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>

diff --git a/contrib/spd_readdir.c b/contrib/spd_readdir.c
index f89832c..30c01b3 100644 (file)
--- 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++;
        }