class Dnsruby::Dnssec

RFC4033, section 7

"There is one more step that a security-aware stub resolver can take
if, for whatever reason, it is not able to establish a useful trust
relationship with the recursive name servers that it uses: it can
perform its own signature validation by setting the Checking Disabled
(CD) bit in its query messages.  A validating stub resolver is thus
able to treat the DNSSEC signatures as trust relationships between
the zone administrators and the stub resolver itself. "

Dnsruby is configured to validate responses by default. However, it is not configured with any trusted keys by default. Applications may use the verify() method to perform verification with of RRSets of Messages with given keys. Alternatively, trusted keys may be added to this class (either directly, or by loading the IANA TAR or the DLV ISC ZSK). Validation will then be performed from these keys (or the DLV registry, if configured). Negative and positive responses are validation.

Messages are tagged with the current security_level (Message::SecurityLevel). UNCHECKED means Dnsruby has not attempted to validate the response. BOGUS means the response has been checked, and is bogus. INSECURE means the response has been validated to be insecure (e.g. in an unsigned zone) SECURE means that the response has been verfied to be correct.

Several validators are provided, with each maintaining its own cache of trusted keys. If validators are added or removed, the caches of the other validators are not affected.

Public Class Methods

add_dlv_key(dlv_key) click to toggle source

Add a trusted Key Signing Key for the ISC DLV registry.

# File lib/dnsruby/dnssec.rb, line 94
def Dnssec.add_dlv_key(dlv_key)
  @@dlv_verifier.add_dlv_key(dlv_key)
end
add_trust_anchor(t) click to toggle source

Add a new trust anchor

# File lib/dnsruby/dnssec.rb, line 98
def Dnssec.add_trust_anchor(t)
  #  @TODO@ Create a new verifier?
  @@anchor_verifier.add_trust_anchor(t)
end
add_trust_anchor_with_expiration(k, expiration) click to toggle source

Add the trusted key with the given expiration time

# File lib/dnsruby/dnssec.rb, line 103
def self.add_trust_anchor_with_expiration(k, expiration)
  #  Create a new verifier?
  @@anchor_verifier.add_trust_anchor_with_expiration(k, expiration)
end
anchor_verifier() click to toggle source
# File lib/dnsruby/dnssec.rb, line 301
def self.anchor_verifier
  return @@anchor_verifier
end
clear_trust_anchors() click to toggle source

Wipes the cache of trusted keys

# File lib/dnsruby/dnssec.rb, line 112
def self.clear_trust_anchors
  @@anchor_verifier.clear_trust_anchors
end
clear_trusted_keys() click to toggle source
# File lib/dnsruby/dnssec.rb, line 120
def self.clear_trusted_keys
  [@@anchor_verifier, @@root_verifier, @@dlv_verifier].each {|v|
    v.clear_trusted_keys
  }
end
default_resolver() click to toggle source
# File lib/dnsruby/dnssec.rb, line 175
def self.default_resolver
  return @@default_resolver
end
default_resolver=(res) click to toggle source

This method overrides the system default resolver configuration for validation If default_resolver is set, then it will be used to follow the chain of trust. If it is not, then the default system resolver will be used (unless do_validation_with_recursor is set.

# File lib/dnsruby/dnssec.rb, line 172
def self.default_resolver=(res)
  @@default_resolver = res
end
dlv_verifier() click to toggle source
# File lib/dnsruby/dnssec.rb, line 304
def self.dlv_verifier
  return @@dlv_verifier
end
do_validation_with_recursor(on) click to toggle source

This method defines the choice of Resolver or Recursor, when the validator is checking responses. If set to true, then a Recursor will be used to query for the DNSSEC records. Otherwise, the default system resolver will be used.

