Fix panic with substr interpolation function by invalid offset

Fixes hashicorp#17041
dhgautam · Jan 5, 2018 · e873af9 · e873af9
1 parent 18975d7
commit e873af9
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Showing 2 changed files with 6 additions and 1 deletion.
diff --git a/config/interpolate_funcs.go b/config/interpolate_funcs.go
@@ -1577,7 +1577,7 @@ func interpolationFuncSubstr() ast.Function {
 				return nil, fmt.Errorf("length should be a non-negative integer")
 			}
 
-			if offset > len(str) {
+			if offset > len(str) || offset < 0 {
 				return nil, fmt.Errorf("offset cannot be larger than the length of the string")
 			}
 

diff --git a/config/interpolate_funcs_test.go b/config/interpolate_funcs_test.go
@@ -2568,6 +2568,11 @@ func TestInterpolateFuncSubstr(t *testing.T) {
 				nil,
 				true,
 			},
+			{
+				`${substr("foo", -4, -1)}`,
+				nil,
+				true,
+			},
 
 			// invalid length
 			{
-Original file line number
+Diff line change
@@ Expand Up / @@ -2568,6 +2568,11 @@ func TestInterpolateFuncSubstr(t *testing.T) { @@
     				nil,
     				true,
     			},
+    			{
+    				`${substr("foo", -4, -1)}`,
+    				nil,
+    				true,
+    			},
     			// invalid length
     			{
@@ Expand Down @@