28 The B<rsautl> command can be used to sign, verify, encrypt and decrypt
29 data using the RSA algorithm.
31 =head1 COMMAND OPTIONS
37 This specifies the input filename to read data from or standard input
38 if this option is not specified.
40 =item B<-out filename>
42 specifies the output filename to write to or standard output by
47 the input key file, by default it should be an RSA private key.
51 the input file is an RSA public key.
55 the input is a certificate containing an RSA public key.
59 sign the input data and output the signed result. This requires
64 verify the input data and output the recovered data.
68 encrypt the input data using an RSA public key.
72 decrypt the input data using an RSA private key.
74 =item B<-pkcs, -oaep, -ssl, -raw>
76 the padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP,
77 special padding used in SSL v2 backwards compatible handshakes,
78 or no padding, respectively.
79 For signatures, only B<-pkcs> and B<-raw> can be used.
83 hex dump the output data.
87 asn1parse the output data, this is useful when combined with the
94 B<rsautl> because it uses the RSA algorithm directly can only be
95 used to sign or verify small pieces of data.
99 Sign some data using a private key:
101 openssl rsautl -sign -in file -inkey key.pem -out sig
103 Recover the signed data
105 openssl rsautl -verify -in sig -inkey key.pem
107 Examine the raw signed data:
109 openssl rsautl -verify -in sig -inkey key.pem -raw -hexdump
111 0000 - 00 01 ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
112 0010 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
113 0020 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
114 0030 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
115 0040 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
116 0050 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
117 0060 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff ................
118 0070 - ff ff ff ff 00 68 65 6c-6c 6f 20 77 6f 72 6c 64 .....hello world
120 The PKCS#1 block formatting is evident from this. If this was done using
121 encrypt and decrypt the block would have been of type 2 (the second byte)
122 and random padding data visible instead of the 0xff bytes.
124 It is possible to analyse the signature of certificates using this
125 utility in conjunction with B<asn1parse>. Consider the self signed
126 example in certs/pca-cert.pem . Running B<asn1parse> as follows yields:
128 openssl asn1parse -in pca-cert.pem
130 0:d=0 hl=4 l= 742 cons: SEQUENCE
131 4:d=1 hl=4 l= 591 cons: SEQUENCE
132 8:d=2 hl=2 l= 3 cons: cont [ 0 ]
133 10:d=3 hl=2 l= 1 prim: INTEGER :02
134 13:d=2 hl=2 l= 1 prim: INTEGER :00
135 16:d=2 hl=2 l= 13 cons: SEQUENCE
136 18:d=3 hl=2 l= 9 prim: OBJECT :md5WithRSAEncryption
137 29:d=3 hl=2 l= 0 prim: NULL
138 31:d=2 hl=2 l= 92 cons: SEQUENCE
139 33:d=3 hl=2 l= 11 cons: SET
140 35:d=4 hl=2 l= 9 cons: SEQUENCE
141 37:d=5 hl=2 l= 3 prim: OBJECT :countryName
142 42:d=5 hl=2 l= 2 prim: PRINTABLESTRING :AU
144 599:d=1 hl=2 l= 13 cons: SEQUENCE
145 601:d=2 hl=2 l= 9 prim: OBJECT :md5WithRSAEncryption
146 612:d=2 hl=2 l= 0 prim: NULL
147 614:d=1 hl=3 l= 129 prim: BIT STRING
150 The final BIT STRING contains the actual signature. It can be extracted with:
152 openssl asn1parse -in pca-cert.pem -out sig -noout -strparse 614
154 The certificate public key can be extracted with:
156 openssl x509 -in test/testx509.pem -pubkey -noout >pubkey.pem
158 The signature can be analysed with:
160 openssl rsautl -in sig -verify -asn1parse -inkey pubkey.pem -pubin
162 0:d=0 hl=2 l= 32 cons: SEQUENCE
163 2:d=1 hl=2 l= 12 cons: SEQUENCE
164 4:d=2 hl=2 l= 8 prim: OBJECT :md5
165 14:d=2 hl=2 l= 0 prim: NULL
166 16:d=1 hl=2 l= 16 prim: OCTET STRING
167 0000 - f3 46 9e aa 1a 4a 73 c9-37 ea 93 00 48 25 08 b5 .F...Js.7...H%..
169 This is the parsed version of an ASN1 DigestInfo structure. It can be seen that
170 the digest used was md5. The actual part of the certificate that was signed can
173 openssl asn1parse -in pca-cert.pem -out tbs -noout -strparse 4
175 and its digest computed with:
178 MD5(tbs)= f3:46:9e:aa:1a:4a:73:c9:37:ea:93:00:48:25:08:b5
180 which it can be seen agrees with the recovered value above.
184 L<dgst(1)|dgst(1)>, L<rsa(1)|rsa(1)>, L<genrsa(1)|genrsa(1)>