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7fc67e0a33
The RSA decryption as implemented before required very careful handling of both the exit code returned by OpenSSL and the potentially returned ciphertext. Looking at the recent security vulnerabilities (CVE-2020-25659 and CVE-2020-25657) it is unlikely that most users of OpenSSL do it correctly. Given that correct code requires side channel secure programming in application code, we can classify the existing RSA decryption methods as CWE-676, which in turn likely causes CWE-208 and CWE-385 in application code. To prevent that, we can use a technique called "implicit rejection". For that we generate a random message to be returned in case the padding check fails. We generate the message based on static secret data (the private exponent) and the provided ciphertext (so that the attacker cannot determine that the returned value is randomly generated instead of result of decryption and de-padding). We return it in case any part of padding check fails. The upshot of this approach is that then not only is the length of the returned message useless as the Bleichenbacher oracle, so are the actual bytes of the returned message. So application code doesn't have to perform any operations on the returned message in side-channel free way to remain secure against Bleichenbacher attacks. Note: this patch implements a specific algorithm, shared with Mozilla NSS, so that the attacker cannot use one library as an oracle against the other in heterogeneous environments. Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com> Reviewed-by: Tim Hudson <tjh@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.org> (Merged from https://github.com/openssl/openssl/pull/13817)
248 lines
6.5 KiB
Plaintext
248 lines
6.5 KiB
Plaintext
=pod
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{- OpenSSL::safe::output_do_not_edit_headers(); -}
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=head1 NAME
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openssl-rsautl - RSA command
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=head1 SYNOPSIS
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B<openssl> B<rsautl>
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[B<-help>]
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[B<-in> I<file>]
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[B<-passin> I<arg>]
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[B<-rev>]
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[B<-out> I<file>]
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[B<-inkey> I<filename>|I<uri>]
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[B<-keyform> B<DER>|B<PEM>|B<P12>|B<ENGINE>]
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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<-x931>]
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[B<-oaep>]
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[B<-raw>]
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[B<-hexdump>]
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[B<-asn1parse>]
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{- $OpenSSL::safe::opt_engine_synopsis -}{- $OpenSSL::safe::opt_r_synopsis -}
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{- $OpenSSL::safe::opt_provider_synopsis -}
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=head1 DESCRIPTION
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This command has been deprecated.
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The L<openssl-pkeyutl(1)> command should be used instead.
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This command can be used to sign, verify, encrypt and decrypt
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data using the RSA algorithm.
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=head1 OPTIONS
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=over 4
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=item B<-help>
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Print out a usage message.
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=item B<-in> I<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<-passin> I<arg>
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The passphrase used in the output file.
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See see L<openssl-passphrase-options(1)>.
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=item B<-rev>
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Reverse the order of the input.
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=item B<-out> I<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> I<filename>|I<uri>
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The input key, by default it should be an RSA private key.
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=item B<-keyform> B<DER>|B<PEM>|B<P12>|B<ENGINE>
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The key format; unspecified by default.
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See L<openssl-format-options(1)> for details.
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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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an 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>, B<-oaep>, B<-x931> B<-raw>
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The padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP,
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ANSI X9.31, or no padding, respectively.
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For signatures, only B<-pkcs> and B<-raw> can be used.
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Note: because of protection against Bleichenbacher attacks, decryption
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using PKCS#1 v1.5 mode will not return errors in case padding check failed.
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Use B<-raw> and inspect the returned value manually to check if the
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padding is correct.
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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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Parse the ASN.1 output data, this is useful when combined with the
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B<-verify> option.
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{- $OpenSSL::safe::opt_engine_item -}
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{- $OpenSSL::safe::opt_r_item -}
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{- $OpenSSL::safe::opt_provider_item -}
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=back
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=head1 NOTES
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Since this command uses the RSA algorithm directly, it 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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Examples equivalent to these can be found in the documentation for the
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non-deprecated L<openssl-pkeyutl(1)> command.
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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 -verify -in sig -inkey key.pem
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Examine the raw signed data:
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openssl rsautl -verify -in sig -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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command in conjunction with L<openssl-asn1parse(1)>. Consider the self signed
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example in F<certs/pca-cert.pem>. Running L<openssl-asn1parse(1)> as follows
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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 -pubkey -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<openssl(1)>,
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L<openssl-pkeyutl(1)>,
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L<openssl-dgst(1)>,
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L<openssl-rsa(1)>,
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L<openssl-genrsa(1)>
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=head1 HISTORY
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This command was deprecated in OpenSSL 3.0.
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The B<-engine> option was deprecated in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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