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"""Defines helpful decoders that can be used to decode information from the
flows.
A decoder is generally a callable that accepts a string and returns the value
object.
"""
import netaddr
class Decoder(object):
"""Base class for all decoder classes."""
def to_json(self):
raise NotImplementedError()
def decode_default(value):
"""Default decoder.
It tries to convert into an integer value and, if it fails, just
returns the string.
"""
try:
return int(value, 0)
except ValueError:
return value
def decode_flag(value):
"""Decode a flag. It's existence is just flagged by returning True."""
return True
def decode_int(value):
"""Integer decoder.
Both base10 and base16 integers are supported.
Used for fields such as:
n_bytes=34
metadata=0x4
"""
return int(value, 0)
def decode_time(value):
"""Time decoder.
Used for fields such as:
duration=1234.123s
"""
if value == "never":
return value
time_str = value.rstrip("s")
return float(time_str)
class IntMask(Decoder):
"""Base class for Integer Mask decoder classes.
It supports decoding a value/mask pair. The class has to be derived,
and the size attribute must be set.
"""
size = None # Size in bits.
def __init__(self, string):
if not self.size:
raise NotImplementedError(
"IntMask should be derived and size should be fixed"
)
parts = string.split("/")
if len(parts) > 1:
self._value = int(parts[0], 0)
self._mask = int(parts[1], 0)
if self._mask.bit_length() > self.size:
raise ValueError(
"Integer mask {} is bigger than size {}".format(
self._mask, self.size
)
)
else:
self._value = int(parts[0], 0)
self._mask = self.max_mask()
if self._value.bit_length() > self.size:
raise ValueError(
"Integer value {} is bigger than size {}".format(
self._value, self.size
)
)
@property
def value(self):
return self._value
@property
def mask(self):
return self._mask
def max_mask(self):
return 2 ** self.size - 1
def fully(self):
"""Returns True if it's fully masked."""
return self._mask == self.max_mask()
def __str__(self):
if self.fully():
return str(self._value)
else:
return "{}/{}".format(hex(self._value), hex(self._mask))
def __repr__(self):
return "%s('%s')" % (self.__class__.__name__, self)
def __eq__(self, other):
"""Equality operator.
Both value and mask must be the same for the comparison to result True.
This can be used to implement filters that expect a specific mask,
e.g: ct.state = 0x1/0xff.
Args:
other (IntMask): Another IntMask to compare against.
Returns:
True if the other IntMask is the same as this one.
"""
if isinstance(other, IntMask):
return self.value == other.value and self.mask == other.mask
elif isinstance(other, int):
return self.value == other and self.mask == self.max_mask()
else:
raise ValueError("Cannot compare against ", other)
def __contains__(self, other):
"""Contains operator.
Args:
other (int or IntMask): Another integer or fully-masked IntMask
to compare against.
Returns:
True if the other integer or fully-masked IntMask is
contained in this IntMask.
Example:
0x1 in IntMask("0xf1/0xff"): True
0x1 in IntMask("0xf1/0x0f"): True
0x1 in IntMask("0xf1/0xf0"): False
"""
if isinstance(other, IntMask):
if other.fully():
return other.value in self
else:
raise ValueError(
"Comparing non fully-masked IntMasks is not supported"
)
else:
return other & self._mask == self._value & self._mask
def dict(self):
return {"value": self._value, "mask": self._mask}
def to_json(self):
return self.dict()
class Mask8(IntMask):
size = 8
class Mask16(IntMask):
size = 16
class Mask32(IntMask):
size = 32
class Mask64(IntMask):
size = 64
class Mask128(IntMask):
size = 128
class Mask992(IntMask):
size = 992
def decode_mask(mask_size):
"""Value/Mask decoder for values of specific size (bits).
Used for fields such as:
reg0=0x248/0xff
"""
class Mask(IntMask):
size = mask_size
__name__ = "Mask{}".format(size)
return Mask
class EthMask(Decoder):
"""EthMask represents an Ethernet address with optional mask.
It uses netaddr.EUI.
Attributes:
eth (netaddr.EUI): The Ethernet address.
mask (netaddr.EUI): Optional, the Ethernet address mask.
