sbin/md5/md5.1

.Dd May 10, 2023
.Dt MD5 1
.Os
.Sh NAME
.Nm md5 , sha1 , sha224 , sha256 , sha384 ,
.Nm sha512 , sha512t224 , sha512t256 ,
.Nm rmd160 , skein256 , skein512 , skein1024 ,
.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum ,
.Nm sha512sum , sha512t224sum , sha512t256sum ,
.Nm rmd160sum , skein256sum , skein512sum , skein1024sum ,
.Nm shasum
.Nd calculate a message-digest fingerprint (checksum) for a file
.Sh SYNOPSIS
.Nm
.Op Fl pqrtx
.Op Fl c Ar string
.Op Fl s Ar string
.Op Ar
.Pp
.Nm md5sum
.Op Fl bctwz
.Op Fl -binary
.Op Fl -check
.Op Fl -help
.Op Fl -ignore-missing
.Op Fl -quiet
.Op Fl -status
.Op Fl -strict
.Op Fl -tag
.Op Fl -text
.Op Fl -version
.Op Fl -warn
.Op Fl -zero
.Op Ar
.Pp
(All other hashes have the same options and usage.)
.Pp
.Nm shasum
.Op Fl 0bchqstUvw
.Op Fl -01
.Op Fl a | -algorithm Ar alg
.Op Fl -binary
.Op Fl -check
.Op Fl -help
.Op Fl -ignore-missing
.Op Fl -quiet
.Op Fl -status
.Op Fl -strict
.Op Fl -tag
.Op Fl -text
.Op Fl -UNIVERSAL
.Op Fl -version
.Op Fl -warn
.Op Ar
.Sh DESCRIPTION
The
.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 , sha512t224 , sha512t256 ,
.Nm rmd160 , skein256 , skein512 ,
and
.Nm skein1024
utilities take as input a message of arbitrary length and produce as
output a
.Dq fingerprint
or
.Dq message digest
of the input.
.Pp
The
.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum , sha512sum ,
.Nm sha512t224sum , sha512t256sum , rmd160sum , skein256sum , skein512sum ,
and
.Nm skein1024sum
utilities do the same, but with command-line options and an output
format that match those of their similary named GNU utilities.
.Pp
The
.Nm shasum
utility does the same, but with command-line options and an output
format that match those of the similarly named utility that ships with
Perl.
.Pp
It is conjectured that it is computationally infeasible to
produce two messages having the same message digest, or to produce any
message having a given prespecified target message digest.
The SHA-224 , SHA-256 , SHA-384 , SHA-512, RIPEMD-160,
and SKEIN
algorithms are intended for digital signature applications, where a
large file must be
.Dq compressed
in a secure manner before being encrypted with a private
(secret)
key under a public-key cryptosystem such as RSA.
.Pp
The MD5 and SHA-1 algorithms have been proven to be vulnerable to practical
collision attacks and should not be relied upon to produce unique outputs,
.Em nor should they be used as part of a cryptographic signature scheme.
As of 2017-03-02, there is no publicly known method to
.Em reverse
either algorithm, i.e., to find an input that produces a specific
output.
.Pp
SHA-512t256 is a version of SHA-512 truncated to only 256 bits.
On 64-bit hardware, this algorithm is approximately 50% faster than SHA-256 but
with the same level of security.
The hashes are not interchangeable.
.Pp
SHA-512t224 is identical to SHA-512t256, but with the digest truncated
to 224 bits.
.Pp
It is recommended that all new applications use SHA-512 or SKEIN-512
instead of one of the other hash functions.
.Ss BSD OPTIONS
The following options are available in BSD mode, i.e. when the program
is invoked with a name that does not end in
.Dq sum :
.Bl -tag -width indent
.It Fl c Ar string , Fl -check= Ns Ar string
Compare the digest of the file against this string.
If combined with the
.Fl q
or
.Fl -quiet
option, the calculated digest is printed in addition to the exit status being set.
.Pq Note that this option is not yet useful if multiple files are specified.
.It Fl p , -passthrough
Echo stdin to stdout and append the checksum to stdout.
.It Fl q , -quiet
Quiet mode \(em only the checksum is printed out.
Overrides the
.Fl r
or
.Fl -reverse
option.
.It Fl r , -reverse
Reverses the format of the output.
This helps with visual diffs.
Does nothing
when combined with the
.Fl ptx
options.
.It Fl s Ar string , Fl -string= Ns Ar string
Print a checksum of the given
.Ar string .
