From bd1ad65704d44e3e06a587a890e8087bfd9abe3b Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Sat, 3 Apr 2021 18:32:07 +0200
Subject: Added strnlen for buffer overflow prevention

---
 libs/libc/inc/str.h |  2 ++
 libs/libc/str.c     | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

(limited to 'libs')

diff --git a/libs/libc/inc/str.h b/libs/libc/inc/str.h
index b00750b..542e586 100644
--- a/libs/libc/inc/str.h
+++ b/libs/libc/inc/str.h
@@ -6,6 +6,7 @@
 #include <def.h>
 
 u32 strlen(const char *s) NONNULL;
+u32 strnlen(const char *s, u32 max) NONNULL;
 u32 strlcpy(char *dst, const char *src, u32 size) NONNULL;
 char *strchr(char *s, char c) NONNULL;
 char *strrchr(char *s, char c) NONNULL;
@@ -18,6 +19,7 @@ char *strdup(const char *s) NONNULL;
 #ifdef KERNEL
 
 u32 strlen_user(const char *s) NONNULL;
+u32 strnlen_user(const char *s, u32 max) NONNULL;
 u32 strlcpy_user(char *dst, const char *src, u32 size) NONNULL;
 char *strchr_user(char *s, char c) NONNULL;
 char *strrchr_user(char *s, char c) NONNULL;
diff --git a/libs/libc/str.c b/libs/libc/str.c
index 52af5c4..9a30e92 100644
--- a/libs/libc/str.c
+++ b/libs/libc/str.c
@@ -13,6 +13,16 @@ u32 strlen(const char *str)
 	return s - str;
 }
 
+u32 strnlen(const char *str, u32 max)
+{
+	const char *s = str;
+	while (max && *s) {
+		s++;
+		max--;
+	}
+	return s - str;
+}
+
 u32 strlcpy(char *dst, const char *src, u32 size)
 {
 	const char *orig = src;
@@ -231,6 +241,14 @@ u32 strlen_user(const char *str)
 	return ret;
 }
 
+u32 strnlen_user(const char *str, u32 max)
+{
+	stac();
+	u32 ret = strnlen(str, max);
+	clac();
+	return ret;
+}
+
 u32 strlcpy_user(char *dst, const char *src, u32 size)
 {
 	stac();
-- 
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