Add _FORTIFY_SOURCE support for inet_ntop

- Create the __inet_ntop_chk routine that verifies that the builtin size
of the destination buffer is at least as big as the size given by the
user.
- Redirect calls from inet_ntop to __inet_ntop_chk or __inet_ntop_warn
- Update the abilist for this new routine
- Update the manual to mention the new fortification

Reviewed-by: Florian Weimer <fweimer@redhat.com>

4 files changed, 83 insertions, 0 deletions

diff --git a/inet/Makefile b/inet/Makefile
index 79bacddfd5..104b5828bf 100644
--- a/inet/Makefile
+++ b/inet/Makefile
@@ -25,6 +25,8 @@ include ../Makeconfig
 headers := \
   $(wildcard arpa/*.h protocols/*.h) \
   bits/in.h \
+  bits/inet-fortified-decl.h \
+  bits/inet-fortified.h \
   ifaddrs.h \
   netinet/ether.h \
   netinet/icmp6.h \
diff --git a/inet/arpa/inet.h b/inet/arpa/inet.h
index 42d38c330d..3083676f5d 100644
--- a/inet/arpa/inet.h
+++ b/inet/arpa/inet.h
@@ -101,6 +101,11 @@ extern char *inet_nsap_ntoa (int __len, const unsigned char *__cp,
 			     char *__buf) __THROW;
 #endif
 
+#if __USE_FORTIFY_LEVEL > 0 && defined __fortify_function
+/* Include functions with security checks.  */
+#  include <bits/inet-fortified.h>
+#endif
+
 __END_DECLS
 
 #endif /* arpa/inet.h */
diff --git a/inet/bits/inet-fortified-decl.h b/inet/bits/inet-fortified-decl.h
new file mode 100644
index 0000000000..23e3cf4b22
--- /dev/null
+++ b/inet/bits/inet-fortified-decl.h
@@ -0,0 +1,35 @@
+/* Declarations of checking macros for inet functions.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _BITS_INET_FORTIFIED_DEC_H
+#define _BITS_INET_FORTIFIED_DEC_H 1
+
+#ifndef _ARPA_INET_H
+# error "Never include <bits/inet-fortified-decl.h> directly; use <arpa/inet.h> instead."
+#endif
+
+extern const char *__inet_ntop_chk (int, const void *, char *, socklen_t, size_t);
+
+extern const char *__REDIRECT_FORTIFY_NTH (__inet_ntop_alias,
+					   (int, const void *, char *, socklen_t), inet_ntop);
+extern const char *__REDIRECT_NTH (__inet_ntop_chk_warn,
+				   (int, const void *, char *, socklen_t, size_t), __inet_ntop_chk)
+     __warnattr ("inet_ntop called with bigger length than "
+		 "size of destination buffer");
+
+#endif /* bits/inet-fortified-decl.h.  */
diff --git a/inet/bits/inet-fortified.h b/inet/bits/inet-fortified.h
new file mode 100644
index 0000000000..4f6bc34b0f
--- /dev/null
+++ b/inet/bits/inet-fortified.h
@@ -0,0 +1,41 @@
+/* Checking macros for inet functions.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _BITS_INET_FORTIFIED_H
+#define _BITS_INET_FORTIFIED_H 1
+
+#ifndef _ARPA_INET_H
+# error "Never include <bits/inet-fortified.h> directly; use <arpa/inet.h> instead."
+#endif
+
+#include <bits/inet-fortified-decl.h>
+
+__fortify_function __attribute_overloadable__ const char *
+__NTH (inet_ntop (int __af,
+	   __fortify_clang_overload_arg (const void *, __restrict, __src),
+	   char *__restrict __dst, socklen_t __dst_size))
+    __fortify_clang_warning_only_if_bos_lt (__dst_size, __dst,
+					    "inet_ntop called with bigger length "
+					    "than size of destination buffer")
+{
+  return __glibc_fortify (inet_ntop, __dst_size, sizeof (char),
+			  __glibc_objsize (__dst),
+			  __af, __src, __dst, __dst_size);
+};
+
+#endif /* bits/inet-fortified.h.  */