Challenge

Analysing the Honeynet Project challenge PDF file with peepdf (II)

After the "useless" analysis of the fake objects now we can focus on the objects which will be parsed by the PDF reader:

/Catalog (27)
dictionary (28)
dictionary (22)
dictionary (23)
dictionary (22)
/Annot (24)
dictionary (23)
/Page (25)
/Pages (26)
/Page (25)
stream (21)
/Pages (26)

If we take a look at the Catalog object...

PPDF> object 27

<< /AcroForm 28 0 R
/MarkInfo << /Marked true >>
/Pages 26 0 R
/Type /Catalog
/Lang en-us
/PageMode /UseAttachments >>

There is no presence of any triggers here (/OpenAction) or in the rest of the objects (/AA) so it seems that the /AcroForm element has something to say. Also, the suspicious object 21 (/EmbeddedFile) is related with this interactive form:

PPDF> references to 21

[28]

PPDF> object 28

<< /DA /Helv 0 Tf 0 g
/Fields [ 22 0 R ]
/XFA [ template 21 0 R ] >>

In the dictionary of the form we can see that object 21 is a template and that there is a reference to a field object (object 22). So we continue analysing the field objects:

PPDF> object 22

<< /V

Analysing the Honeynet Project challenge PDF file with peepdf (I)

In past November The Honeynet Project published a new challenge, this time related to PDF files. Although it's quite old I'm going to analyse it with my tool because I think it has some interesting tricks and peepdf makes the analysis easier. The PDF file can be downloaded from here.

If we launch peepdf we obtain this error:

$ ./peepdf.py -i fcexploit.pdf

Error: parsing indirect object!!

It seems that there is an error in the parsing process. Talking about malicious PDF files it's recommended to add the -f option to ignore this type of errors and continue with the analysis:

$ ./peepdf.py -fi fcexploit.pdf

File: fcexploit.pdf
MD5: 659cf4c6baa87b082227540047538c2a
Size: 25169 bytes
Version: 1.3
Binary: True
Linearized: False
Encrypted: False
Updates: 0
Objects: 18
Streams: 5
Comments: 0
Errors: 2

Version 0:
Catalog: 27
Info: 11
Objects (18): [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 22, 23, 24, 25, 26, 27, 28]
Errors (1): [11]
Streams (5): [5, 7, 9, 10, 11]
Encoded (4): [5, 7, 9, 10]
Objects with JS code (1): [5]
Suspicious elements:
/AcroForm: [27]
/OpenAction: [1]
/JS: [4]
/JavaScript: [4]
getAnnots (CVE-2009-1492): [5]

Now we can see some statistics and information about the document. We can see some errors too, proof that it's not a normal PDF file:

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