# File lib/dnsruby/dnssec.rb, line 162
def self.do_validation_with_recursor(on)
  @@do_validation_with_recursor = on
end
do_validation_with_recursor?() click to toggle source
# File lib/dnsruby/dnssec.rb, line 165
def self.do_validation_with_recursor?
  return @@do_validation_with_recursor
end
no_keys?() click to toggle source
# File lib/dnsruby/dnssec.rb, line 145
def self.no_keys?
  no_keys = true
  [@@anchor_verifier, @@root_verifier, @@dlv_verifier].each {|v|
    if (v.trusted_keys.length() > 0 ||
          v.trust_anchors.length() > 0)
      no_keys = false
    end
  }
  return no_keys
end
remove_trust_anchor(t) click to toggle source

Remove the trusted key

# File lib/dnsruby/dnssec.rb, line 108
def Dnssec.remove_trust_anchor(t)
  @@anchor_verifier.remove_trust_anchor(t)
end
reset() click to toggle source
# File lib/dnsruby/dnssec.rb, line 126
def self.reset
  @@validation_policy = ValidationPolicy::LOCAL_ANCHORS_THEN_ROOT
  @@root_verifier = SingleVerifier.new(SingleVerifier::VerifierType::ROOT)
  @@root_verifier.add_root_ds(@@root_key)
  @@root_verifier.add_root_ds(@@root_key_new)

  @@dlv_verifier = SingleVerifier.new(SingleVerifier::VerifierType::DLV)

  #  @TODO@ Could add a new one of these for each anchor.
  @@anchor_verifier = SingleVerifier.new(SingleVerifier::VerifierType::ANCHOR)
  @@do_validation_with_recursor = true # Many nameservers don't handle DNSSEC correctly yet
  @@default_resolver = Resolver.new
end
root_verifier() click to toggle source
# File lib/dnsruby/dnssec.rb, line 307
def self.root_verifier
  return @@root_verifier
end
set_hints(hints) click to toggle source
# File lib/dnsruby/dnssec.rb, line 140
def self.set_hints(hints)
  @@root_verifier.set_hints(hints)
  @@anchor_verifier.set_hints(hints)
end
trust_anchors() click to toggle source
# File lib/dnsruby/dnssec.rb, line 116
def self.trust_anchors
  return @@anchor_verifier.trust_anchors
end
validate(msg) click to toggle source

Returns true for secure/insecure, false otherwise This method will set the security_level on msg to the appropriate value. Could be : secure, insecure, bogus or indeterminate If an error is encountered during verification, then the thrown exception will define the error.

# File lib/dnsruby/dnssec.rb, line 184
def self.validate(msg)
  query = Message.new()
  query.header.cd=true
  return self.validate_with_query(query, msg)
end
validate_with_anchors(msg, query) click to toggle source
# File lib/dnsruby/dnssec.rb, line 277
def self.validate_with_anchors(msg, query)
  return @@anchor_verifier.validate(msg, query)
end
validate_with_dlv(msg, query) click to toggle source
# File lib/dnsruby/dnssec.rb, line 285
def self.validate_with_dlv(msg, query)
  return @@dlv_verifier.validate(msg, query)
end
validate_with_query(query, msg) click to toggle source
# File lib/dnsruby/dnssec.rb, line 190
def self.validate_with_query(query, msg)
  if (!msg)
    return false
  end
  #  First, just check there is something to validate!
  found_sigs = false
  msg.each_resource {|rr|
    if (rr.type == Types::RRSIG)
      found_sigs = true
    end
  }
  if (found_sigs)
    begin
      if (verify(msg))
        msg.security_level = Message::SecurityLevel.SECURE
        return true
      end
    rescue VerifyError => e
      msg.security_error = e
      msg.security_level = Message::SecurityLevel.BOGUS
    end
  end

  #  SHOULD ALWAYS VERIFY DNSSEC-SIGNED RESPONSES?
  #  Yes - if a trust anchor is configured. Otherwise, act on CD bit (in query)
  TheLog.debug("Checking whether to validate, query.cd = #{query.header.cd}")
  if (((@@validation_policy > ValidationPolicy::ALWAYS_ROOT_ONLY) && (self.trust_anchors().length > 0)) ||
        #  Check query here, and validate if CD is true
      ((query.header.cd == true))) # && (query.do_validation)))
    TheLog.debug("Starting validation")

