Fix a crash from attempted to read past the end of input when given i…

…ncomplete input data. Closes bignerdranch#199.
cbrauchli · Sep 13, 2016 · 6703a48 · 6703a48
1 parent a3192bf
commit 6703a48
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Showing 2 changed files with 19 additions and 2 deletions.
diff --git a/Sources/JSONParser.swift b/Sources/JSONParser.swift
@@ -158,8 +158,12 @@ public struct JSONParser {
                 return try decodeNumberAsString(start)
             }
         }
-
-        throw Error.ValueInvalid(offset: loc, character: UnicodeScalar(input[loc]))
+
+        if loc < input.count {
+            throw Error.ValueInvalid(offset: loc, character: UnicodeScalar(input[loc]))
+        } else {
+            throw Error.EndOfStreamUnexpected
+        }
     }
 
     private mutating func skipWhitespace() {

diff --git a/Tests/JSONParserTests.swift b/Tests/JSONParserTests.swift
@@ -153,6 +153,19 @@ class JSONParserTests: XCTestCase {
         XCTAssertEqual(value, JSON.String(expect))
     }
 
+    func testThatParserFailsWhenIncompleteDataIsPresent() {
+        for s in [" ", "[0,", "{\"\":"] {
+            do {
+                let value = try JSONFromString(" ")
+                XCTFail("Unexpectedly parsed \(s) as \(value)")
+            } catch JSONParser.Error.EndOfStreamUnexpected {
+                // expected error - do nothing
+            } catch {
+                XCTFail("Unexpected error \(error)")
+            }
+        }
+    }
+
     func testThatParserUnderstandsNumbers() {
         for (string, shouldBeInt) in [
             ("  0  ", 0),