diff --git a/libexec/flua/Makefile b/libexec/flua/Makefile
--- a/libexec/flua/Makefile
+++ b/libexec/flua/Makefile
@@ -18,7 +18,8 @@
# FreeBSD Extensions
.PATH: ${.CURDIR}/modules
SRCS+= linit_flua.c
-SRCS+= lfs.c lposix.c lfbsd.c
+SRCS+= lfs.c lposix.c lfbsd.c lhash.c
+LIBADD+= md
CFLAGS+= -I${SRCTOP}/lib/liblua -I${.CURDIR}/modules -I${LUASRC}
CFLAGS+= -DLUA_PROGNAME="\"${PROG}\""
diff --git a/libexec/flua/linit_flua.c b/libexec/flua/linit_flua.c
--- a/libexec/flua/linit_flua.c
+++ b/libexec/flua/linit_flua.c
@@ -36,6 +36,7 @@
#include "lfs.h"
#include "lposix.h"
#include "lfbsd.h"
+#include "lhash.h"
#include "lua_ucl.h"
/*
@@ -62,6 +63,7 @@
{"posix.unistd", luaopen_posix_unistd},
{"ucl", luaopen_ucl},
{"fbsd", luaopen_fbsd},
+ {"hash", luaopen_hash},
{NULL, NULL}
};
diff --git a/libexec/flua/modules/lhash.h b/libexec/flua/modules/lhash.h
new file mode 100644
--- /dev/null
+++ b/libexec/flua/modules/lhash.h
@@ -0,0 +1,11 @@
+/*-
+ * Copyright (c) 2024 Netflix, Inc
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <lua.h>
+
+int luaopen_hash(lua_State *L);
diff --git a/libexec/flua/modules/lhash.c b/libexec/flua/modules/lhash.c
new file mode 100644
--- /dev/null
+++ b/libexec/flua/modules/lhash.c
@@ -0,0 +1,169 @@
+/*-
+ * Copyright (c) 2024 Netflix, Inc
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <lua.h>
+#include "lauxlib.h"
+#include "lhash.h"
+
+#include <sha256.h>
+#include <string.h>
+
+#define SHA256_META "SHA256 meta table"
+#define SHA256_DIGEST_LEN 32
+
+/*
+ * Note C++ comments indicate the before -- after state of the stack, in with a
+ * similar convention to forth's ( ) comments. Lua indexes are from 1 and can be
+ * read left to right (leftmost is 1). Negative are relative to the end (-1 is
+ * rightmost). A '.' indicates a return value left on the stack (all values to
+ * its right). Trivial functions don't do this.
+ */
+
+/*
+ * Updates the digest with the new data passed in. Takes 1 argument, which
+ * is converted to a string.
+ */
+static int
+lua_sha256_update(lua_State *L)
+{
+ size_t len;
+ const unsigned char *data;
+ SHA256_CTX *ctx;
+
+ ctx = luaL_checkudata(L, 1, SHA256_META);
+ data = luaL_checklstring(L, 2, &len);
+ SHA256_Update(ctx, data, len);
+
+ lua_pushvalue(L, 1);
+
+ return (1);
+}
+
+/*
+ * Finalizes the digest value and returns it as a 32-byte binary string. The ctx
+ * is zeroed.
+ */
+static int
+lua_sha256_digest(lua_State *L)
+{
+ SHA256_CTX *ctx;
+ unsigned char digest[SHA256_DIGEST_LEN];
+
+ ctx = luaL_checkudata(L, 1, SHA256_META);
+ SHA256_Final(digest, ctx);
+ lua_pushlstring(L, digest, sizeof(digest));
+
+ return (1);
+}
+
+/*
+ * Finalizes the digest value and returns it as a 64-byte ascii string of hex
+ * numbers. The ctx is zeroed.
