alg.h File Reference

Internal, Utility More...

Go to the source code of this file.

Macros
#define	bits(n)
#define	bytes(n)
#define	offset(ptr, len)

Functions
ORDO_HIDDEN size_t	pad_check (const void *buffer, size_t len)
ORDO_HIDDEN void	xor_buffer (void *RESTRICT dst, const void *RESTRICT src, size_t len)
ORDO_HIDDEN void	inc_buffer (unsigned char *buffer, size_t len)

Detailed Description

Internal, Utility

This header provides various utility functions which are used by some library modules and a few convenience macros. It is not to be used outside the library, and this is enforced by an include guard. If you really must access it, define the ORDO_INTERNAL_ACCESS token before including it.

Macro Definition Documentation

#define bits

(

n

)

Converts bits into bytes (rounded down to the nearest byte boundary).

Remarks

As an example, bits(256) returns 32 (bytes).

#define bytes

(

n

)

Converts bytes into bits (as a multiple of 8 bits).

Remarks

As an example, bytes(32) returns 256 (bits).

#define offset	(		ptr,
			len
	)

Computes a byte-based offset.

Parameters

[in]	ptr	Base pointer.
[in]	len	Offset (in bytes).

Returns

The pointer exactly len bytes after ptr.

Remarks

This is a dangerous macro, in the sense it can lead to accessing data at unaligned addresses, and so should be used carefully.

Function Documentation

ORDO_HIDDEN size_t pad_check	(	const void *	buffer,
		size_t	len
	)

Checks whether a buffer conforms to PKCS #7 padding.

Parameters

[in]	buffer	The buffer to verify, starting at the first data byte (not at the first padding byte).
[in]	len	The length in bytes of the buffer.

Returns

The message length if the buffer is valid, or 0 otherwise. The message can therefore be recovered as the first N bytes.

Remarks

PKCS padding is defined as appending N bytes of padding data at the end of the message, each with binary value N, with N between 1 and the block size of the block cipher used such that the length of the message plus N is a multiple of the block cipher's block size.

Warning

This implies the buffer must be at least padding bytes long.

ORDO_HIDDEN void xor_buffer	(	void *RESTRICT	dst,
		const void *RESTRICT	src,
		size_t	len
	)

Performs a bitwise exclusive-or of one buffer onto another.

Parameters

[in,out]	dst	The destination buffer.
[in]	src	The source buffer.
[in]	len	The number of bytes to process.

Remarks

This is conceptually equivalent to dst ^= src.

Warning

The source and destination buffers may not overlap.

ORDO_HIDDEN void inc_buffer	(	unsigned char *	buffer,
		size_t	len
	)

Increments a buffer of arbitrary length, as though it were a len byte integer stored as a byte array.

Parameters

[in,out]	buffer	The buffer to increment in-place.
[in]	len	The size, in bytes, of the buffer.

Remarks

Carry propagation is done left-to-right.