183 lines
5 KiB
Text
183 lines
5 KiB
Text
=pod
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=head1 NAME
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rsautl - RSA utility
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=head1 SYNOPSIS
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B<openssl> B<rsautl>
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[B<-in file>]
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[B<-out file>]
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[B<-inkey file>]
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[B<-pubin>]
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[B<-certin>]
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[B<-sign>]
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[B<-verify>]
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[B<-encrypt>]
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[B<-decrypt>]
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[B<-pkcs>]
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[B<-ssl>]
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[B<-raw>]
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[B<-hexdump>]
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[B<-asn1parse>]
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=head1 DESCRIPTION
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The B<rsautl> command can be used to sign, verify, encrypt and decrypt
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data using the RSA algorithm.
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=head1 COMMAND OPTIONS
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=over 4
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=item B<-in filename>
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This specifies the input filename to read data from or standard input
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if this option is not specified.
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=item B<-out filename>
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specifies the output filename to write to or standard output by
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default.
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=item B<-inkey file>
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the input key file, by default it should be an RSA private key.
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=item B<-pubin>
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the input file is an RSA public key.
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=item B<-certin>
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the input is a certificate containing an RSA public key.
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=item B<-sign>
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sign the input data and output the signed result. This requires
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and RSA private key.
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=item B<-verify>
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verify the input data and output the recovered data.
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=item B<-encrypt>
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encrypt the input data using an RSA public key.
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=item B<-decrypt>
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decrypt the input data using an RSA private key.
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=item B<-pkcs, -oaep, -ssl, -raw>
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the padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP,
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special padding used in SSL v2 backwards compatible handshakes,
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or no padding, respectively.
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For signatures, only B<-pkcs> and B<-raw> can be used.
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=item B<-hexdump>
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hex dump the output data.
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=item B<-asn1parse>
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asn1parse the output data, this is useful when combined with the
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B<-verify> option.
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=back
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=head1 NOTES
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B<rsautl> because it uses the RSA algorithm directly can only be
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used to sign or verify small pieces of data.
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=head1 EXAMPLES
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Sign some data using a private key:
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openssl rsautl -sign -in file -inkey key.pem -out sig
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Recover the signed data
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openssl rsautl -sign -in sig -inkey key.pem
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Examine the raw signed data:
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openssl rsautl -sign -in file -inkey key.pem -raw -hexdump
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0000 - 00 01 ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
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0010 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
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0020 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
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0030 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
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0040 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
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0050 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
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0060 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
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0070 - ff ff ff ff 00 68 65 6c-6c 6f 20 77 6f 72 6c 64 .....hello world
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The PKCS#1 block formatting is evident from this. If this was done using
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encrypt and decrypt the block would have been of type 2 (the second byte)
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and random padding data visible instead of the 0xff bytes.
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It is possible to analyse the signature of certificates using this
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utility in conjunction with B<asn1parse>. Consider the self signed
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example in certs/pca-cert.pem . Running B<asn1parse> as follows yields:
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openssl asn1parse -in pca-cert.pem
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0:d=0 hl=4 l= 742 cons: SEQUENCE
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4:d=1 hl=4 l= 591 cons: SEQUENCE
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8:d=2 hl=2 l= 3 cons: cont [ 0 ]
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10:d=3 hl=2 l= 1 prim: INTEGER :02
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13:d=2 hl=2 l= 1 prim: INTEGER :00
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16:d=2 hl=2 l= 13 cons: SEQUENCE
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18:d=3 hl=2 l= 9 prim: OBJECT :md5WithRSAEncryption
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29:d=3 hl=2 l= 0 prim: NULL
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31:d=2 hl=2 l= 92 cons: SEQUENCE
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33:d=3 hl=2 l= 11 cons: SET
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35:d=4 hl=2 l= 9 cons: SEQUENCE
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37:d=5 hl=2 l= 3 prim: OBJECT :countryName
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42:d=5 hl=2 l= 2 prim: PRINTABLESTRING :AU
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....
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599:d=1 hl=2 l= 13 cons: SEQUENCE
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601:d=2 hl=2 l= 9 prim: OBJECT :md5WithRSAEncryption
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612:d=2 hl=2 l= 0 prim: NULL
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614:d=1 hl=3 l= 129 prim: BIT STRING
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The final BIT STRING contains the actual signature. It can be extracted with:
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openssl asn1parse -in pca-cert.pem -out sig -noout -strparse 614
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The certificate public key can be extracted with:
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openssl x509 -in test/testx509.pem -pubout -noout >pubkey.pem
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The signature can be analysed with:
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openssl rsautl -in sig -verify -asn1parse -inkey pubkey.pem -pubin
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0:d=0 hl=2 l= 32 cons: SEQUENCE
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2:d=1 hl=2 l= 12 cons: SEQUENCE
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4:d=2 hl=2 l= 8 prim: OBJECT :md5
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14:d=2 hl=2 l= 0 prim: NULL
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16:d=1 hl=2 l= 16 prim: OCTET STRING
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0000 - f3 46 9e aa 1a 4a 73 c9-37 ea 93 00 48 25 08 b5 .F...Js.7...H%..
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This is the parsed version of an ASN1 DigestInfo structure. It can be seen that
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the digest used was md5. The actual part of the certificate that was signed can
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be extracted with:
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openssl asn1parse -in pca-cert.pem -out tbs -noout -strparse 4
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and its digest computed with:
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openssl md5 -c tbs
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MD5(tbs)= f3:46:9e:aa:1a:4a:73:c9:37:ea:93:00:48:25:08:b5
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which it can be seen agrees with the recovered value above.
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=head1 SEE ALSO
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L<dgst(1)|dgst(1)>, L<rsa(1)|rsa(1)>, L<genrsa(1)|genrsa(1)>
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