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https://github.com/CloverHackyColor/CloverBootloader.git
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189 lines
5.5 KiB
Plaintext
189 lines
5.5 KiB
Plaintext
=pod
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=head1 NAME
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EVP_KDF-SS - The Single Step / One Step EVP_KDF implementation
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=head1 DESCRIPTION
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The EVP_KDF-SS algorithm implements the Single Step key derivation function (SSKDF).
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SSKDF derives a key using input such as a shared secret key (that was generated
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during the execution of a key establishment scheme) and fixedinfo.
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SSKDF is also informally referred to as 'Concat KDF'.
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=head2 Auxiliary function
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The implementation uses a selectable auxiliary function H, which can be one of:
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=over 4
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=item B<H(x) = hash(x, digest=md)>
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=item B<H(x) = HMAC_hash(x, key=salt, digest=md)>
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=item B<H(x) = KMACxxx(x, key=salt, custom="KDF", outlen=mac_size)>
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=back
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Both the HMAC and KMAC implementations set the key using the 'salt' value.
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The hash and HMAC also require the digest to be set.
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=head2 Identity
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"SSKDF" is the name for this implementation; it
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can be used with the EVP_KDF_fetch() function.
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=head2 Supported parameters
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The supported parameters are:
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=over 4
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=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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This parameter is ignored for KMAC.
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=item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
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=item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
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=item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
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These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
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=item "key" (B<EVP_KDF_CTRL_SET_KEY>) <octet string>
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This parameter set the shared secret that is used for key derivation.
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=item "info" (B<OSSL_KDF_PARAM_INFO>) <octet string>
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This parameter sets an optional value for fixedinfo, also known as otherinfo.
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=back
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=head1 NOTES
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A context for SSKDF can be obtained by calling:
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EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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The output length of an SSKDF is specified via the I<keylen>
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parameter to the L<EVP_KDF_derive(3)> function.
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=head1 EXAMPLES
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This example derives 10 bytes using H(x) = SHA-256, with the secret key "secret"
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and fixedinfo value "label":
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EVP_KDF *kdf;
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EVP_KDF_CTX *kctx;
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unsigned char out[10];
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OSSL_PARAM params[4], *p = params;
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kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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SN_sha256, strlen(SN_sha256));
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
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"secret", (size_t)6);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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"label", (size_t)5);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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error("EVP_KDF_derive");
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}
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EVP_KDF_CTX_free(kctx);
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This example derives 10 bytes using H(x) = HMAC(SHA-256), with the secret key "secret",
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fixedinfo value "label" and salt "salt":
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EVP_KDF *kdf;
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EVP_KDF_CTX *kctx;
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unsigned char out[10];
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OSSL_PARAM params[6], *p = params;
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kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
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SN_hmac, strlen(SN_hmac));
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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SN_sha256, strlen(SN_sha256));
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*p++ = OSSL_PARAM_construct_octet_string(EVP_KDF_CTRL_SET_KEY,
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"secret", (size_t)6);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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"label", (size_t)5);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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"salt", (size_t)4);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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error("EVP_KDF_derive");
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}
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EVP_KDF_CTX_free(kctx);
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This example derives 10 bytes using H(x) = KMAC128(x,salt,outlen), with the secret key "secret"
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fixedinfo value "label", salt of "salt" and KMAC outlen of 20:
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EVP_KDF *kdf;
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EVP_KDF_CTX *kctx;
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unsigned char out[10];
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OSSL_PARAM params[6], *p = params;
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kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
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SN_kmac128, strlen(SN_kmac128));
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*p++ = OSSL_PARAM_construct_octet_string(EVP_KDF_CTRL_SET_KEY,
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"secret", (size_t)6);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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"label", (size_t)5);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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"salt", (size_t)4);
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*p++ = OSSL_PARAM_construct_size_t(OSSL_KDF_PARAM_MAC_SIZE, (size_t)20);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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error("EVP_KDF_derive");
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}
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EVP_KDF_CTX_free(kctx);
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=head1 CONFORMING TO
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NIST SP800-56Cr1.
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=head1 SEE ALSO
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L<EVP_KDF(3)>,
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L<EVP_KDF_CTX_new(3)>,
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L<EVP_KDF_CTX_free(3)>,
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L<EVP_KDF_CTX_set_params(3)>,
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L<EVP_KDF_CTX_get_kdf_size(3)>,
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L<EVP_KDF_derive(3)>,
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L<EVP_KDF(3)/PARAMETERS>
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=head1 HISTORY
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This functionality was added in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved. Copyright
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(c) 2019, Oracle and/or its affiliates. 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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