openssl-rsautl - RSA command
openssl rsautl [-help] [-in
file] [-passin arg] [-rev] [-out
file] [-inkey filename|uri] [-keyform
DER|PEM|P12|ENGINE] [-pubin]
[-certin] [-sign] [-verify] [-encrypt]
[-decrypt] [-pkcs] [-x931] [-oaep] [-raw]
[-hexdump] [-asn1parse] [-engine id]
[-rand files] [-writerand file]
[-provider name] [-provider-path path]
[-provparam [name:]key=value] [-propquery
propq]
This command has been deprecated. The openssl-pkeyutl(1)
command should be used instead.
This command can be used to sign, verify, encrypt and decrypt data
using the RSA algorithm.
- -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.
- -passin
arg
- The passphrase used in the output file. See see
openssl-passphrase-options(1).
- -rev
- Reverse the order of the input.
- -out
filename
- Specifies the output filename to write to or standard output by
default.
- -inkey
filename|uri
- The input key, by default it should be an RSA private key.
- -keyform
DER|PEM|P12|ENGINE
- The key format; unspecified by default. See
openssl-format-options(1) for details.
- -pubin
- By default a private key is read from the key input. With this option a
public key is read instead. If the input contains no public key but a
private key, its public part is used.
- -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.
- -pkcs, -oaep,
-x931, -raw
- The padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP, ANSI X9.31, or
no padding, respectively. For signatures, only -pkcs and
-raw can be used.
Note: because of protection against Bleichenbacher attacks,
decryption using PKCS#1 v1.5 mode will not return errors in case padding
check failed. Use -raw and inspect the returned value manually to
check if the padding is correct.
- -hexdump
- Hex dump the output data.
- -asn1parse
- Parse the ASN.1 output data, this is useful when combined with the
-verify option.
- -engine
id
- See "Engine Options" in openssl(1). This option is
deprecated.
- -rand files,
-writerand file
- See "Random State Options" in openssl(1) for
details.
- -provider
name
- -provider-path
path
- -provparam
[name:]key=value
- -propquery
propq
- See "Provider Options" in openssl(1), provider(7),
and property(7).
Since this command uses the RSA algorithm directly, it can only be
used to sign or verify small pieces of data.
Examples equivalent to these can be found in the documentation for
the non-deprecated openssl-pkeyutl(1) command.
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
command in conjunction with openssl-asn1parse(1). Consider the self
signed example in certs/pca-cert.pem. Running
openssl-asn1parse(1) 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.
openssl(1), openssl-pkeyutl(1),
openssl-dgst(1), openssl-rsa(1), openssl-genrsa(1)
This command was deprecated in OpenSSL 3.0.
The -engine option was deprecated in OpenSSL 3.0.
Copyright 2000-2023 The OpenSSL Project Authors. All Rights
Reserved.
Licensed under the Apache License 2.0 (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>.
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