core: Use FreeBSD's public domain SHA1 instead of OpenSSL's so that jettisoning OpenSSL is an option.

src/sha1.h

@@ -0,0 +1,71 @@
+/*
+ * SHA1 internal definitions
+ * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+/**
+** \defgroup sha1 SHA1
+** SHA1 API.
+** Adapted from
+** https://web.mit.edu/freebsd/head/contrib/wpa/src/crypto/sha1_i.h by Cory
+** McWilliams 2025-09-28.
+** @{
+*/
+
+#ifndef SHA1_I_H
+#define SHA1_I_H
+
+#include <inttypes.h>
+
+/**
+** SHA1 context struct.
+*/
+struct SHA1Context
+{
+	/** SHA1 state. */
+	uint32_t state[5];
+	/** SHA1 count. */
+	uint32_t count[2];
+	/** SHA1 buffer. */
+	unsigned char buffer[64];
+};
+
+/**
+** SHA1 context.
+*/
+typedef struct SHA1Context SHA1_CTX;
+
+/**
+** Initialize a SHA1 context.
+** @param context The context.
+*/
+void SHA1Init(struct SHA1Context* context);
+
+/**
+** Calculate an ongoing hash for a block of data.
+** @param context The SHA1 context.
+** @param data The data to hash.
+** @param len The length of data.
+*/
+void SHA1Update(struct SHA1Context* context, const void* data, uint32_t len);
+
+/**
+** Calculate the final hash digest.
+** @param digest Populated with the digest.
+** @param context The SHA1 context.
+*/
+void SHA1Final(unsigned char digest[20], struct SHA1Context* context);
+
+/**
+** Perform a SHA1 transformation.
+** @param state The SHA1 state.
+** @param buffer The data.
+*/
+void SHA1Transform(uint32_t state[5], const unsigned char buffer[64]);
+
+#endif /* SHA1_I_H */
+
+/** @} */