| Copyright | (c) Piyush P Kurur 2019 |
|---|---|
| License | Apache-2.0 OR BSD-3-Clause |
| Maintainer | Piyush P Kurur <ppk@iitpkd.ac.in> |
| Stability | experimental |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Raaz.Core.Memory
Description
Synopsis
- class Memory m where
- memoryAlloc :: Alloc m
- unsafeToPointer :: m -> Ptr Word8
- data VoidMemory
- withMemoryPtr :: Memory m => (BYTES Int -> Ptr Word8 -> IO a) -> m -> IO a
- withMemory :: Memory mem => (mem -> IO a) -> IO a
- withSecureMemory :: Memory mem => (mem -> IO a) -> IO a
- type Alloc mem = TwistRF AllocField (BYTES Int) mem
- pointerAlloc :: LengthUnit l => l -> Alloc (Ptr Word8)
- class Memory m => Initialisable m v where
- initialise :: v -> m -> IO ()
- class Memory m => Extractable m v where
- modifyMem :: (Initialisable mem a, Extractable mem b) => (b -> a) -> mem -> IO ()
- data Access = Access {}
- class Memory mem => ReadAccessible mem where
- beforeReadAdjustment :: mem -> IO ()
- readAccess :: mem -> [Access]
- class Memory mem => WriteAccessible mem where
- writeAccess :: mem -> [Access]
- afterWriteAdjustment :: mem -> IO ()
- memTransfer :: (ReadAccessible src, WriteAccessible dest) => Dest dest -> Src src -> IO ()
- data MemoryCell a
- copyCell :: Storable a => Dest (MemoryCell a) -> Src (MemoryCell a) -> IO ()
- withCellPointer :: Storable a => (Ptr a -> IO b) -> MemoryCell a -> IO b
- unsafeGetCellPointer :: Storable a => MemoryCell a -> Ptr a
Low level memory management in raaz.
Warning: This module is pretty low level and should not be needed in typical use cases. Only developers of protocols and primitives might have a reason to look into this module.
The memory subsytem of raaz gives a relatively abstract and type
safe interface for performing low level size calculations and
pointer arithmetic. The two main components of this subsystem
is the class Memory whose instances are essentially memory buffers that
are distinguished at the type level, and the type Alloc that captures
the allocation strategies for these types.
The memory class
Any cryptographic primitives use memory to store stuff. This class abstracts all types that hold some memory. Cryptographic application often requires securing the memory from being swapped out (think of memory used to store private keys or passwords). This abstraction supports memory securing. If your platform supports memory locking, then securing a memory will prevent the memory from being swapped to the disk. Once secured the memory location is overwritten by nonsense before being freed.
While some basic memory elements like MemoryCell are exposed from
the library, often we require compound memory objects built out of
simpler ones. The Applicative instance of the Alloc can be made
use of in such situation to simplify such instance declaration as
illustrated in the instance declaration for a pair of memory
elements.
instance (Memory ma, Memory mb) => Memory (ma, mb) where memoryAlloc = (,) <$> memoryAlloc <*> memoryAlloc unsafeToPointer (ma, _) = unsafeToPointer ma
Methods
memoryAlloc :: Alloc m Source #
Returns an allocator for this memory.
unsafeToPointer :: m -> Ptr Word8 Source #
Returns the pointer to the underlying buffer.
Instances
data VoidMemory Source #
A memory element that holds nothing.
Instances
| Memory VoidMemory Source # | |
Defined in Raaz.Core.Memory | |
withMemoryPtr :: Memory m => (BYTES Int -> Ptr Word8 -> IO a) -> m -> IO a Source #
Apply some low level action on the underlying buffer of the memory.
withMemory :: Memory mem => (mem -> IO a) -> IO a Source #
Perform an action which makes use of this memory. The memory allocated will automatically be freed when the action finishes either gracefully or with some exception. Besides being safer, this method might be more efficient as the memory might be allocated from the stack directly and will have very little GC overhead.
withSecureMemory :: Memory mem => (mem -> IO a) -> IO a Source #
Similar to withMemory but allocates a secure memory for the
action. Secure memories are never swapped on to disk and will be
wiped clean of sensitive data after use. However, be careful when
using this function in a child thread. Due to the daemonic nature
of Haskell threads, if the main thread exists before the child
thread is done with its job, sensitive data can leak. This is
essentially a limitation of the bracket which is used internally.
The allocator
type Alloc mem = TwistRF AllocField (BYTES Int) mem Source #
A memory allocator for the memory type mem. The Applicative
instance of Alloc can be used to build allocations for
complicated memory elements from simpler ones and takes care of
handling the size/offset calculations involved.
pointerAlloc :: LengthUnit l => l -> Alloc (Ptr Word8) Source #
Allocates a buffer of size l and returns the pointer to it pointer.
Initialisation and Extraction.
Memories often allow initialisation with and extraction of values
in the Haskell world. The Initialisable and Extractable class
captures this interface.
