rsautl.pod revision 325337 
1=pod
2
3=head1 NAME
4
5openssl-rsautl,
6rsautl - RSA utility
7
8=head1 SYNOPSIS
9
10B<openssl> B<rsautl>
11[B<-in file>]
12[B<-out file>]
13[B<-inkey file>]
14[B<-pubin>]
15[B<-certin>]
16[B<-sign>]
17[B<-verify>]
18[B<-encrypt>]
19[B<-decrypt>]
20[B<-pkcs>]
21[B<-ssl>]
22[B<-raw>]
23[B<-hexdump>]
24[B<-asn1parse>]
25
26=head1 DESCRIPTION
27
28The B<rsautl> command can be used to sign, verify, encrypt and decrypt
29data using the RSA algorithm.
30
31=head1 COMMAND OPTIONS
32
33=over 4
34
35=item B<-in filename>
36
37This specifies the input filename to read data from or standard input
38if this option is not specified.
39
40=item B<-out filename>
41
42specifies the output filename to write to or standard output by
43default.
44
45=item B<-inkey file>
46
47the input key file, by default it should be an RSA private key.
48
49=item B<-pubin>
50
51the input file is an RSA public key. 
52
53=item B<-certin>
54
55the input is a certificate containing an RSA public key. 
56
57=item B<-sign>
58
59sign the input data and output the signed result. This requires
60and RSA private key.
61
62=item B<-verify>
63
64verify the input data and output the recovered data.
65
66=item B<-encrypt>
67
68encrypt the input data using an RSA public key.
69
70=item B<-decrypt>
71
72decrypt the input data using an RSA private key.
73
74=item B<-pkcs, -oaep, -ssl, -raw>
75
76the padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP,
77special padding used in SSL v2 backwards compatible handshakes,
78or no padding, respectively.
79For signatures, only B<-pkcs> and B<-raw> can be used.
80
81=item B<-hexdump>
82
83hex dump the output data.
84
85=item B<-asn1parse>
86
87asn1parse the output data, this is useful when combined with the
88B<-verify> option.
89
90=back
91
92=head1 NOTES
93
94B<rsautl> because it uses the RSA algorithm directly can only be
95used to sign or verify small pieces of data.
96
97=head1 EXAMPLES
98
99Sign some data using a private key:
100
101 openssl rsautl -sign -in file -inkey key.pem -out sig
102
103Recover the signed data
104
105 openssl rsautl -verify -in sig -inkey key.pem
106
107Examine the raw signed data:
108
109 openssl rsautl -verify -in sig -inkey key.pem -raw -hexdump
110
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
119
120The PKCS#1 block formatting is evident from this. If this was done using
121encrypt and decrypt the block would have been of type 2 (the second byte)
122and random padding data visible instead of the 0xff bytes.
123
124It is possible to analyse the signature of certificates using this
125utility in conjunction with B<asn1parse>. Consider the self signed
126example in certs/pca-cert.pem . Running B<asn1parse> as follows yields:
127
128 openssl asn1parse -in pca-cert.pem
129
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
143  ....
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        
148
149
150The final BIT STRING contains the actual signature. It can be extracted with:
151
152 openssl asn1parse -in pca-cert.pem -out sig -noout -strparse 614
153
154The certificate public key can be extracted with:
155 
156 openssl x509 -in test/testx509.pem -pubkey -noout >pubkey.pem
157
158The signature can be analysed with:
159
160 openssl rsautl -in sig -verify -asn1parse -inkey pubkey.pem -pubin
161
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%..
168
169This is the parsed version of an ASN1 DigestInfo structure. It can be seen that
170the digest used was md5. The actual part of the certificate that was signed can
171be extracted with:
172
173 openssl asn1parse -in pca-cert.pem -out tbs -noout -strparse 4
174
175and its digest computed with:
176
177 openssl md5 -c tbs
178 MD5(tbs)= f3:46:9e:aa:1a:4a:73:c9:37:ea:93:00:48:25:08:b5
179
180which it can be seen agrees with the recovered value above.
181
182=head1 SEE ALSO
183
184L<dgst(1)|dgst(1)>, L<rsa(1)|rsa(1)>, L<genrsa(1)|genrsa(1)>
185