[Bug 1872560] Re: integer overflow in whoopsie 0.2.69

[Sebastien Bacher]

** Changed in: whoopsie (Ubuntu)
       Status: New => Confirmed

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Title:
  integer overflow in whoopsie 0.2.69

Status in whoopsie package in Ubuntu:
  Confirmed

Bug description:
  Hi,

  I have found a security issue on whoopsie 0.2.69 and earlier.

  ## Vulnerability in whoopsie
  - whoopsie 0.2.69 and earlier have a heap-based buffer overflow vulnerability. 
  - An attacker can cause a denial of service (memory corruption and application crash) via a crafted .crash file.

  
  ## Basic
  When a program has been crashed, Linux system tries to create a '.crash' file on '/var/crash/' directory with python script located in '/usr/share/apport/apport'. 
  The file contains a series of system crash information including core dump, syslog, stack trace, memory map info, etc.
  After the creation of '.crash' file, whoopsie extracts the above information from the '.crash' file and encodes it into binary json (bson) format.
  Lastly, whoopsie forwards the data to a remotely connected Ubuntu Error Report system.

   
  ## Vulnerability
  Unfortunately, we have found a heap-based buffer overflow vulnerability during the encoding, when whoopsie attempts to bsonify with crafted crash file.
  The data in '.crash' file is stored in key-value form and the whoopsie separately measures the length of 'key' and 'value' to allocate memory region during the encoding. 
  A heap-based buffer overflow can occur when an integer overflow happens on a variable that contains length of 'key'. 
  FYI, a issue to that raised by 'value' is well covered by performing exception handling.

  @[bson.c:663][https://git.launchpad.net/ubuntu/+source/whoopsie/tree/lib/bson/bson.c?h=applied/0.2.69#n663]

  const uint32_t len = strlen( name ) + 1;

  - Integer overflow occurs when length of ‘name’ exceeds INT32_MAX value. 
  - Here, ‘name’ indicates the ‘key’ data in ‘.crash’ file.                

  @[bson.c:627][https://git.launchpad.net/ubuntu/+source/whoopsie/tree/lib/bson/bson.c?h=applied/0.2.69#n627]

  b->data = bson_realloc( b->data, new_size );

  - Unexpected small memory region is allocated due to above integer
  overflow.

  @[bson.c:680][https://git.launchpad.net/ubuntu/+source/whoopsie/tree/lib/bson/bson.c?h=applied/0.2.69#n680]

  bson_append( b, name, len );

  - Memory corruption happens when unexpected small memory region is
  allocated.

  
  ## Attack Scenario
  1) Create a fake.crash file
  - '.crash' file is composed of the following format: 'key : value'.
  - To cause the overflow attack, the size of 'key' should be in double amount of INT32_MAX.
  - The size of 'value' doesn’t matter, but not zero length.

  $ python -c "print('A' * 0xFFFFFFFF + ' : ' + 'B')" > /var/crash/fake.crash
  $ cat fake.crash
  AAA … AA : B

  
  2) Trigger the whoopsie to read the fake.crash file
  - Just create 'fake.upload' file by touch command.
  - Or launch apport-gtk gui or apport-bug cli application.

  3) Check out the result
  - After a while, the whoopsie has been killed by segmentation fault.

  Sincerely,

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