27b138e9db
spelling: algorithm spelling: anyway spelling: assigned spelling: authenticated spelling: callback spelling: certificate spelling: compatibility spelling: configuration spelling: digest spelling: encrypted spelling: function spelling: output spelling: receive spelling: renegotiation spelling: signing spelling: similar spelling: string (Merged from https://github.com/openssl/openssl/pull/3580)Reviewed-by: Rich Salz <rsalz@openssl.org> Reviewed-by: Kurt Roeckx <kurt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/3580)
111 lines
4.2 KiB
Text
111 lines
4.2 KiB
Text
=pod
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=head1 NAME
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RSA-PSS - EVP_PKEY RSA-PSS algorithm support
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=head1 SYNOPSIS
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#include <openssl/rsa.h>
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int EVP_PKEY_CTX_set_rsa_pss_keygen_md(EVP_PKEY_CTX *pctx,
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const EVP_MD *md);
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int EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md(EVP_PKEY_CTX *pctx,
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const EVP_MD *md);
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int EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen(EVP_PKEY_CTX *pctx,
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int saltlen);
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=head1 DESCRIPTION
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The B<RSA-PSS> EVP_PKEY implementation is a restricted version of the RSA
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algorithm which only supports signing, verification and key generation
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using PSS padding modes with optional parameter restrictions.
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It has associated private key and public key formats.
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This algorithm shares several control operations with the B<RSA> algorithm
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but with some restrictions described below.
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=head1 SIGNING AND VERIFICATION
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Signing and verification is similar to the B<RSA> algorithm except the
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padding mode is always PSS. If the key in use has parameter restrictions then
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the corresponding signature parameters are set to the restrictions:
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for example, if the key can only be used with digest SHA256, MGF1 SHA256
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and minimum salt length 32 then the digest, MGF1 digest and salt length
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will be set to SHA256, SHA256 and 32 respectively.
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The macro EVP_PKEY_CTX_set_rsa_padding() is supported but an error is
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returned if an attempt is made to set the padding mode to anything other
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than B<PSS>. It is otherwise similar to the B<RSA> version.
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The EVP_PKEY_CTX_set_rsa_pss_saltlen() macro is used to set the salt length.
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If the key has usage restrictions then an error is returned if an attempt is
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made to set the salt length below the minimum value. It is otherwise similar
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to the B<RSA> operation except detection of the salt length (using
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RSA_PSS_SALTLEN_AUTO is not supported for verification if the key has
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usage restrictions.
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The EVP_PKEY_CTX_set_signature_md() and EVP_PKEY_CTX_set_rsa_mgf1_md() macros
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are used to set the digest and MGF1 algorithms respectively. If the key has
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usage restrictions then an error is returned if an attempt is made to set the
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digest to anything other than the restricted value. Otherwise these are
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similar to the B<RSA> versions.
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=head1 KEY GENERATION
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As with RSA key generation the EVP_PKEY_CTX_set_rsa_rsa_keygen_bits()
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and EVP_PKEY_CTX_set_rsa_keygen_pubexp() macros are supported for RSA-PSS:
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they have exactly the same meaning as for the RSA algorithm.
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Optional parameter restrictions can be specified when generating a PSS key. By
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default no parameter restrictions are placed on the generated key. If any
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restrictions are set (using the macros described below) then B<all> parameters
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are restricted. For example, setting a minimum salt length also restricts the
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digest and MGF1 algorithms. If any restrictions are in place then they are
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reflected in the corresponding parameters of the public key when (for example)
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a certificate request is signed.
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EVP_PKEY_CTX_set_rsa_pss_keygen_md() restricts the digest algorithm the
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generated key can use to B<md>.
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EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md() restricts the MGF1 algorithm the
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generated key can use to B<md>.
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EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen() restricts the minimum salt length
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to B<saltlen>.
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=head1 NOTES
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A context for the B<RSA-PSS> algorithm can be obtained by calling:
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EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA_PSS, NULL);
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The public key format is documented in RFC4055.
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The PKCS#8 private key format used for RSA-PSS keys is similar to the RSA
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format except it uses the B<id-RSASSA-PSS> OID and the parameters field, if
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present, restricts the key parameters in the same way as the public key.
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=head1 RETURN VALUES
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All these functions return 1 for success and 0 or a negative value for failure.
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In particular a return value of -2 indicates the operation is not supported by
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the public key algorithm.
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new(3)>,
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L<EVP_PKEY_CTX_ctrl_str(3)>,
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L<EVP_PKEY_derive(3)>
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=head1 COPYRIGHT
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Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (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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