util/mkhtemp: new utility (hardened mktemp)

part of the same code library as nvmutil.

as part of this, i renamed util/nvmutil
to util/libreboot-utils/ because it is
now a multi-utility codebase.

this is more efficient, since i also wish
to use mkhtemp (function) in nvmutil.

Signed-off-by: Leah Rowe <leah@libreboot.org>

1 files changed, 108 insertions, 0 deletions

diff --git a/util/libreboot-utils/lib/checksum.c b/util/libreboot-utils/lib/checksum.c
new file mode 100644
index 00000000..b417dc7e
--- /dev/null
+++ b/util/libreboot-utils/lib/checksum.c
@@ -0,0 +1,108 @@
+/* SPDX-License-Identifier: MIT
+ * Copyright (c) 2022-2026 Leah Rowe <leah@libreboot.org>
+ *
+ * Functions related to GbE NVM checksums.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <errno.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+#include "../include/common.h"
+
+void
+read_checksums(void)
+{
+	struct xstate *x = xstatus();
+	struct commands *cmd = &x->cmd[x->i];
+	struct xfile *f = &x->f;
+
+	size_t _p;
+	size_t _skip_part;
+
+	unsigned char _num_invalid;
+	unsigned char _max_invalid;
+
+	f->part_valid[0] = 0;
+	f->part_valid[1] = 0;
+
+	if (!cmd->chksum_read)
+		return;
+
+	_num_invalid = 0;
+	_max_invalid = 2;
+
+	if (cmd->arg_part)
+		_max_invalid = 1;
+
+	/* Skip verification on this part,
+	 * but only when arg_part is set.
+	 */
+	_skip_part = f->part ^ 1;
+
+	for (_p = 0; _p < 2; _p++) {
+
+		/* Only verify a part if it was *read*
+		 */
+		if (cmd->arg_part && (_p == _skip_part))
+			continue;
+
+		f->part_valid[_p] = good_checksum(_p);
+		if (!f->part_valid[_p])
+			++_num_invalid;
+	}
+
+	if (_num_invalid >= _max_invalid) {
+
+		if (_max_invalid == 1)
+			err(ECANCELED, "%s: part %lu has a bad checksum",
+			    f->fname, (size_t)f->part);
+
+		err(ECANCELED, "%s: No valid checksum found in file",
+		    f->fname);
+	}
+}
+
+int
+good_checksum(size_t partnum)
+{
+	unsigned short expected_checksum;
+	unsigned short actual_checksum;
+
+	expected_checksum =
+	    calculated_checksum(partnum);
+
+	actual_checksum =
+	    nvm_word(NVM_CHECKSUM_WORD, partnum);
+
+	if (expected_checksum == actual_checksum) {
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+void
+set_checksum(size_t p)
+{
+	check_bin(p, "part number");
+	set_nvm_word(NVM_CHECKSUM_WORD, p, calculated_checksum(p));
+}
+
+unsigned short
+calculated_checksum(size_t p)
+{
+	size_t c;
+	unsigned int val16;
+
+	val16 = 0;
+
+	for (c = 0; c < NVM_CHECKSUM_WORD; c++)
+		val16 += (unsigned int)nvm_word(c, p);
+
+	return (unsigned short)((NVM_CHECKSUM - val16) & 0xffff);
+}