Squashed commit of the following:v0.1.2

commit 1c26ef86a04690120f4f752c7c5018a570ec5880
Author: vnugent <public@vaughnnugent.com>
Date:   Wed May 29 13:34:20 2024 -0400

    missed extra argument

commit 88c9095743a12cf8fc1793c607ba3a1e4fa86483
Author: vnugent <public@vaughnnugent.com>
Date:   Wed May 29 13:25:51 2024 -0400

    refactor!: return NC_SUCCESS when validating secret key

commit 718be80a4810b9352de7eb0707da54020aa6b649
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 27 14:52:41 2024 -0400

    fix: Properly build mbedtls & cmake fixes

commit a8a6efb2319f739e5faae550561dc27d9dd1e88d
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 26 17:39:40 2024 -0400

    chore: Update libs, reorder files, internalize private headers

commit 72e1b7be4031e2fd4d258fcf434ad049c0029201
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 26 13:39:08 2024 -0400

    fix: Add c++ extern prototypes in noscrypt.h

commit aeaac8d328b75911541be64d6f09d58fca294a08
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 26 11:47:17 2024 -0400

    refactor: Dep update, openssl chacha20 added

commit 86b02540cce6015cfe4a2a56499a9a2f45d4e368
Author: vnugent <public@vaughnnugent.com>
Date:   Sat May 18 12:24:17 2024 -0400

    refactor: Remove NCContext structure definition

commit d09d9330415d463ca19be9394b02ce11b3366f7e
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 13 22:33:50 2024 -0400

    fix: update mbedtls inline issue includes

commit 7838cb4bb15d4f453f92f56ece75e2b03986fe42
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 13 22:29:16 2024 -0400

    fix: force fPIC for secp256k1 targets

commit d76f7708bc6ae81a638ca708230ac9153ac754e2
Merge: aa8033d a526139
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 12 00:37:01 2024 -0400

    Merge branch 'master' into develop

commit aa8033d4dbfebeb72b6fd7a0cd218ebde0eb54dd
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 12 00:34:20 2024 -0400

    Final overview and test before tag

commit 4e3ead2cf1d3068e77f0959dfdc17e20e9102a0f
Merge: 2cee801 872c49d
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 6 22:08:09 2024 -0400

    Merge branch 'master' into develop

commit 2cee801979bfbcb3b0e53f592ce8c779b57cb679
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 6 22:02:39 2024 -0400

    Ensure static and dynamic libs get same args

commit f533694023133552d0d42933d779c95a5854343f
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 6 21:50:29 2024 -0400

    feat: CMake install & fetch-content test & updates

commit 940ff20348b13d0bc30d9e9f4289dd6de20b16ba
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 5 14:07:28 2024 -0400

    codeberg readonly push

commit b34ed055c0b7d143561ce8798e0a95313b9224bd
Merge: 0a40e20 e737556
Author: vnugent <public@vaughnnugent.com>
Date:   Sat May 4 14:06:45 2024 -0400

    Merge branch 'master' into develop

commit 0a40e209d03e8ff9b6f81cd5969d3e845c633bfc
Author: vnugent <public@vaughnnugent.com>
Date:   Sat May 4 13:55:19 2024 -0400

    ci: Force disable testing for win ci builds

commit 55fae189fffc86f07a3448370f0a746670819712
Author: vnugent <public@vaughnnugent.com>
Date:   Thu May 2 21:54:35 2024 -0400

    feat: Working and tested openssl impl & defaults

commit 6ff8bb11774c51fd341b7699a3938fd894995fbf
Author: vnugent <public@vaughnnugent.com>
Date:   Thu Apr 25 17:45:42 2024 -0400

    refactor: Finish support and testing for mbedtls

commit 7cb7a93de4f6f5e741bc5129e3d928e44f050930
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Apr 23 18:19:31 2024 -0400

    refactor!: MbedTLS on Windows, switch to uint32

commit 30e8dda6cbea86bdee6d5dfe48514385d3b9f81b
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Apr 23 14:48:05 2024 -0400

    refactor: Crypto dep redesign working on Windows

commit d09c6c1bd5da3e2d79351daeba304ca99976a726
Author: vnugent <public@vaughnnugent.com>
Date:   Thu Apr 18 00:28:51 2024 -0400

    refactor!: Pushing what I have to dev

commit 54e06ada7d624ed0d28c6a6db04a149708841bf8
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Apr 13 01:24:00 2024 -0400

    fix: convert constants to hex, inline macro, ParseErrorCode

commit 4215e3100d9a0d23119080d09638fa5b60d0c6d4
Merge: d3328f4 7485aa5
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Apr 3 18:26:30 2024 -0400

    Merge branch 'master' into develop

commit d3328f4152b22b28f24c43dda62464287f1efff5
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Apr 3 18:22:56 2024 -0400

    build: Included dependency and versions in client builds

commit b11bc0bac955fd5c6db65f0da48456bf5e748805
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Apr 3 18:10:08 2024 -0400

    fix: Fix c89 compatabilty comments and struct assignment

commit 9915bd41799a72413e6b400e150aa9f5fa797e25
Merge: 8e3d6ea 5184d7d
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Mar 30 09:57:30 2024 -0400

    Merge branch 'master' into develop

commit 8e3d6ea5e3c83fe42cb904b6ccc4fe2b73f76aae
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Mar 30 09:52:55 2024 -0400

    refactor!: Some api (struct) changes and updated tests

commit e88e8420520204e20802516f01d4488bb0b1d6ea
Merge: 490dfee 21f6c0a
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Mar 3 15:02:34 2024 -0500

