From eae496a72e270fd7af411714738e99a7fadfd19b Mon Sep 17 00:00:00 2001
From: Rickard Green <rickard@erlang.org>
Date: Wed, 6 Sep 2017 17:00:14 +0200
Subject: Don't allow null in filenames

---
 erts/emulator/beam/erl_unicode.c | 58 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 53 insertions(+), 5 deletions(-)

(limited to 'erts/emulator/beam/erl_unicode.c')

diff --git a/erts/emulator/beam/erl_unicode.c b/erts/emulator/beam/erl_unicode.c
index 2d1d1443a7..efd2ca3db2 100644
--- a/erts/emulator/beam/erl_unicode.c
+++ b/erts/emulator/beam/erl_unicode.c
@@ -1988,7 +1988,7 @@ char *erts_convert_filename_to_encoding(Eterm name, char *statbuf, size_t statbu
 	is_list(name) || 
 	(allow_empty && is_nil(name))) {
 	Sint need;
-	if ((need = erts_native_filename_need(name,encoding)) < 0) {
+	if ((need = erts_native_filename_need(name, encoding, 0)) < 0) {
 	    return NULL;
 	}
 	if (encoding == ERL_FILENAME_WIN_WCHAR) {
@@ -2152,12 +2152,13 @@ Eterm erts_convert_native_to_filename(Process *p, byte *bytes)
 }
 
 
-Sint erts_native_filename_need(Eterm ioterm, int encoding) 
+Sint erts_native_filename_need(Eterm ioterm, int encoding, int allow_null) 
 {
     Eterm *objp;
     Eterm obj;
     DECLARE_ESTACK(stack);
     Sint need = 0;
+    int seen_null = 0;
 
     if (is_atom(ioterm)) {
 	Atom* ap;
@@ -2194,6 +2195,24 @@ Sint erts_native_filename_need(Eterm ioterm, int encoding)
 	default:
 	    need = -1;
 	}
+        if (!allow_null) {
+            /*
+             * Do not allow null in
+             * the middle of filenames
+             */
+            if (need > 0) {
+                byte *name = ap->name;
+                int len = ap->len;
+                for (i = 0; i < len; i++) {
+                    if (name[i] == 0)
+                        seen_null = 1;
+                    else if (seen_null) {
+                        need = -1;
+                        break;
+                    }
+                }
+            }
+        }
 	DESTROY_ESTACK(stack);
 	return need;
     }
@@ -2224,6 +2243,18 @@ L_Again:   /* Restart with sublist, old listend was pushed on stack */
 		if (is_small(obj)) { /* Always small */
 		    for(;;) {
 			Uint x = unsigned_val(obj);
+                        if (!allow_null) {
+                            /*
+                             * Do not allow null in
+                             * the middle of filenames
+                             */
+                            if (x == 0)
+                                seen_null = 1;
+                            else if (seen_null) {
+                                DESTROY_ESTACK(stack);
+                                return ((Sint) -1);
+                            }
+                        }
 			switch (encoding) {
 			case ERL_FILENAME_LATIN1:
 			    if (x > 255) {
@@ -2515,6 +2546,7 @@ BIF_RETTYPE prim_file_internal_name2native_1(BIF_ALIST_1)
 	BIF_ERROR(BIF_P,BADARG);
     }
     if (is_binary(BIF_ARG_1)) {
+        int seen_null = 0;
 	byte *temp_alloc = NULL;
 	byte *bytes;
 	byte *err_pos;
@@ -2524,10 +2556,18 @@ BIF_RETTYPE prim_file_internal_name2native_1(BIF_ALIST_1)
 	size = binary_size(BIF_ARG_1);
 	bytes = erts_get_aligned_binary_bytes(BIF_ARG_1, &temp_alloc);
 	if (encoding != ERL_FILENAME_WIN_WCHAR) {
+            Uint i;
 	    /*Add 0 termination only*/
 	    bin_term = new_binary(BIF_P, NULL, size+1);
 	    bin_p = binary_bytes(bin_term);
-	    memcpy(bin_p,bytes,size);
+            for (i = 0; i < size; i++) {
+                /* Don't allow null in the middle of filenames... */
+                if (bytes[i] == 0)
+                    seen_null = 1;
+                else if (seen_null)
+                    goto bin_name_error;
+                bin_p[i] = bytes[i];
+            }
 	    bin_p[size]=0;
 	    erts_free_aligned_binary_bytes(temp_alloc);
 	    BIF_RET(bin_term);
@@ -2541,6 +2581,11 @@ BIF_RETTYPE prim_file_internal_name2native_1(BIF_ALIST_1)
 	    bin_term = new_binary(BIF_P, 0, (size+1)*2);
 	    bin_p = binary_bytes(bin_term);
 	    while (size--) {
+                /* Don't allow null in the middle of filenames... */
+                if (*bytes == 0)
+                    seen_null = 1;
+                else if (seen_null)
+                    goto bin_name_error;
 		*bin_p++ = *bytes++;
 		*bin_p++ = 0;
 	    }
@@ -2558,11 +2603,14 @@ BIF_RETTYPE prim_file_internal_name2native_1(BIF_ALIST_1)
 	bin_p[num_chars*2+1] = 0;
 	erts_free_aligned_binary_bytes(temp_alloc);
 	BIF_RET(bin_term);
+    bin_name_error:
+        erts_free_aligned_binary_bytes(temp_alloc);
+        BIF_ERROR(BIF_P,BADARG);
     } /* binary */   
 	    
 
-    if ((need = erts_native_filename_need(BIF_ARG_1,encoding)) < 0) {
-	BIF_ERROR(BIF_P,BADARG);
+    if ((need = erts_native_filename_need(BIF_ARG_1, encoding, 0)) < 0) {
+        BIF_ERROR(BIF_P,BADARG);
     }
     if (encoding == ERL_FILENAME_WIN_WCHAR) {
 	need += 2;
-- 
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