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[RFC,3/4] libselinux: introduce strlcpy

Message ID 20220510182039.28771-3-cgzones@googlemail.com (mailing list archive)
State New
Headers show
Series [RFC,1/4] libselinux: simplify policy path logic to avoid uninitialized read | expand

Commit Message

Christian Göttsche May 10, 2022, 6:20 p.m. UTC
To copy string safely, by always NULL-terminating them, and provide an
easy way to check for truncation introduce the nonstandard function
strlcpy(3).  Use the system implementation if available.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
---
 libselinux/src/Makefile           |  6 ++++++
 libselinux/src/selinux_internal.c | 18 ++++++++++++++++++
 libselinux/src/selinux_internal.h |  4 ++++
 3 files changed, 28 insertions(+)
 create mode 100644 libselinux/src/selinux_internal.c
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Patch

diff --git a/libselinux/src/Makefile b/libselinux/src/Makefile
index 04bf4f24..88aa32f8 100644
--- a/libselinux/src/Makefile
+++ b/libselinux/src/Makefile
@@ -103,6 +103,12 @@  FTS_LDLIBS ?=
 
 override CFLAGS += -I../include -D_GNU_SOURCE $(DISABLE_FLAGS) $(PCRE_CFLAGS)
 
+# check for strlcpy(3) availability
+H := \#
+ifeq (yes,$(shell printf '${H}include <string.h>\nint main(void){char*d,*s;strlcpy(d, s, 0);return 0;}' | $(CC) -x c -o /dev/null - >/dev/null 2>&1 && echo yes))
+override CFLAGS += -DHAVE_STRLCPY
+endif
+
 SWIG_CFLAGS += -Wno-error -Wno-unused-variable -Wno-unused-but-set-variable -Wno-unused-parameter \
 		-Wno-shadow -Wno-uninitialized -Wno-missing-prototypes -Wno-missing-declarations \
 		-Wno-deprecated-declarations
diff --git a/libselinux/src/selinux_internal.c b/libselinux/src/selinux_internal.c
new file mode 100644
index 00000000..c2be7c0a
--- /dev/null
+++ b/libselinux/src/selinux_internal.c
@@ -0,0 +1,18 @@ 
+#include "selinux_internal.h"
+
+#include <string.h>
+
+
+#ifndef HAVE_STRLCPY
+size_t strlcpy(char *dest, const char *src, size_t size)
+{
+	size_t ret = strlen(src);
+
+	if (size) {
+		size_t len = (ret >= size) ? size - 1 : ret;
+		memcpy(dest, src, len);
+		dest[len] = '\0';
+	}
+	return ret;
+}
+#endif /* HAVE_STRLCPY */
diff --git a/libselinux/src/selinux_internal.h b/libselinux/src/selinux_internal.h
index 9f4c9073..06f2c038 100644
--- a/libselinux/src/selinux_internal.h
+++ b/libselinux/src/selinux_internal.h
@@ -94,4 +94,8 @@  extern int selinux_page_size ;
 
 extern int has_selinux_config ;
 
+#ifndef HAVE_STRLCPY
+size_t strlcpy(char *dest, const char *src, size_t size);
+#endif
+
 #endif /* SELINUX_INTERNAL_H_ */