Class: Memorandom::Plugins::CAPI

Inherits:
Memorandom::PluginTemplate show all
Defined in:
lib/memorandom/plugins/capi.rb

Constant Summary collapse

@@description = 
"This plugin looks for Microsoft CryptoAPI encryption keys in memory (PRIVATEBLOB)"
@@confidence = 
0.90

Instance Attribute Summary

Attributes inherited from Memorandom::PluginTemplate

#hits, #scanner

Instance Method Summary collapse

Methods inherited from Memorandom::PluginTemplate

#confidence, confidence, #description, description, #initialize, #report_hit, #reset

Constructor Details

This class inherits a constructor from Memorandom::PluginTemplate

Instance Method Details

#scan(buffer, source_offset) ⇒ Object

Scan takes a buffer and an offset of where this buffer starts in the source



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# File 'lib/memorandom/plugins/capi.rb', line 11

def scan(buffer, source_offset)

  buffer.scan(
    /[\x06\x07]\x02.{6}(?:RSA1|RSA2|DSS1|DSS2).{20}/
  ).each do |m|
    # This may hit an earlier identical match, but thats ok
    last_offset = buffer.index(m)
    next unless last_offset 

    # Attempt to parse the key at the specified offset
    key_candidate = buffer[last_offset, 20000]
    key_type = ""
    key      = nil

    bits = key_candidate.unpack("CCA6A4V")
    key_type << ( bits[3] + "-" + bits[4].to_s + "-" )
    key_type << ( (bits[0] == 0x07) ? "Private" : "Public" )

    key_length = 0
    nbyte  = (bits[4] +  7) >> 3
    hnbyte = (bits[4] + 15) >> 4 

    # DSA
    if bits[3].index('DSS')
      if bits[0] == 0x06
        # Expected length: 20 for q + 3 components bitlen each + 24 for seed structure.
        key_length = 44 + (3 * nbyte)
      else
        # Expected length: 20 for q, priv, 2 bitlen components + 24 for seed structure.
        key_length = 64 + (2 * nbyte)
      end
    # RSA
    else
      if bits[0] == 0x06
        # Expected length: 4 for 'e' + 'n'
        key_length = 4 + nbyte
      else
        # Expected length: 4 for 'e' and 7 other components. 2 components are bitlen size, 5 are bitlen/2
        key_length = 4 + (2 * nbyte) + (5 * hnbyte)
      end
    end

    key = buffer[last_offset, key_length + 16]
    next unless key.length == (key_length+16)

    report_hit(:type => "CAPI-#{key_type}", :data => key, :offset => source_offset + last_offset)
  end
end