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.tr \(*W- . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\}
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.. .nr rF 0 . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF Fear. Run. Save yourself. No user-serviceable parts.
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Title "EVP_KDF-SSHKDF 7ossl"
way too many mistakes in technical documents.
The \s-1EVP_KDF-SSHKDF\s0 algorithm implements the \s-1SSHKDF\s0 key derivation function. It is defined in \s-1RFC 4253,\s0 section 7.2 and is used by \s-1SSH\s0 to derive IVs, encryption keys and integrity keys. Five inputs are required to perform key derivation: The hashing function (for example \s-1SHA256\s0), the Initial Key, the Exchange Hash, the Session \s-1ID,\s0 and the derivation key type.
0 Item "digest (OSSL_KDF_PARAM_DIGEST) <UTF8 string>" Item "key (OSSL_KDF_PARAM_KEY) <octet string>"
These parameters work as described in \*(L"\s-1PARAMETERS\*(R"\s0 in \s-1EVP_KDF\s0\|(3). Item "xcghash (OSSL_KDF_PARAM_SSHKDF_XCGHASH) <octet string>"
0 Item "session_id (OSSL_KDF_PARAM_SSHKDF_SESSION_ID) <octet string>"
These parameters set the respective values for the \s-1KDF.\s0 If a value is already set, the contents are replaced. Item "type (OSSL_KDF_PARAM_SSHKDF_TYPE) <UTF8 string>" This parameter sets the type for the \s-1SSHKDF\s0 operation. There are six supported types:
.Vb 2 EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SSHKDF", NULL); EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); .Ve
The output length of the \s-1SSHKDF\s0 derivation is specified via the keylen parameter to the EVP_KDF_derive\|(3) function. Since the \s-1SSHKDF\s0 output length is variable, calling EVP_KDF_CTX_get_kdf_size\|(3) to obtain the requisite length is not meaningful. The caller must allocate a buffer of the desired length, and pass that buffer to the \fBEVP_KDF_derive\|(3) function along with the desired length.
.Vb 9 EVP_KDF *kdf; EVP_KDF_CTX *kctx; char type = EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV; unsigned char key[1024] = "01234..."; unsigned char xcghash[32] = "012345..."; unsigned char session_id[32] = "012345..."; unsigned char out[8]; size_t outlen = sizeof(out); OSSL_PARAM params[6], *p = params; \& kdf = EVP_KDF_fetch(NULL, "SSHKDF", NULL); kctx = EVP_KDF_CTX_new(kdf); EVP_KDF_free(kdf); \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, SN_sha256, strlen(SN_sha256)); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY, key, (size_t)1024); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SSHKDF_XCGHASH, xcghash, (size_t)32); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SSHKDF_SESSION_ID, session_id, (size_t)32); *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_SSHKDF_TYPE, &type, sizeof(type)); *p = OSSL_PARAM_construct_end(); if (EVP_KDF_derive(kctx, out, outlen, params) <= 0) /* Error */ .Ve
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.