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MAN page from Trustix openssl-0.9.7m-1tr.i586.rpm

RSAUTL

Section: OpenSSL (1)
Updated: 2001-04-25
Index 

NAME

rsautl - RSA utility 

SYNOPSIS

openssl rsautl[-in file][-out file][-inkey file][-pubin][-certin][-sign][-verify][-encrypt][-decrypt][-pkcs][-ssl][-raw][-hexdump][-asn1parse] 

DESCRIPTION

The rsautl command can be used to sign, verify, encrypt and decryptdata using the RSA algorithm. 

COMMAND OPTIONS

-in filename
This specifies the input filename to read data from or standard inputif this option is not specified.
-out filename
specifies the output filename to write to or standard output bydefault.
-inkey file
the input key file, by default it should be an RSA private key.
-pubin
the input file is an RSA public key.
-certin
the input is a certificate containing an RSA public key.
-sign
sign the input data and output the signed result. This requiresand RSA private key.
-verify
verify the input data and output the recovered data.
-encrypt
encrypt the input data using an RSA public key.
-decrypt
decrypt the input data using an RSA private key.
-pkcs, -oaep, -ssl, -raw
the padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP,special padding used in SSL v2 backwards compatible handshakes,or no padding, respectively.For signatures, only -pkcs and -raw can be used.
-hexdump
hex dump the output data.
-asn1parse
asn1parse the output data, this is useful when combined with the-verify option.
 

NOTES

rsautl because it uses the RSA algorithm directly can only beused to sign or verify small pieces of data. 

EXAMPLES

Sign some data using a private key:

 openssl rsautl -sign -in file -inkey key.pem -out sig

Recover the signed data

 openssl rsautl -verify -in sig -inkey key.pem

Examine the raw signed data:

 openssl rsautl -verify -in file -inkey key.pem -raw -hexdump

 0000 - 00 01 ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................ 0010 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................ 0020 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................ 0030 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................ 0040 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................ 0050 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................ 0060 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................ 0070 - ff ff ff ff 00 68 65 6c-6c 6f 20 77 6f 72 6c 64   .....hello world

The PKCS#1 block formatting is evident from this. If this was done usingencrypt and decrypt the block would have been of type 2 (the second byte)and random padding data visible instead of the 0xff bytes.

It is possible to analyse the signature of certificates using thisutility in conjunction with asn1parse. Consider the self signedexample in certs/pca-cert.pem . Running asn1parse as follows yields:

 openssl asn1parse -in pca-cert.pem

    0:d=0  hl=4 l= 742 cons: SEQUENCE              4:d=1  hl=4 l= 591 cons:  SEQUENCE              8:d=2  hl=2 l=   3 cons:   cont [ 0 ]           10:d=3  hl=2 l=   1 prim:    INTEGER           :02   13:d=2  hl=2 l=   1 prim:   INTEGER           :00   16:d=2  hl=2 l=  13 cons:   SEQUENCE             18:d=3  hl=2 l=   9 prim:    OBJECT            :md5WithRSAEncryption   29:d=3  hl=2 l=   0 prim:    NULL                 31:d=2  hl=2 l=  92 cons:   SEQUENCE             33:d=3  hl=2 l=  11 cons:    SET                  35:d=4  hl=2 l=   9 cons:     SEQUENCE             37:d=5  hl=2 l=   3 prim:      OBJECT            :countryName   42:d=5  hl=2 l=   2 prim:      PRINTABLESTRING   :AU  ....  599:d=1  hl=2 l=  13 cons:  SEQUENCE            601:d=2  hl=2 l=   9 prim:   OBJECT            :md5WithRSAEncryption  612:d=2  hl=2 l=   0 prim:   NULL                614:d=1  hl=3 l= 129 prim:  BIT STRING

The final BIT STRING contains the actual signature. It can be extracted with:

 openssl asn1parse -in pca-cert.pem -out sig -noout -strparse 614

The certificate public key can be extracted with:

 openssl x509 -in test/testx509.pem -pubout -noout >pubkey.pem

The signature can be analysed with:

 openssl rsautl -in sig -verify -asn1parse -inkey pubkey.pem -pubin

    0:d=0  hl=2 l=  32 cons: SEQUENCE              2:d=1  hl=2 l=  12 cons:  SEQUENCE              4:d=2  hl=2 l=   8 prim:   OBJECT            :md5   14:d=2  hl=2 l=   0 prim:   NULL                 16:d=1  hl=2 l=  16 prim:  OCTET STRING            0000 - f3 46 9e aa 1a 4a 73 c9-37 ea 93 00 48 25 08 b5   .F...Js.7...H%..

This is the parsed version of an ASN1 DigestInfo structure. It can be seen thatthe digest used was md5. The actual part of the certificate that was signed canbe extracted with:

 openssl asn1parse -in pca-cert.pem -out tbs -noout -strparse 4

and its digest computed with:

 openssl md5 -c tbs MD5(tbs)= f3:46:9e:aa:1a:4a:73:c9:37:ea:93:00:48:25:08:b5

which it can be seen agrees with the recovered value above. 

SEE ALSO

dgst(1), rsa(1), genrsa(1)


 

Index

NAME
SYNOPSIS
DESCRIPTION
COMMAND OPTIONS
NOTES
EXAMPLES
SEE ALSO

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