@@ -, +, @@ 
---
 configure.ac                |  3 +++
 libpam/include/missing.h    | 12 ++++++++++++
 modules/pam_exec/pam_exec.c |  1 +
 3 files changed, 16 insertions(+)
 create mode 100644 libpam/include/missing.h
--- a/configure.ac	
+++ a/configure.ac	
@@ -599,6 +599,9 @@ dnl
 AC_CHECK_DECL(__NR_keyctl, [have_key_syscalls=1],[have_key_syscalls=0],[#include <sys/syscall.h>])
 AC_CHECK_DECL(ENOKEY, [have_key_errors=1],[have_key_errors=0],[#include <errno.h>])
 
+# musl and bionic don't have strndupa
+AC_CHECK_DECLS_ONCE([strndupa])
+
 HAVE_KEY_MANAGEMENT=0
 if test $have_key_syscalls$have_key_errors = 11
 then
--- a/libpam/include/missing.h	
+++ a/libpam/include/missing.h	
@@ -0,0 +1,12 @@ 
+#pragma once
+
+#if !HAVE_DECL_STRNDUPA
+#define strndupa(s, n)                                                  \
+        ({                                                              \
+                const char *__old = (s);                                \
+                size_t __len = strnlen(__old, (n));                     \
+                char *__new = alloca(__len + 1);                        \
+                __new[__len] = '\0';                                    \
+                memcpy(__new, __old, __len);                            \
+         })
+#endif
--- a/modules/pam_exec/pam_exec.c	
+++ a/modules/pam_exec/pam_exec.c	
@@ -59,6 +59,7 @@ 
 #include <security/pam_modutil.h>
 #include <security/pam_ext.h>
 #include <security/_pam_macros.h>
+#include <missing.h>
 
 #define ENV_ITEM(n) { (n), #n }
 static struct {
--