Initial commit

1 files changed, 28 insertions, 0 deletions

diff --git a/spoof_homedir.c b/spoof_homedir.c
new file mode 100644
index 000000000000..caee9b033b2e
--- /dev/null
+++ b/spoof_homedir.c
@@ -0,0 +1,28 @@
+#define _GNU_SOURCE
+#include <dlfcn.h>
+#include <pwd.h>
+#include <sys/types.h>
+
+/* shared library that replaces the home directory for root in a `getpwuid()` call
+ * with a specific location
+ *
+ * inspired by https://rafalcieslak.wordpress.com/2013/04/02/dynamic-linker-tricks-using-ld_preload-to-cheat-inject-features-and-investigate-programs/
+ *
+ * Usage:
+ * gcc -shared -fPIC -D 'FAKE_HOME="/path/to/fake/directory"' spoof_homedir.c -o spoof_homedir.so -ldl
+ * LD_PRELOAD="./spoof_homedir.so" binary_to_spoof
+ */
+
+typedef struct passwd *(*orig_getpwuid_f_type)(uid_t uid);
+
+struct passwd *getpwuid(uid_t uid) {
+	orig_getpwuid_f_type orig_getpwuid;
+	orig_getpwuid = (orig_getpwuid_f_type)dlsym(RTLD_NEXT, "getpwuid");
+
+	struct passwd *result = orig_getpwuid(uid);
+	if (uid == 0) {
+		result->pw_dir = FAKE_HOME;
+	}
+
+	return result;
+}