.It Fl t , Fl -time-trial
Run a built-in time trial.
For the
.Nm -sum
versions, this is a nop for compatibility with coreutils.
.It Fl x , Fl -self-test
Run a built-in test script.
.El
.Ss GNU OPTIONS
The following options are available in GNU mode, i.e. when the program
is invoked with a name that ends in
.Dq sum :
.Bl -tag -width indent
.It Fl b , Fl -binary
Read files in binary mode.
.It Fl c , Fl -check
The file passed as arguments must contain digest lines generated by the same
digest algorithm in either classical BSD format or in GNU coreutils format.
A line with the file name followed by a colon
.Dq ":"
and either OK or FAILED is written for each well-formed line in the digest file.
If applicable, the number of failed comparisons and the number of lines that were
skipped since they were not well-formed are printed at the end.
The
.Fl -quiet
option can be used to quiesce the output unless there are mismatched entries in
the digest.
.It Fl -help
Print a usage message and exit.
.It Fl -ignore-missing
When verifying checksums, ignore files for which checksums are given
but which aren't found on disk.
.It Fl -quiet
When verifying checksums, do not print anything unless the
verification fails.
.It Fl -status
When verifying checksums, do not print anything at all.
The exit code will reflect whether verification succeeded.
.It Fl -strict
When verifying checksums, fail if the input is malformed.
.It Fl -tag
Produce BSD-style output.
.It Fl t , Fl -text
Read files in text mode.
This is the default.
Note that this implementation does not differentiate between binary
and text mode.
.It Fl -version
Print version information and exit.
.It Fl w , Fl -warn
When verifying checksums, warn about malformed input.
.It Fl z , Fl -zero
Terminate output lines with NUL rather than with newline.
.El
.Ss PERL OPTIONS
The following options are available in Perl mode, i.e. when the program
is invoked with the name
.Dq shasum :
.Bl -tag -width indent
.It Fl 0 , Fl -01
Read files in bits mode: ASCII
.Sq 0
and
.Sq 1
characters correspond to 0 and 1 bits, respectively, and all other
characters are ignored.
See
.Sx BUGS .
.It Fl a Ar alg , Fl -algorithm Ar alg
Use the specified algorithm:
.Dq 1
for SHA-1 (default),
.Dq xxx
for
.Va xxx Ns -bit
SHA-2 (e.g.
.Dq 256
for SHA-256)
or
.Dq xxxyyy
for
.Va xxx Ns -bit
SHA-2 truncated to
.Va yyy
bits (e.g.
.Dq 512224
for SHA-512/224).
.It Fl b , Fl -binary
Read files in binary mode.
.It Fl c , Fl -check
The file passed as arguments must contain digest lines generated by the same
digest algorithm in either classical BSD format or in GNU coreutils format.
A line with the file name followed by a colon
.Dq ":"
and either OK or FAILED is written for each well-formed line in the digest file.
If applicable, the number of failed comparisons and the number of lines that were
skipped since they were not well-formed are printed at the end.
The
.Fl -quiet
option can be used to quiesce the output unless there are mismatched entries in
the digest.
.It Fl -help
Print a usage message and exit.
.It Fl -ignore-missing
When verifying checksums, ignore files for which checksums are given
but which aren't found on disk.
.It Fl -quiet
When verifying checksums, do not print anything unless the
verification fails.
.It Fl -status
When verifying checksums, do not print anything at all.
The exit code will reflect whether verification succeeded.
.It Fl -strict
When verifying checksums, fail if the input is malformed.
.It Fl -tag
Produce BSD-style output.
.It Fl t , Fl -text
Read files in text mode.
This is the default.
Note that this implementation does not differentiate between binary
and text mode.
.It Fl U , Fl -UNIVERSAL
Read files in universal mode: any CR-LF pair, as well as any CR not
followed by LF, is translated to LF before the digest is computed.
.It Fl -version
Print version information and exit.
.It Fl w , Fl -warn
When verifying checksums, warn about malformed input.
.El
.Sh EXIT STATUS
The
.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 ,
.Nm sha512t224 , sha512t256 ,
.Nm rmd160 , skein256 , skein512 ,
and
.Nm skein1024
utilities exit 0 on success,
1 if at least one of the input files could not be read,
and 2 if at least one file does not have the same hash as the
.Fl c
option.