Args:
string (str): A string representing the masked Ethernet address
e.g: 00.11:22:33:44:55 or 01:00:22:00:33:00/01:00:00:00:00:00
"""
def __init__(self, string):
mask_parts = string.split("/")
self._eth = netaddr.EUI(mask_parts[0])
if len(mask_parts) == 2:
self._mask = netaddr.EUI(mask_parts[1])
else:
self._mask = None
@property
def eth(self):
"""The Ethernet address."""
return self._eth
@property
def mask(self):
"""The Ethernet address mask."""
return self._mask
def __eq__(self, other):
"""Equality operator.
Both the Ethernet address and the mask are compared. This can be used
to implement filters where we expect a specific mask to be present,
e.g: dl_dst=01:00:00:00:00:00/01:00:00:00:00:00.
Args:
other (EthMask): Another EthMask to compare against.
Returns:
True if this EthMask is the same as the other.
"""
return self._mask == other._mask and self._eth == other._eth
def __contains__(self, other):
"""Contains operator.
Args:
other (netaddr.EUI or EthMask): An Ethernet address.
Returns:
True if the other netaddr.EUI or fully-masked EthMask is
contained in this EthMask's address range.
"""
if isinstance(other, EthMask):
if other._mask:
raise ValueError(
"Comparing non fully-masked EthMask is not supported"
)
return other._eth in self
if self._mask:
return (other.value & self._mask.value) == (
self._eth.value & self._mask.value
)
else:
return other == self._eth
def __str__(self):
if self._mask:
return "/".join(
[
self._eth.format(netaddr.mac_unix),
self._mask.format(netaddr.mac_unix),
]
)
else:
return self._eth.format(netaddr.mac_unix)
def __repr__(self):
return "%s('%s')" % (self.__class__.__name__, self)
def to_json(self):
return str(self)
class IPMask(Decoder):
"""IPMask stores an IPv6 or IPv4 and a mask.
It uses netaddr.IPAddress.
IPMasks can represent valid CIDRs or randomly masked IP Addresses.
Args:
string (str): A string representing the ip/mask.
"""
def __init__(self, string):
self._ipnet = None
self._ip = None
self._mask = None
try:
self._ipnet = netaddr.IPNetwork(string)
except netaddr.AddrFormatError:
pass
if not self._ipnet:
# It's not a valid CIDR. Store ip and mask independently.
parts = string.split("/")
if len(parts) != 2:
raise ValueError(
"value {}: is not an ipv4 or ipv6 address".format(string)
)
try:
self._ip = netaddr.IPAddress(parts[0])
self._mask = netaddr.IPAddress(parts[1])
except netaddr.AddrFormatError as exc:
raise ValueError(
"value {}: is not an ipv4 or ipv6 address".format(string)
) from exc
def __eq__(self, other):
"""Equality operator.
Both the IPAddress and the mask are compared. This can be used
to implement filters where a specific mask is expected, e.g:
nw_src=192.168.1.0/24.
Args:
other (IPMask or netaddr.IPNetwork or netaddr.IPAddress):
Another IPAddress or IPNetwork to compare against.
Returns:
True if this IPMask is the same as the other.
"""
if isinstance(other, netaddr.IPNetwork):
return self._ipnet and self._ipnet == other
if isinstance(other, netaddr.IPAddress):
return self._ipnet and self._ipnet.ip == other
elif isinstance(other, IPMask):
if self._ipnet:
return self._ipnet == other._ipnet
return self._ip == other._ip and self._mask == other._mask
else:
return False
def __contains__(self, other):
"""Contains operator.
Only comparing valid CIDRs is supported.
Args:
other (netaddr.IPAddress or IPMask): An IP address.
Returns:
True if the other IPAddress is contained in this IPMask's address
range.
"""
if isinstance(other, IPMask):
if not other._ipnet:
raise ValueError("Only comparing valid CIDRs is supported")
return (
netaddr.IPAddress(other._ipnet.first) in self
and netaddr.IPAddress(other._ipnet.last) in self
)
elif isinstance(other, netaddr.IPAddress):
if self._ipnet:
return other in self._ipnet
return (other & self._mask) == (self._ip & self._mask)
def cidr(self):
"""
Returns True if the IPMask is a valid CIDR.
"""
return self._ipnet is not None
@property
def ip(self):
"""The IP address."""
if self._ipnet:
return self._ipnet.ip
return self._ip
@property
def mask(self):
"""The IP mask."""
if self._ipnet:
return self._ipnet.netmask
return self._mask
def __str__(self):
if self._ipnet:
return str(self._ipnet)
return "/".join([str(self._ip), str(self._mask)])
def __repr__(self):
return "%s('%s')" % (self.__class__.__name__, self)
def to_json(self):
return str(self)
|