contrib: add safe_getenv() support to spd_readdir

This is part of a series of improvements from a 2008 version of
spd_readdir.c that somehow didn't make it into the version which we
checked into e2fsprogs git tree.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 32 insertions, 2 deletions

diff --git a/contrib/spd_readdir.c b/contrib/spd_readdir.c
index f89832cd..30c01b33 100644
--- a/contrib/spd_readdir.c
+++ b/contrib/spd_readdir.c
@@ -27,6 +27,10 @@
 #define MAX_DIRSIZE	0
 
 #define DEBUG
+/* Util we autoconfiscate spd_readdir... */
+#define HAVE___SECURE_GETENV	1
+#define HAVE_PRCTL		1
+#define HAVE_SYS_PRCTL_H	1
 
 #ifdef DEBUG
 #define DEBUG_DIR(x)	{if (do_debug) { x; }}
@@ -46,6 +50,11 @@
 #include <dirent.h>
 #include <errno.h>
 #include <dlfcn.h>
+#ifdef HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#else
+#define PR_GET_DUMPABLE 3
+#endif
 
 struct dirent_s {
 	unsigned long long d_ino;
@@ -83,6 +92,27 @@ static int num_open = 0;
 static int do_debug = 0;
 #endif
 
+static char *safe_getenv(const char *arg)
+{
+	if ((getuid() != geteuid()) || (getgid() != getegid()))
+		return NULL;
+#if HAVE_PRCTL
+	if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
+		return NULL;
+#else
+#if (defined(linux) && defined(SYS_prctl))
+	if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
+		return NULL;
+#endif
+#endif
+
+#if HAVE___SECURE_GETENV
+	return __secure_getenv(arg);
+#else
+	return getenv(arg);
+#endif
+}
+
 static void setup_ptr()
 {
 	char *cp;
@@ -97,11 +127,11 @@ static void setup_ptr()
 	real_telldir = dlsym(RTLD_NEXT, "telldir");
 	real_seekdir = dlsym(RTLD_NEXT, "seekdir");
 	real_dirfd = dlsym(RTLD_NEXT, "dirfd");
-	if ((cp = getenv("SPD_READDIR_MAX_SIZE")) != NULL) {
+	if ((cp = safe_getenv("SPD_READDIR_MAX_SIZE")) != NULL) {
 		max_dirsize = atol(cp);
 	}
 #ifdef DEBUG
-	if (getenv("SPD_READDIR_DEBUG")) {
+	if (safe_getenv("SPD_READDIR_DEBUG")) {
 		printf("initialized!\n");
 		do_debug++;
 	}