.Pp
The
.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum , sha512sum ,
.Nm sha512t224sum , sha512t256sum ,
.Nm rmd160 , skein256 , skein512 , skein1024
and
.Nm shasum
utilities exit 0 on success and 1 if at least one of the input files
could not be read or, when verifying checksums, does not have the
expected checksum.
.Sh EXAMPLES
Calculate the MD5 checksum of the string
.Dq Hello .
.Bd -literal -offset indent
$ md5 -s Hello
MD5 ("Hello") = 8b1a9953c4611296a827abf8c47804d7
.Ed
.Pp
Same as above, but note the absence of the newline character in the input
string:
.Bd -literal -offset indent
$ echo -n Hello | md5
8b1a9953c4611296a827abf8c47804d7
.Ed
.Pp
Calculate the checksum of multiple files reversing the output:
.Bd -literal -offset indent
$ md5 -r /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6 /boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd /etc/rc.conf
.Ed
.Pp
This is almost but not quite identical to the output from GNU mode:
.Bd -literal -offset indent
$ md5sum /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6  /boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd  /etc/rc.conf
.Ed
.Pp
Note the two spaces between hash and file name.
If binary mode is requested, they are instead separated by a space and
an asterisk:
.Bd -literal -offset indent
$ md5sum -b /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6 */boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd */etc/rc.conf
.Ed
.Pp
Write the digest for
.Pa /boot/loader.conf
in a file named
.Pa digest .
Then calculate the checksum again and validate it against the checksum string
extracted from the
.Pa digest
file:
.Bd -literal -offset indent
$ md5 /boot/loader.conf > digest && md5 -c $(cut -f2 -d= digest) /boot/loader.conf
MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6
.Ed
.Pp
Same as above but comparing the digest against an invalid string
.Pq Dq randomstring ,
which results in a failure.
.Bd -literal -offset indent
$ md5 -c randomstring /boot/loader.conf
MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6 [ Failed ]
.Ed
.Pp
In GNU mode, the
.Fl c
option does not compare against a hash string passed as parameter.
Instead, it expects a digest file, as created under the name
.Pa digest
for
.Pa /boot/loader.conf
in the example above.
.Bd -literal -offset indent
$ md5 -c digest /boot/loader.conf
/boot/loader.conf: OK
.Ed
.Pp
The digest file may contain any number of lines in the format
generated in either BSD or GNU mode.
If a hash value does not match the file,
.Dq FAILED
is printed instead of
.Dq OK .
.Sh SEE ALSO
.Xr cksum 1 ,
.Xr md5 3 ,
.Xr ripemd 3 ,
.Xr sha 3 ,
.Xr sha256 3 ,
.Xr sha384 3 ,
.Xr sha512 3 ,
.Xr skein 3
.Rs
.%A R. Rivest
.%T The MD5 Message-Digest Algorithm
.%O RFC1321
.Re
.Rs
.%A J. Burrows
.%T The Secure Hash Standard
.%O FIPS PUB 180-2
.Re
.Rs
.%A D. Eastlake and P. Jones
.%T US Secure Hash Algorithm 1
.%O RFC 3174
.Re
.Pp
RIPEMD-160 is part of the ISO draft standard
.Qq ISO/IEC DIS 10118-3
on dedicated hash functions.
.Pp
Secure Hash Standard (SHS):
.Pa https://www.nist.gov/publications/secure-hash-standard-shs
.Pp
The RIPEMD-160 page:
.Pa https://homes.esat.kuleuven.be/~bosselae/ripemd160.html
.Sh BUGS
In bits mode, the original
.Nm shasum
script is capable of processing inputs of arbitrary length.
This implementation is not, and will issue an error if the input
length is not a multiple of eight bits.
.Sh ACKNOWLEDGMENTS
.An -nosplit
This utility was originally derived from a program which was placed in
the public domain for free general use by RSA Data Security.
.Pp
Support for SHA-1 and RIPEMD-160 was added by
.An Oliver Eikemeier Aq Mt eik@FreeBSD.org .
.Pp
Support for SHA-2 was added by
.An Colin Percival Aq Mt cperciva@FreeBSD.org
and
.An Allan Jude Aq Mt allanjude@FreeBSD.org .
.Pp
Support for SKEIN was added by
.An Allan Jude Aq Mt allanjude@FreeBSD.org .
.Pp
Compatibility with GNU coreutils was added by
.An Warner Losh Aq Mt imp@FreeBSD.org
and much expanded by
.An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org ,
who also added Perl compatibility.