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openntpd-openbsd
mirror of https://github.com/Fincer/openntpd-openbsd


.\"	$OpenBSD: SHA256Init.3,v 1.3 2019/12/04 19:01:49 jmc Exp $

.\"

.\" Copyright (c) 2003, 2004 Todd C. Miller <millert@openbsd.org>

.\"

.\" Permission to use, copy, modify, and distribute this software for any

.\" purpose with or without fee is hereby granted, provided that the above

.\" copyright notice and this permission notice appear in all copies.

.\"

.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

.\"

.\" Sponsored in part by the Defense Advanced Research Projects

.\" Agency (DARPA) and Air Force Research Laboratory, Air Force

.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.

.\"

.\" See http://www.nist.gov/sha/ for the detailed standard

.\"

.Dd $Mdocdate: December 4 2019 $

.Dt SHA256INIT 3

.Os

.Sh NAME

.Nm SHA224Init ,

.Nm SHA224Update ,

.Nm SHA224Pad ,

.Nm SHA224Final ,

.Nm SHA224Transform ,

.Nm SHA224End ,

.Nm SHA224File ,

.Nm SHA224FileChunk ,

.Nm SHA224Data ,

.Nm SHA256Init ,

.Nm SHA256Update ,

.Nm SHA256Pad ,

.Nm SHA256Final ,

.Nm SHA256Transform ,

.Nm SHA256End ,

.Nm SHA256File ,

.Nm SHA256FileChunk ,

.Nm SHA256Data ,

.Nm SHA384Init ,

.Nm SHA384Update ,

.Nm SHA384Pad ,

.Nm SHA384Final ,

.Nm SHA384Transform ,

.Nm SHA384End ,

.Nm SHA384File ,

.Nm SHA384FileChunk ,

.Nm SHA384Data ,

.Nm SHA512Init ,

.Nm SHA512Update ,

.Nm SHA512Pad ,

.Nm SHA512Final ,

.Nm SHA512Transform ,

.Nm SHA512End ,

.Nm SHA512File ,

.Nm SHA512FileChunk ,

.Nm SHA512Data ,

.Nm SHA512_256Init ,

.Nm SHA512_256Update ,

.Nm SHA512_256Pad ,

.Nm SHA512_256Final ,

.Nm SHA512_256Transform ,

.Nm SHA512_256End ,

.Nm SHA512_256File ,

.Nm SHA512_256FileChunk ,

.Nm SHA512_256Data

.Nd calculate the NIST Secure Hash Standard (version 2)

.Sh SYNOPSIS

.In sys/types.h

.In sha2.h

.Ft void

.Fn SHA224Init "SHA2_CTX *context"

.Ft void

.Fn SHA224Update "SHA2_CTX *context" "const u_int8_t *data" "size_t len"

.Ft void

.Fn SHA224Pad "SHA2_CTX *context"

.Ft void

.Fn SHA224Final "u_int8_t digest[SHA224_DIGEST_LENGTH]" "SHA2_CTX *context"

.Ft void

.Fn SHA224Transform "u_int32_t state[8]" "const u_int8_t buffer[SHA224_BLOCK_LENGTH]"

.Ft "char *"

.Fn SHA224End "SHA2_CTX *context" "char *buf"

.Ft "char *"

.Fn SHA224File "const char *filename" "char *buf"

.Ft "char *"

.Fn SHA224FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"

.Ft "char *"

.Fn SHA224Data "const u_int8_t *data" "size_t len" "char *buf"

.Ft void

.Fn SHA256Init "SHA2_CTX *context"

.Ft void

.Fn SHA256Update "SHA2_CTX *context" "const u_int8_t *data" "size_t len"

.Ft void

.Fn SHA256Pad "SHA2_CTX *context"

.Ft void

.Fn SHA256Final "u_int8_t digest[SHA256_DIGEST_LENGTH]" "SHA2_CTX *context"

.Ft void

.Fn SHA256Transform "u_int32_t state[8]" "const u_int8_t buffer[SHA256_BLOCK_LENGTH]"

.Ft "char *"

