rsautl

Langue: en

Autres versions - même langue

Version: 2007-09-17 (mandriva - 01/05/08)

Section: 1 (Commandes utilisateur)

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 decrypt data using the RSA algorithm.

COMMAND OPTIONS

-in filename
This specifies the input filename to read data from or standard input if this option is not specified.
-out filename
specifies the output filename to write to or standard output by default.
-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 requires and 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 be used 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 using encrypt 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 this utility in conjunction with asn1parse. Consider the self signed example 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 -pubkey -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 that the digest used was md5. The actual part of the certificate that was signed can be 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)