From 0a5383ccdf8e87d2259d02a9ff44420b3bc3f58d Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Fri, 23 Aug 2019 01:29:52 +0200
Subject: Add wrappers for calloc style functions with size overflow checking

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
 include/util.h    | 16 ++++++++++++++++
 lib/Makemodule.am |  2 +-
 lib/util/alloc.c  | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+), 1 deletion(-)
 create mode 100644 lib/util/alloc.c

diff --git a/include/util.h b/include/util.h
index ae8c43c..ba95b03 100644
--- a/include/util.h
+++ b/include/util.h
@@ -115,4 +115,20 @@ int padd_file(int outfd, uint64_t size, size_t blocksize);
  */
 uint32_t get_source_date_epoch(void);
 
+/*
+  Helper for allocating data structures with flexible array members.
+
+  'base_size' is the size of the struct itself, 'item_size' the size of a
+  single array element and 'nmemb' the number of elements.
+
+  Iternally checks for arithmetic overflows when allocating the combined thing.
+ */
+void *alloc_flex(size_t base_size, size_t item_size, size_t nmemb);
+
+/* Basically the same as calloc, but *ALWAYS* does overflow checking */
+void *alloc_array(size_t item_size, size_t nmemb);
+
+/* allocates len + 1 (for the null-terminator) and does overflow checking */
+void *alloc_string(size_t len);
+
 #endif /* UTIL_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index 6301435..fb9d613 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -47,7 +47,7 @@ libutil_a_SOURCES += lib/util/read_data.c include/util.h
 libutil_a_SOURCES += lib/util/print_version.c lib/util/mkdir_p.c
 libutil_a_SOURCES += lib/util/str_table.c include/str_table.h
 libutil_a_SOURCES += lib/util/dirstack.c lib/util/padd_file.c
-libutil_a_SOURCES += lib/util/read_data_at.c
+libutil_a_SOURCES += lib/util/read_data_at.c lib/util/alloc.c
 libutil_a_SOURCES += lib/util/source_date_epoch.c
 libutil_a_CFLAGS = $(AM_CFLAGS)
 libutil_a_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/lib/util/alloc.c b/lib/util/alloc.c
new file mode 100644
index 0000000..2d748a7
--- /dev/null
+++ b/lib/util/alloc.c
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * alloc.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "util.h"
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <errno.h>
+
+void *alloc_flex(size_t base_size, size_t item_size, size_t nmemb)
+{
+	size_t size;
+
+	if (SZ_MUL_OV(nmemb, item_size, &size)) {
+		errno = EOVERFLOW;
+		return NULL;
+	}
+
+	if (SZ_ADD_OV(base_size, size, &size)) {
+		errno = EOVERFLOW;
+		return NULL;
+	}
+
+	return calloc(1, size);
+}
+
+void *alloc_array(size_t item_size, size_t nmemb)
+{
+	size_t size;
+
+	if (SZ_MUL_OV(nmemb, item_size, &size)) {
+		errno = EOVERFLOW;
+		return NULL;
+	}
+
+	return calloc(1, size);
+}
+
+void *alloc_string(size_t len)
+{
+	size_t size;
+
+	if (SZ_ADD_OV(len, 1, &size)) {
+		errno = EOVERFLOW;
+		return NULL;
+	}
+
+	return calloc(1, len);
+}
-- 
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