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 February 25, 1999 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 . 104.Pp 105.Fn SHA1_End 106is a wrapper for 107.Fn SHA1_Final 108which converts the return value to a 41-character 109(including the terminating '\e0') 110.Tn ASCII 111string which represents the 160 bits in hexadecimal. 112.Pp 113.Fn SHA1_File 114calculates the digest of a file, and uses 115.Fn SHA1_End 116to return the result. 117If the file cannot be opened, a null pointer is returned. 118.Fn SHA1_FileChunk 119is similar to 120.Fn SHA1_File , 121but it only calculates the digest over a byte-range of the file specified, 122starting at 123.Fa offset 124and spanning 125.Fa length 126bytes. 127If the 128.Fa length 129parameter is specified as 0, or more than the length of the remaining part 130of the file, 131.Fn SHA1_FileChunk 132calculates the digest from 133.Fa offset 134to the end of file. 135.Fn SHA1_Data 136calculates the digest of a chunk of data in memory, and uses 137.Fn SHA1_End 138to return the result. 139.Pp 140When using 141.Fn SHA1_End , 142.Fn SHA1_File , 143or 144.Fn SHA1_Data , 145the 146.Fa buf 147argument can be a null pointer, in which case the returned string 148is allocated with 149.Xr malloc 3 150and subsequently must be explicitly deallocated using 151.Xr free 3 152after use. 153If the 154.Fa buf 155argument is non-null it must point to at least 41 characters of buffer space. 156.Sh SEE ALSO 157.Xr md2 3 , 158.Xr md4 3 , 159.Xr md5 3 , 160.Xr ripemd 3 , 161.Xr sha256 3 162.Sh HISTORY 163These functions appeared in 164.Fx 4.0 . 165.Sh AUTHORS 166The core hash routines were implemented by Eric Young based on the 167published 168.Tn FIPS 169standards. 170.Sh BUGS 171No method is known to exist which finds two files having the same hash value, 172nor to find a file with a specific hash value. 173There is on the other hand no guarantee that such a method does not exist. 174.Pp 175The 176.Tn IA32 177(Intel) implementation of 178.Tn SHA-1 179makes heavy use of the 180.Ql bswapl 181instruction, which is not present on the original 80386. 182Attempts to use 183.Tn SHA-1 184on those processors will cause an illegal instruction trap. 185(Arguably, the kernel should simply emulate this instruction.) 186