    #  Validate!
    #  Need to think about trapping/storing exceptions and security_levels here
    last_error = ""
    last_level = Message::SecurityLevel.BOGUS
    last_error_level = Message::SecurityLevel.BOGUS
    if (@@validation_policy == ValidationPolicy::ALWAYS_LOCAL_ANCHORS_ONLY)
      last_level, last_error, last_error_level = try_validation(last_level, last_error, last_error_level,
        Proc.new{|m, q| validate_with_anchors(m, q)}, msg, query)
    elsif (@@validation_policy == ValidationPolicy::ALWAYS_ROOT_ONLY)
      last_level, last_error, last_error_level = try_validation(last_level, last_error, last_error_level,
        Proc.new{|m, q| validate_with_root(m, q)}, msg, query)
    elsif (@@validation_policy == ValidationPolicy::LOCAL_ANCHORS_THEN_ROOT)
      last_level, last_error, last_error_level = try_validation(last_level, last_error, last_error_level,
        Proc.new{|m, q| validate_with_anchors(m, q)}, msg, query)
      if (last_level != Message::SecurityLevel.SECURE)
        last_level, last_error, last_error_level = try_validation(last_level, last_error, last_error_level,
          Proc.new{|m, q| validate_with_root(m, q)}, msg, query)
      end
    elsif (@@validation_policy == ValidationPolicy::ROOT_THEN_LOCAL_ANCHORS)
      last_level, last_error, last_error_level = try_validation(last_level, last_error, last_error_level,
        Proc.new{|m, q| validate_with_root(m, q)}, msg, query)
      if (last_level != Message::SecurityLevel.SECURE)
        last_level, last_error, last_error_level = try_validation(last_level, last_error, last_error_level,
          Proc.new{|m, q| validate_with_anchors(m, q)}, msg, query)
      end
    end
    if (last_level != Message::SecurityLevel.SECURE && last_level != Message::SecurityLevel.BOGUS)
      last_level, last_error, last_error_level = try_validation(last_level, last_error, last_error_level,
        Proc.new{|m, q| validate_with_dlv(m, q)}, msg, query)
    end
    #  Set the message security level!
    msg.security_level = last_level
    msg.security_error = last_error
    if (last_error && last_error.index("ification error"))
      msg.security_level = Message::SecurityLevel.BOGUS
    end
    raise VerifyError.new(last_error) if (last_level < 0)
    return (msg.security_level.code > Message::SecurityLevel::UNCHECKED)
  end
  msg.security_level = Message::SecurityLevel.UNCHECKED
  return true
end
validate_with_root(msg, query) click to toggle source
# File lib/dnsruby/dnssec.rb, line 281
def self.validate_with_root(msg, query)
  return @@root_verifier.validate(msg, query)
end
validation_policy() click to toggle source
# File lib/dnsruby/dnssec.rb, line 73
def Dnssec.validation_policy
  @@validation_policy
end
validation_policy=(p) click to toggle source
# File lib/dnsruby/dnssec.rb, line 67
def Dnssec.validation_policy=(p)
  if ((p >= ValidationPolicy::ALWAYS_ROOT_ONLY) && (p <= ValidationPolicy::ALWAYS_LOCAL_ANCHORS_ONLY))
    @@validation_policy = p
    #  @TODO@ Should we be clearing the trusted keys now?
  end
end
verify(msg, keys=nil) click to toggle source
# File lib/dnsruby/dnssec.rb, line 289
def self.verify(msg, keys=nil)
  begin
    return true if @@anchor_verifier.verify(msg, keys)
  rescue VerifyError
    begin
      return true if @@root_verifier.verify(msg, keys)
    rescue VerifyError
      return true if @@dlv_verifier.verify(msg, keys) # Will carry error to client
    end
  end
end
verify_rrset(rrset, keys = nil) click to toggle source
# File lib/dnsruby/dnssec.rb, line 314
def self.verify_rrset(rrset, keys = nil)
  return ((@@anchor_verifier.verify_rrset(rrset, keys) ||
        @@root_verifier.verify_rrset(rrset, keys) ||
        @@dlv_verifier.verify_rrset(rrset, keys)))
end