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parse the 'hash' field after 'key' in IDX:branch block #97

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parse the 'hash' field after 'key' in IDX:branch block #97

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9 changes: 7 additions & 2 deletions ubireader/ubifs/nodes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -160,7 +160,9 @@ def __init__(self, buf):
setattr(self, key, fields[key])

idxs = UBIFS_IDX_NODE_SZ
brs = UBIFS_BRANCH_SZ
# Dynamic detection of `brs` (branch size), whether a hash is present after
# the key in authenticated UBIFS. Not checking the len of the hash.
brs = int((len(buf) - UBIFS_IDX_NODE_SZ) / self.child_cnt)
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The int casting is hiding low-level details. Do you want to round up or round down ? It would be cleaner with math.floor or math.ceil, depending on implementation details. You can also use // instead of / if you want to round down.

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I think // is what I was trying to achieve. In theory, if the UBIFS image is correctly formatted, the division by self.child_cnt has no remainder. My int( ... ) was a clumsy attempt to get rid of the .0 in the result of the division. (Because brs needs to be an int, not a float.)

I'll use // instead. I'll also rewrite the comment, because I'm having a hard time to understand myself after a few months.

setattr(self, 'branches', [branch(buf[idxs+(brs*i):idxs+(brs*i)+brs]) for i in range(0, self.child_cnt)])
setattr(self, 'errors', [])

Expand All @@ -183,13 +185,16 @@ class branch(object):
Bin:buf -- Raw data to extract header information from.
"""
def __init__(self, buf):
fields = dict(list(zip(UBIFS_BRANCH_FIELDS, struct.unpack(UBIFS_BRANCH_FORMAT, buf))))
fields = dict(list(zip(UBIFS_BRANCH_FIELDS, struct.unpack(UBIFS_BRANCH_FORMAT, buf[0:UBIFS_BRANCH_SZ]))))
for key in fields:
if key == 'key':
setattr(self, key, parse_key(fields[key]))
else:
setattr(self, key, fields[key])

if len(buf) > (UBIFS_BRANCH_SZ):
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Why is UBIFS_BRANCH_SZ between parentheses ?

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For no reason. I forgot to remove them. (Maybe in a previous iteration, this was (UBIFS_BRANCH_SZ + something) ?

I'll remove those unneeded parentheses.

setattr(self, 'hash', buf[UBIFS_BRANCH_SZ:])

setattr(self, 'errors', [])

def __repr__(self):
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