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rsautl(1ssl)


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)



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