+ */
+static int
+lua_sha256_hexdigest(lua_State *L)
+{
+ SHA256_CTX *ctx;
+ char hexdigest[SHA256_DIGEST_LEN * 2 + 1];
+
+ ctx = luaL_checkudata(L, 1, SHA256_META);
+ SHA256_End(ctx, hexdigest);
+ lua_pushstring(L, hexdigest);
+
+ return (1);
+}
+
+/*
+ * Zeros out the ctx before garbage collection. Normally this is done in
+ * obj:digest or obj:hexdigest, but if not, it will be wiped here. Lua
+ * manages freeing the ctx memory.
+ */
+static int
+lua_sha256_done(lua_State *L)
+{
+ SHA256_CTX *ctx;
+
+ ctx = luaL_checkudata(L, 1, SHA256_META);
+ memset(ctx, 0, sizeof(*ctx));
+
+ return (0);
+}
+
+/*
+ * Create object obj which accumulates the state of the sha256 digest
+ * for its contents and any subsequent obj:update call. It takes zero
+ * or 1 arguments.
+ */
+static int
+lua_sha256(lua_State *L)
+{
+ SHA256_CTX *ctx;
+ int top;
+
+ /* We take 0 or 1 args */
+ top = lua_gettop(L); // data -- data
+ if (top > 1) {
+ lua_pushnil(L);
+ return (1);
+ }
+
+ ctx = lua_newuserdata(L, sizeof(*ctx)); // data -- data ctx
+ SHA256_Init(ctx);
+ if (top == 1) {
+ size_t len;
+ const unsigned char *data;
+
+ data = luaL_checklstring(L, 1, &len);
+ SHA256_Update(ctx, data, len);
+ }
+ luaL_getmetatable(L, SHA256_META); // data ctx -- data ctx meta
+ lua_setmetatable(L, -2); // data ctx -- data ctx
+
+ return (1); // data . ctx
+}
+
+/*
+ * Setup the metatable to manage our userdata that we create in lua_sha256. We
+ * request a finalization call with __gc so we can zero out the ctx buffer so
+ * that we don't leak secrets if obj:digest or obj:hexdigest aren't called.
+ */
+static void
+register_metatable_sha256(lua_State *L)
+{
+ luaL_newmetatable(L, SHA256_META); // -- meta
+
+ lua_newtable(L); // meta -- meta tbl
+ lua_pushcfunction(L, lua_sha256_update); // meta tbl -- meta tbl fn
+ lua_setfield(L, -2, "update"); // meta tbl fn -- meta tbl
+ lua_pushcfunction(L, lua_sha256_digest); // meta tbl -- meta tbl fn
+ lua_setfield(L, -2, "digest"); // meta tbl fn -- meta tbl
+ lua_pushcfunction(L, lua_sha256_hexdigest); // meta tbl -- meta tbl fn
+ lua_setfield(L, -2, "hexdigest"); // meta tbl fn -- meta tbl
+
+ /* Associate tbl with metatable */
+ lua_setfield(L, -2, "__index"); // meta tbl -- meta
+ lua_pushcfunction(L, lua_sha256_done); // meta -- meta fn
+ lua_setfield(L, -2, "__gc"); // meta fn -- meta
+
+ lua_pop(L, 1); // meta --
+}
+
+#define REG_SIMPLE(n) { #n, lua_ ## n }
+static const struct luaL_Reg hashlib[] = {
+ REG_SIMPLE(sha256),
+ { NULL, NULL },
+};
+#undef REG_SIMPLE
+
+int
+luaopen_hash(lua_State *L)
+{
+ register_metatable_sha256(L);
+
+ luaL_newlib(L, hashlib);
+
+ return 1;
+}
diff --git a/libexec/flua/modules/lposix.c b/libexec/flua/modules/lposix.c
--- a/libexec/flua/modules/lposix.c
+++ b/libexec/flua/modules/lposix.c
@@ -24,7 +24,6 @@
*
*/
-#include <sys/cdefs.h>
#include <sys/stat.h>
#include <errno.h>