationFilter used to check classes for annotations by
reading their bytecode doesn't read the constants pool table correctly.
The current code reads the number of entries from the class file and then reads
each entry in the pool in a "for" loop. Unfortunately the code fails to process
entries of the type "CONSTANT_Long" and "CONSTANT_Double" correctly. The Java
VM spec says:
"All 8-byte constants take up two entries in the constant_pool table of the
class file. If a CONSTANT_Long_info or CONSTANT_Double_info structure is the
item in the constant_pool table at index n, then the next usable item in the
pool is located at index n+2. The constant_pool index n+1 must be valid but is
considered unusable."
From:
http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html#1348
The ClassByteCodeAnnotationFilter doesn't increase the loop counter for these
entry types. Thus the filter will read bytes outside of the constants pool as
soon as it finds a double or long constant in the constants pool because it
will try to read more entries than there actually are.
Please note that this doesn't lead to faulty behavior of the class, because if
the reader reaches the end of the constants pool, it didn't find any reference
until then and therefore it is OK to abort scanning and return "false".
Find attached a patch containing a fix for this issue and a small unit test for
the ClassByteCodeAnnotationFilter. I also added a log statement to default
block of the switch statement. I guess this wasn't done because the current
implementation often found bad tag values because of this bug.
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