Explicit Pointer
Using the Initialisable and Extractable for sensitive data
interface defeats one important purpose of the memory subsystem
namely providing memory locking. Using these interfaces means
keeping the sensitive information as pure values in the Haskell
heap which impossible to lock. Worse still, the GC often move the
data around spreading it all around the memory. One should use
direct byte transfer via memcpy for effecting these
initialisation. An interface to facilitate these is the type
classes ReadAccessible and WriteAccessble where direct access
is given (via the Access buffer) to the portions of the internal
memory where sensitive data is kept.
class Memory m => Initialisable m v where Source #
Memories that can be initialised with a pure value. The pure
value resides in the Haskell heap and hence can potentially be
swapped. Therefore, this class should be avoided if compromising
the initialisation value can be dangerous. Look into the type class
WriteAccessible instead.
Methods
initialise :: v -> m -> IO () Source #
Instances
class Memory m => Extractable m v where Source #
Memories from which pure values can be extracted. Much like the
case of the Initialisable class, avoid using this interface if
you do not want the data extracted to be swapped. Use the
ReadAccessible class instead.
Instances
| Extractable ChaCha20Mem (BlockCount ChaCha20) Source # | |
Defined in Raaz.Primitive.ChaCha20.Internal Methods extract :: ChaCha20Mem -> IO (BlockCount ChaCha20) Source # | |
| Storable a => Extractable (MemoryCell a) a Source # | |
Defined in Raaz.Core.Memory Methods extract :: MemoryCell a -> IO a Source # | |
| Storable h => Extractable (HashMemory128 h) h Source # | |
Defined in Raaz.Primitive.HashMemory Methods extract :: HashMemory128 h -> IO h Source # | |
| Storable h => Extractable (HashMemory64 h) h Source # | |
Defined in Raaz.Primitive.HashMemory Methods extract :: HashMemory64 h -> IO h Source # | |
modifyMem :: (Initialisable mem a, Extractable mem b) => (b -> a) -> mem -> IO () Source #
Apply the given function to the value in the cell. For a function
f :: b -> a, the action modify f first extracts a value of type
b from the memory element, applies f to it and puts the result
back into the memory.
modifyMem f mem = do b <- extract mem
initialise (f b) memAccessing the bytes directly
To avoid the problems associated with the Initialisable and
Extractable interface, certain memory types give access to the
associated buffers directly via the Access buffer. Data then
needs to be transferred between these memories directly via
memcpy making use of the Access buffers thereby avoiding a copy
in the Haskell heap where it is prone to leak.
ReadAccessible:- Instances of these class are memories that are on the source side of the transfer. Examples include the memory element that is used to implement a Diffie-Hellman key exchange. The exchanged key is in the memory which can then be used to initialise a cipher for the actual transfer of encrypted data .
WriteAccessible:- Instances of these classes are memories that are on the destination side of the transfer. The memory element that stores the key for a cipher is an example of such a element.
Data type that gives an access buffer to portion of the memory.
class Memory mem => ReadAccessible mem where Source #
This class captures memories from which bytes can be extracted directly from (portions of) its buffer.
Methods
beforeReadAdjustment :: mem -> IO () Source #
Internal organisation of the data might need adjustment due to
host machine having a different endian than the standard byte
order of the associated type. This action perform the necessary
adjustment before the bytes can be read-off from the associated
readAccess adjustments.
readAccess :: mem -> [Access] Source #
The ordered access buffers for the memory through which bytes
may be read off (after running beforeReadAdjustment of course)
Instances
| EndianStore a => ReadAccessible (MemoryCell a) Source # | |
Defined in Raaz.Core.Memory Methods beforeReadAdjustment :: MemoryCell a -> IO () Source # readAccess :: MemoryCell a -> [Access] Source # | |
class Memory mem => WriteAccessible mem where Source #
This class captures memories that can be initialised by writing bytes to (portions of) its buffer.
Methods
writeAccess :: mem -> [Access] Source #
The ordered access to buffers through which bytes may be written into the memory.
afterWriteAdjustment :: mem -> IO () Source #
After writing data into the buffer, the memory might need further adjustments before it is considered "initialised" with the sensitive data.
Instances
| WriteAccessible ChaCha20Mem Source # | Writes into the key portion. |
Defined in Raaz.Primitive.ChaCha20.Internal Methods writeAccess :: ChaCha20Mem -> [Access] Source # afterWriteAdjustment :: ChaCha20Mem -> IO () Source # | |
| EndianStore a => WriteAccessible (MemoryCell a) Source # | |
Defined in Raaz.Core.Memory Methods writeAccess :: MemoryCell a -> [Access] Source # afterWriteAdjustment :: MemoryCell a -> IO () Source # | |
memTransfer :: (ReadAccessible src, WriteAccessible dest) => Dest dest -> Src src -> IO () Source #
Transfer the bytes from the source memory to the destination memory. The total bytes transferred is the minimum of the bytes available at the source and the space available at the destination.
A basic memory cell.
data MemoryCell a Source #
A memory location to store a value of type having Storable
instance.
Instances
copyCell :: Storable a => Dest (MemoryCell a) -> Src (MemoryCell a) -> IO () Source #
Copy the contents of one memory cell to another.
withCellPointer :: Storable a => (Ptr a -> IO b) -> MemoryCell a -> IO b Source #
Work with the underlying pointer of the memory cell. Useful while working with ffi functions.
unsafeGetCellPointer :: Storable a => MemoryCell a -> Ptr a Source #
The location where the actual storing of element happens. This
pointer is guaranteed to be aligned to the alignment restriction of a