Class: TinyDTLS::SecurityConfig

Inherits:
Object
  • Object
show all
Defined in:
lib/tinydtls/security_conf.rb

Overview

This class is used to map user identity for pre-shared keys to their actual keys. It provides an implementation of the ‘get_psk_info` function pointer used in the `dtls_handler_t` struct which is used by tinydtls to retrieve keys and identities.

The API of this class is quite strict and raises lots of exceptions because it is quite annoying to debug errors occuring in the GetPSKInfo callback.

XXX: Currently this function doesn’t map IP address to keys/identities.

Constant Summary collapse

GetPSKInfo =

Implementation of the ‘get_psk_info` function pointer as used by the `dtls_handler_t` struct.

If tinydtls requests a key for a given identity the key is returned if the identity exists. If no identity was specified the #default_key is returned.

If tinydtls requests an id the #default_id is always returned.

TODO: It would be nice to return an id depending on the ‘session_t` passad to this callback.

Proc.new do |ctx, sess, type, desc, dlen, result, rlen|
  secconf = TinyDTLS::Context.from_ptr(ctx).secconf
  if desc.null?
    key = secconf.default_key
  end

  if type == :DTLS_PSK_KEY
    key ||= secconf.get_key(desc.read_string(dlen))
    if key.nil?
      Wrapper::dtls_alert_fatal_create(
        Wrapper::Alert[:DTLS_ALERT_DECRYPT_ERROR])
    elsif key.bytesize > rlen
      Wrapper::dtls_alert_fatal_create(
        Wrapper::Alert[:DTLS_ALERT_INTERNAL_ERROR])
    else
      result.put_bytes(0, key)
      key.bytesize
    end
  elsif type == :DTLS_PSK_IDENTITY
    identity = secconf.default_id
    result.put_bytes(0, identity)
    identity.bytesize
  else
    0
  end
end

Instance Method Summary collapse

Constructor Details

#initialize ⇒ SecurityConfig

Creates a new instance of this class. At least one key/identity pair need to be added to the new instance of this class using #add_client otherwise the #default_id and #default_key methods always raise an error causing TinyDTLS handshakes to fail.



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# File 'lib/tinydtls/security_conf.rb', line 55

def initialize
  @identity_map = Hash.new
end

Instance Method Details

#add_client(id, key) ⇒ Object

Adds a security configuration for the given identity, key must be non-null otherwise a TypeError is raise.



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# File 'lib/tinydtls/security_conf.rb', line 61

def add_client(id, key)
  if key.nil?
    raise TypeError.new("Key must be non-nil")
  else
    @identity_map[id] = key
  end
end

#default_id ⇒ Object

Retrieves the default identity used for establishing new handshakes. If a #default_id hasn’t been explicitly set it returns the first identity added using #add_client.

At least one identity must have been added to the instance, otherwise this methods raises a TypeError.



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# File 'lib/tinydtls/security_conf.rb', line 83

def default_id
  if @identity_map.empty?
    raise TypeError.new("Cannot retrieve a default identity from an empty store")
  end

  if @default_id.nil?
    @identity_map.to_a.first.first
  else
    @default_id
  end
end

#default_id=(id) ⇒ Object

Changes the default identity, the given identity must already exist in the store.



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# File 'lib/tinydtls/security_conf.rb', line 97

def default_id=(id)
  if @identity_map.has_key? id
    @default_id = id
  else
    raise TypeError.new("Default identity must already exist")
  end
end

#default_key ⇒ Object

Retrieves the default key used when a call to #GetPSKInfo didn’t specify a key. If a #default_key hasn’t been explicitly set it returns the first key added using #add_client.

At least one key must have been added to the instance, otherwise this methods raises a TypeError.



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# File 'lib/tinydtls/security_conf.rb', line 111

def default_key
  if @identity_map.empty?
    raise TypeError.new("Cannot retrieve a default key from an empty store")
  end

  if @default_key.nil?
    @identity_map.to_a.first.last
  else
    @default_key
  end
end

#default_key=(key) ⇒ Object

Changes the default key, the given key must already exist in the store.



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# File 'lib/tinydtls/security_conf.rb', line 124

def default_key=(key)
  if @identity_map.key(key)
    @default_key = key
  else
    raise TypeError.new("Default key must already exist")
  end
end

#get_key(id) ⇒ Object

Retrieves the key associated with the given identity, nil is returned if no key was specified for the given identity.



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# File 'lib/tinydtls/security_conf.rb', line 71

def get_key(id)
  if @identity_map.has_key? id
    @identity_map[id]
  end
end

#set_defaults(id, key) ⇒ Object

Sets the #default_id and #default_key, restrictions mentioned in #default_id= and #default_key= apply.



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# File 'lib/tinydtls/security_conf.rb', line 134

def set_defaults(id, key)
  default_id = id
  default_key = key
end