SHA_Init
, SHA_Update
,
SHA_Final
, SHA_End
,
SHA_File
, SHA_FileChunk
,
SHA_Data
, SHA1_Init
,
SHA1_Update
, SHA1_Final
,
SHA1_End
, SHA1_File
,
SHA1_FileChunk
, SHA1_Data
—
calculate the FIPS 160 and 160-1 ``SHA'' message digests
Message Digest (MD4, MD5, etc.) Support Library (libmd,
-lmd)
#include <sys/types.h>
#include <sha.h>
void
SHA_Init
(SHA_CTX
*context);
void
SHA_Update
(SHA_CTX
*context, const unsigned
char *data, size_t
len);
void
SHA_Final
(unsigned
char digest[20], SHA_CTX
*context);
char *
SHA_End
(SHA_CTX
*context, char
*buf);
char *
SHA_File
(const
char *filename, char
*buf);
char *
SHA_FileChunk
(const
char *filename, char
*buf, off_t offset,
off_t length);
char *
SHA_Data
(const
unsigned char *data,
unsigned int len,
char *buf);
void
SHA1_Init
(SHA_CTX
*context);
void
SHA1_Update
(SHA_CTX
*context, const unsigned
char *data, size_t
len);
void
SHA1_Final
(unsigned
char digest[20], SHA_CTX
*context);
char *
SHA1_End
(SHA_CTX
*context, char
*buf);
char *
SHA1_File
(const
char *filename, char
*buf);
char *
SHA1_FileChunk
(const
char *filename, char
*buf, off_t offset,
off_t length);
char *
SHA1_Data
(const
unsigned char *data,
unsigned int len,
char *buf);
The SHA_
and SHA1_
functions
calculate a 160-bit cryptographic checksum (digest) for any number of input
bytes. A cryptographic checksum is a one-way hash function; that is, it is
computationally impractical to find the input corresponding to a particular
output. This net result is a “fingerprint” of the input-data,
which does not disclose the actual input.
SHA (or SHA-0) is the original Secure Hash Algorithm specified in
FIPS 160. It was quickly proven insecure, and has been superseded by SHA-1.
SHA-0 is included for compatibility purposes only.
The SHA1_Init
(),
SHA1_Update
(), and
SHA1_Final
() functions are the core functions.
Allocate an SHA_CTX, initialize it with
SHA1_Init
(), run over the data with
SHA1_Update
(), and finally extract the result using
SHA1_Final
(), which will also erase the
SHA_CTX.
SHA1_End
() is a wrapper for
SHA1_Final
() which converts the return value to a
41-character (including the terminating '\0') ASCII string which represents
the 160 bits in hexadecimal.
SHA1_File
() calculates the digest of a
file, and uses SHA1_End
() to return the result. If
the file cannot be opened, a null pointer is returned.
SHA1_FileChunk
() is similar to
SHA1_File
(), but it only calculates the digest over
a byte-range of the file specified, starting at offset
and spanning length bytes. If the
length parameter is specified as 0, or more than the
length of the remaining part of the file,
SHA1_FileChunk
() calculates the digest from
offset to the end of file.
SHA1_Data
() calculates the digest of a chunk of data
in memory, and uses SHA1_End
() to return the
result.
When using SHA1_End
(),
SHA1_File
(), or SHA1_Data
(),
the buf argument can be a null pointer, in which case
the returned string is allocated with
malloc(3)
and subsequently must be explicitly deallocated using
free(3)
after use. If the buf argument is non-null it must
point to at least 41 characters of buffer space.
The SHA1_End
() function called with a null buf argument
may fail and return NULL if:
- [
ENOMEM
]
- Insufficient storage space is available.
The SHA1_File
() and
SHA1_FileChunk
() may return NULL when underlying
open(2),
fstat(2),
lseek(2),
or
SHA1_End(2)
fail.
These functions appeared in FreeBSD 4.0.
The core hash routines were implemented by Eric Young based on the published
FIPS standards.
The SHA1 algorithm has been proven to be vulnerable to practical collision
attacks and should not be relied upon to produce unique outputs,
nor should it be used as part of a new cryptographic signature
scheme.
The IA32 (Intel) implementation of SHA-1 makes heavy use of the
‘bswapl
’ instruction, which is not
present on the original 80386. Attempts to use SHA-1 on those processors
will cause an illegal instruction trap. (Arguably, the kernel should simply
emulate this instruction.)