1.\" 2.\" ---------------------------------------------------------------------------- 3.\" "THE BEER-WARE LICENSE" (Revision 42): 4.\" <phk@FreeBSD.org> wrote this file. As long as you retain this notice you 5.\" can do whatever you want with this stuff. If we meet some day, and you think 6.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp 7.\" ---------------------------------------------------------------------------- 8.\" 9.\" From: Id: mdX.3,v 1.14 1999/02/11 20:31:49 wollman Exp 10.\" $FreeBSD$ 11.\" 12.Dd July 20, 2018 13.Dt SHA 3 14.Os 15.Sh NAME 16.Nm SHA_Init , 17.Nm SHA_Update , 18.Nm SHA_Final , 19.Nm SHA_End , 20.Nm SHA_File , 21.Nm SHA_FileChunk , 22.Nm SHA_Data , 23.Nm SHA1_Init , 24.Nm SHA1_Update , 25.Nm SHA1_Final , 26.Nm SHA1_End , 27.Nm SHA1_File , 28.Nm SHA1_FileChunk , 29.Nm SHA1_Data 30.Nd calculate the FIPS 160 and 160-1 ``SHA'' message digests 31.Sh LIBRARY 32.Lb libmd 33.Sh SYNOPSIS 34.In sys/types.h 35.In sha.h 36.Ft void 37.Fn SHA_Init "SHA_CTX *context" 38.Ft void 39.Fn SHA_Update "SHA_CTX *context" "const unsigned char *data" "size_t len" 40.Ft void 41.Fn SHA_Final "unsigned char digest[20]" "SHA_CTX *context" 42.Ft "char *" 43.Fn SHA_End "SHA_CTX *context" "char *buf" 44.Ft "char *" 45.Fn SHA_File "const char *filename" "char *buf" 46.Ft "char *" 47.Fn SHA_FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length" 48.Ft "char *" 49.Fn SHA_Data "const unsigned char *data" "unsigned int len" "char *buf" 50.Ft void 51.Fn SHA1_Init "SHA_CTX *context" 52.Ft void 53.Fn SHA1_Update "SHA_CTX *context" "const unsigned char *data" "size_t len" 54.Ft void 55.Fn SHA1_Final "unsigned char digest[20]" "SHA_CTX *context" 56.Ft "char *" 57.Fn SHA1_End "SHA_CTX *context" "char *buf" 58.Ft "char *" 59.Fn SHA1_File "const char *filename" "char *buf" 60.Ft "char *" 61.Fn SHA1_FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length" 62.Ft "char *" 63.Fn SHA1_Data "const unsigned char *data" "unsigned int len" "char *buf" 64.Sh DESCRIPTION 65The 66.Li SHA_ 67and 68.Li SHA1_ 69functions calculate a 160-bit cryptographic checksum (digest) 70for any number of input bytes. 71A cryptographic checksum is a one-way 72hash function; that is, it is computationally impractical to find 73the input corresponding to a particular output. 74This net result is 75a 76.Dq fingerprint 77of the input-data, which does not disclose the actual input. 78.Pp 79.Tn SHA 80(or 81.Tn SHA-0 ) 82is the original Secure Hash Algorithm specified in 83.Tn FIPS 84160. 85It was quickly proven insecure, and has been superseded by 86.Tn SHA-1 . 87.Tn SHA-0 88is included for compatibility purposes only. 89.Pp 90The 91.Fn SHA1_Init , 92.Fn SHA1_Update , 93and 94.Fn SHA1_Final 95functions are the core functions. 96Allocate an 97.Vt SHA_CTX , 98initialize it with 99.Fn SHA1_Init , 100run over the data with 101.Fn SHA1_Update , 102and finally extract the result using 103.Fn SHA1_Final , 104which will also erase the 105.Vt SHA_CTX . 106.Pp 107.Fn SHA1_End 108is a wrapper for 109.Fn SHA1_Final 110which converts the return value to a 41-character 111(including the terminating '\e0') 112.Tn ASCII 113string which represents the 160 bits in hexadecimal. 114.Pp 115.Fn SHA1_File 116calculates the digest of a file, and uses 117.Fn SHA1_End 118to return the result. 119If the file cannot be opened, a null pointer is returned. 120.Fn SHA1_FileChunk 121is similar to 122.Fn SHA1_File , 123but it only calculates the digest over a byte-range of the file specified, 124starting at 125.Fa offset 126and spanning 127.Fa length 128bytes. 129If the 130.Fa length 131parameter is specified as 0, or more than the length of the remaining part 132of the file, 133.Fn SHA1_FileChunk 134calculates the digest from 135.Fa offset 136to the end of file. 137.Fn SHA1_Data 138calculates the digest of a chunk of data in memory, and uses 139.Fn SHA1_End 140to return the result. 141.Pp 142When using 143.Fn SHA1_End , 144.Fn SHA1_File , 145or 146.Fn SHA1_Data , 147the 148.Fa buf 149argument can be a null pointer, in which case the returned string 150is allocated with 151.Xr malloc 3 152and subsequently must be explicitly deallocated using 153.Xr free 3 154after use. 155If the 156.Fa buf 157argument is non-null it must point to at least 41 characters of buffer space. 158.Sh SEE ALSO 159.Xr md4 3 , 160.Xr md5 3 , 161.Xr ripemd 3 , 162.Xr sha256 3 , 163.Xr sha512 3 , 164.Xr skein 3 165.Sh HISTORY 166These functions appeared in 167.Fx 4.0 . 168.Sh AUTHORS 169The core hash routines were implemented by Eric Young based on the 170published 171.Tn FIPS 172standards. 173.Sh BUGS 174No method is known to exist which finds two files having the same hash value, 175nor to find a file with a specific hash value. 176There is on the other hand no guarantee that such a method does not exist. 177.Pp 178The 179.Tn IA32 180(Intel) implementation of 181.Tn SHA-1 182makes heavy use of the 183.Ql bswapl 184instruction, which is not present on the original 80386. 185Attempts to use 186.Tn SHA-1 187on those processors will cause an illegal instruction trap. 188(Arguably, the kernel should simply emulate this instruction.) 189