RSAUTL(1SSL)							      OpenSSL							      RSAUTL(1SSL)

NAME

       openssl-rsautl, rsautl - RSA utility

SYNOPSIS

       openssl rsautl [-help] [-in file] [-out file] [-inkey file] [-keyform PEM|DER|ENGINE] [-pubin] [-certin] [-sign] [-verify] [-encrypt]
       [-decrypt] [-rand file...]  [-writerand file] [-pkcs] [-ssl] [-raw] [-hexdump] [-asn1parse]

DESCRIPTION

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

OPTIONS

       -help
	   Print out a usage message.

       -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.

       -keyform PEM|DER|ENGINE
	   The key format PEM, DER or ENGINE.

       -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 an 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.

       -rand file...
	   A file or files containing random data used to seed the random number generator.  Multiple files can be specified separated by an OS-
	   dependent character.  The separator is ; for MS-Windows, , for OpenVMS, and : for all others.

       [-writerand file]
	   Writes random data to the specified file upon exit.	This can be used with a subsequent -rand flag.

       -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
	   Parse the ASN.1 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 sig -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)

COPYRIGHT

       Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in compliance with the License.  You can obtain a
       copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

1.1.1a								    2018-12-18							      RSAUTL(1SSL)