.Fn SHA256End "SHA2_CTX *context" "char *buf"

.Ft "char *"

.Fn SHA256File "const char *filename" "char *buf"

.Ft "char *"

.Fn SHA256FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"

.Ft "char *"

.Fn SHA256Data "const u_int8_t *data" "size_t len" "char *buf"

.Ft void

.Fn SHA384Init "SHA2_CTX *context"

.Ft void

.Fn SHA384Update "SHA2_CTX *context" "const u_int8_t *data" "size_t len"

.Ft void

.Fn SHA384Pad "SHA2_CTX *context"

.Ft void

.Fn SHA384Final "u_int8_t digest[SHA384_DIGEST_LENGTH]" "SHA2_CTX *context"

.Ft void

.Fn SHA384Transform "u_int64_t state[8]" "const u_int8_t buffer[SHA384_BLOCK_LENGTH]"

.Ft "char *"

.Fn SHA384End "SHA2_CTX *context" "char *buf"

.Ft "char *"

.Fn SHA384File "const char *filename" "char *buf"

.Ft "char *"

.Fn SHA384FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"

.Ft "char *"

.Fn SHA384Data "const u_int8_t *data" "size_t len" "char *buf"

.Ft void

.Fn SHA512Init "SHA2_CTX *context"

.Ft void

.Fn SHA512Update "SHA2_CTX *context" "const u_int8_t *data" "size_t len"

.Ft void

.Fn SHA512Pad "SHA2_CTX *context"

.Ft void

.Fn SHA512Final "u_int8_t digest[SHA512_DIGEST_LENGTH]" "SHA2_CTX *context"

.Ft void

.Fn SHA512Transform "u_int64_t state[8]" "const u_int8_t buffer[SHA512_BLOCK_LENGTH]"

.Ft "char *"

.Fn SHA512End "SHA2_CTX *context" "char *buf"

.Ft "char *"

.Fn SHA512File "const char *filename" "char *buf"

.Ft "char *"

.Fn SHA512FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"

.Ft "char *"

.Fn SHA512Data "const u_int8_t *data" "size_t len" "char *buf"

.Ft void

.Fn SHA512_256Init "SHA2_CTX *context"

.Ft void

.Fn SHA512_256Update "SHA2_CTX *context" "const u_int8_t *data" "size_t len"

.Ft void

.Fn SHA512_256Pad "SHA2_CTX *context"

.Ft void

.Fn SHA512_256Final "u_int8_t digest[SHA512_256_DIGEST_LENGTH]" "SHA2_CTX *context"

.Ft void

.Fn SHA512_256Transform "u_int64_t state[8]" "const u_int8_t buffer[SHA512_256_BLOCK_LENGTH]"

.Ft "char *"

.Fn SHA512_256End "SHA2_CTX *context" "char *buf"

.Ft "char *"

.Fn SHA512_256File "const char *filename" "char *buf"

.Ft "char *"

.Fn SHA512_256FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"

.Ft "char *"

.Fn SHA512_256Data "const u_int8_t *data" "size_t len" "char *buf"

.Sh DESCRIPTION

The SHA2 functions implement the NIST Secure Hash Standard,

FIPS PUB 180-2.

The SHA2 functions are used to generate a condensed representation of a

message called a message digest, suitable for use as a digital signature.

There are four families of functions, with names corresponding to

the number of bits in the resulting message digest.

The SHA-224 and SHA-256 functions are limited to processing a message of less

than 2^64 bits as input.

The SHA-384 and SHA-512 functions can process a message of at most 2^128 - 1

bits as input.

.Pp

The SHA2 functions are considered to be more secure than the SHA1 functions,

with which they share a similar interface.

The 224, 256, 384, and 512-bit versions of SHA2 share the same interface.

SHA512/256, a truncated version of SHA512, is also supported.

For brevity, only the 256-bit variants are described below.

.Pp

The

.Fn SHA256Init

function initializes a SHA2_CTX

.Fa context

for use with

.Fn SHA256Update

and

.Fn SHA256Final .

The

.Fn SHA256Update

function adds

.Fa data

of length

.Fa len

to the SHA2_CTX specified by

.Fa context .

