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)