    Merge branch 'master' into develop

commit 490dfee4ef22479009627435c6ad728c3cbbab54
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Mar 3 14:59:25 2024 -0500

    test: #3 tests for encryption/description and Macs

commit efa97490b7ed47f4e2f05bee52e2b33e14e439e6
Merge: 1b84e3c 120022a
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Mar 3 14:55:48 2024 -0500

    merge master

commit 1b84e3c7c2e55b1ff9ffdd09b66873e11c131441
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Mar 2 22:57:36 2024 -0500

    fix: #2 constent usage of sizeof() operator on struct types

commit 9de5a214c66adea0ef2d0bac63c59449de202a88
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Mar 1 14:30:36 2024 -0500

    perf: avoid nc_key struct copy, cast and verify instead

commit b917b761120ed684af28d0707673ffadcf14b8fe
Author: vnugent <public@vaughnnugent.com>
Date:   Mon Feb 12 22:06:50 2024 -0500

    fix: found the constant time memcompare function

commit 9f85fff3b9f25da7410569ea94f994b88feb3910
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Feb 9 22:48:35 2024 -0500

    feat: added/update MAC functions to sign or verify nip44 payload

commit aa5113741bb419b02d6ea416bba571fa3d65db46
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Feb 7 01:37:53 2024 -0500

    add missing hmac-key output buffer

commit 55f47d22cc9ce4d1e22b70814d608c7ef3b1bbc9
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Feb 4 21:08:13 2024 -0500

    simple bug fixes, and public api argument validation tests

commit 73c5a713fb164ae8b4ac8a891a8020e08eae0a3b
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Feb 2 23:05:48 2024 -0500

    update api to return secpvalidate return code instead of internal return codes

commit 06c73004e1a39a7ea4ea3a89c22dee0f66adb236
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Feb 2 19:25:17 2024 -0500

    change to lgpl license

commit 6e79fdb3b6b6739fc7797d47e55a7691306cf736
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Jan 31 21:30:49 2024 -0500

    move validation macros, and optionally disable them

commit ac1e58837f1ba687939f78b5c03cadd346c10ddd
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Jan 30 12:25:05 2024 -0500

    couple more tests, renable range checks, set flags for all projects

1 files changed, 131 insertions, 0 deletions

diff --git a/src/hkdf.c b/src/hkdf.c
new file mode 100644
index 0000000..0d91d14
--- /dev/null
+++ b/src/hkdf.c
@@ -0,0 +1,131 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: hkdf.c
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+
+#include "hkdf.h"
+
+/* Include string for memmove */
+#include <string.h>
+
+#define HKDF_MIN(a, b) (a < b ? a : b)
+
+STATIC_ASSERT(HKDF_IN_BUF_SIZE > SHA256_DIGEST_SIZE, "HDK Buffer must be at least the size of the underlying hashing alg output")
+
+static _nc_fn_inline void ncWriteSpanS(span_t* span, uint32_t offset, const uint8_t* data, uint32_t size)
+{
+	DEBUG_ASSERT2(span != NULL, "Expected span to be non-null")
+	DEBUG_ASSERT2(data != NULL, "Expected data to be non-null")
+	DEBUG_ASSERT2(offset + size <= span->size, "Expected offset + size to be less than span size")
+
+	/* Copy data to span */
+	memmove(span->data + offset, data, size);
+}
+
+static _nc_fn_inline void debugValidateHandler(const struct nc_hkdf_fn_cb_struct* handler)
+{
+	DEBUG_ASSERT(handler != NULL)
+	DEBUG_ASSERT(handler->update != NULL)
+	DEBUG_ASSERT(handler->finish != NULL)
+}
+
+/*
+* The following functions implements the HKDF expand function using an existing
+* HMAC function.
+*
+* This follows the guidence from RFC 5869: https://tools.ietf.org/html/rfc5869
+*/
+
+cstatus_t hkdfExpandProcess(
+	const struct nc_hkdf_fn_cb_struct* handler,
+	void* ctx,
+	const cspan_t* info,
+	span_t* okm
+)
+{
+	cstatus_t result;
+
+	uint8_t counter;
+	uint32_t tLen, okmOffset;
+	uint8_t t[HKDF_IN_BUF_SIZE];
+	cspan_t tSpan, counterSpan;
+
+	debugValidateHandler(handler);
+
+	ncCryptoSecureZero(t, sizeof(t));
+
+	tLen = 0;				/* T(0) is an empty string(zero length) */
+	okmOffset = 0;
+	counter = 1;			/* counter is offset by 1 for init */
+	result = CSTATUS_FAIL;	/* Start in fail state */
+
+	/* counter as a span */
+	ncSpanInitC(&counterSpan, &counter, sizeof(counter));
+
+	/* Compute T(N) = HMAC(prk, T(n-1) | info | n) */
+	while (okmOffset < okm->size)
+	{
+		ncSpanInitC(&tSpan, t, tLen);
+
+		if (handler->update(ctx, &tSpan) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		if (handler->update(ctx, info) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		if (handler->update(ctx, &counterSpan) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		/* 
+		* Write current hash state to t buffer. It is known
+		* that the t buffer must be at least the size of the
+		* underlying hash function output.
+		*/
+		if (handler->finish(ctx, t) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		/* tlen becomes the hash size or remaining okm size */
+		tLen = HKDF_MIN(okm->size - okmOffset, SHA256_DIGEST_SIZE);
+
+		DEBUG_ASSERT(tLen <= sizeof(t));
+
+		/* write the T buffer back to okm */
+		ncWriteSpanS(okm, okmOffset, t, tLen);
+
+		/* shift base okm pointer by T */
+		okmOffset += tLen;
+
+		/* increment counter */
+		counter++;
+	}
+
+	result = CSTATUS_OK;	/* HMAC operation completed, so set success */
+
+Exit:
+
+	return result;
+}