.Fn SHA256Final

is called when all data has been added via

.Fn SHA256Update

and stores a message digest in the

.Fa digest

parameter.

.Pp

The

.Fn SHA256Pad

function can be used to apply padding to the message digest as in

.Fn SHA256Final ,

but the current context can still be used with

.Fn SHA256Update .

.Pp

The

.Fn SHA256Transform

function is used by

.Fn SHA256Update

to hash 512-bit blocks and forms the core of the algorithm.

Most programs should use the interface provided by

.Fn SHA256Init ,

.Fn SHA256Update ,

and

.Fn SHA256Final

instead of calling

.Fn SHA256Transform

directly.

.Pp

The

.Fn SHA256End

function is a front end for

.Fn SHA256Final

which converts the digest into an ASCII representation

of the digest in hexadecimal.

.Pp

The

.Fn SHA256File

function calculates the digest for a file and returns the result via

.Fn SHA256End .

If

.Fn SHA256File

is unable to open the file, a

.Dv NULL

pointer is returned.

.Pp

.Fn SHA256FileChunk

behaves like

.Fn SHA256File

but calculates the digest only for that portion of the file starting at

.Fa offset

and continuing for

.Fa length

bytes or until end of file is reached, whichever comes first.

A zero

.Fa length

can be specified to read until end of file.

A negative

.Fa length

or

.Fa offset

will be ignored.

.Pp

The

.Fn SHA256Data

function

calculates the digest of an arbitrary string and returns the result via

.Fn SHA256End .

.Pp

For each of the

.Fn SHA256End ,

.Fn SHA256File ,

.Fn SHA256FileChunk ,

and

.Fn SHA256Data

functions the

.Fa buf

parameter should either be a string large enough to hold the resulting digest

(e.g.\&

.Dv SHA224_DIGEST_STRING_LENGTH ,

.Dv SHA256_DIGEST_STRING_LENGTH ,

.Dv SHA384_DIGEST_STRING_LENGTH ,

.Dv SHA512_DIGEST_STRING_LENGTH ,

or

.Dv SHA512_256_DIGEST_STRING_LENGTH ,

depending on the function being used)

or a

.Dv NULL

pointer.

In the latter case, space will be dynamically allocated via

.Xr malloc 3

and should be freed using

.Xr free 3

when it is no longer needed.

.Sh EXAMPLES

The following code fragment will calculate the SHA-256 digest for the string

.Qq abc ,

which is

.Dq 0xba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad .

.Bd -literal -offset indent

SHA2_CTX ctx;

u_int8_t results[SHA256_DIGEST_LENGTH];

char *buf;

int n;


buf = "abc";

n = strlen(buf);

SHA256Init(&ctx);

SHA256Update(&ctx, (u_int8_t *)buf, n);

SHA256Final(results, &ctx);


/* Print the digest as one long hex value */

printf("0x");

for (n = 0; n \*(Lt SHA256_DIGEST_LENGTH; n++)

	printf("%02x", results[n]);

putchar('\en');

.Ed

.Pp

Alternately, the helper functions could be used in the following way:

.Bd -literal -offset indent

u_int8_t output[SHA256_DIGEST_STRING_LENGTH];

char *buf = "abc";


printf("0x%s\en", SHA256Data(buf, strlen(buf), output));

.Ed

.Sh SEE ALSO

.Xr cksum 1 ,

.Xr sha256 1 ,

.Xr MD5Init 3 ,

.Xr RMD160Init 3 ,

.Xr SHA1Init 3

.Rs

.%T Secure Hash Standard

.%O FIPS PUB 180-2

.Re

.Sh HISTORY

The SHA2 functions appeared in

.Ox 3.4 .

.Sh AUTHORS

.An -nosplit

This implementation of the SHA functions was written by

.An Aaron D. Gifford .

.Pp

The

.Fn SHA256End ,

.Fn SHA256File ,

.Fn SHA256FileChunk ,

and

.Fn SHA256Data

helper functions are derived from code written by

								.An Poul-Henning Kamp .