From 4de2cf34e6c1bbb4037d08d630ea665ecdce10c4 Mon Sep 17 00:00:00 2001
From: Justine Tunney <jtunney@gmail.com>
Date: Mon, 7 Nov 2022 05:52:24 -0800
Subject: [PATCH] Allow HTTP range past EOF

Fixes #683
---
 net/http/parsehttprange.c           |  5 ++++-
 test/net/http/parsehttprange_test.c | 20 ++++++++++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/net/http/parsehttprange.c b/net/http/parsehttprange.c
index 869e909fd..76c9f5db9 100644
--- a/net/http/parsehttprange.c
+++ b/net/http/parsehttprange.c
@@ -77,8 +77,11 @@ bool ParseHttpRange(const char *p, size_t n, long resourcelength,
   if (n) return false;
   if (start < 0) return false;
   if (length < 1) return false;
+  if (start > resourcelength) return false;
   if (__builtin_add_overflow(start, length, &ending)) return false;
-  if (ending > resourcelength) return false;
+  if (ending > resourcelength) {
+    length = resourcelength - start;
+  }
   *out_start = start;
   *out_length = length;
   return true;
diff --git a/test/net/http/parsehttprange_test.c b/test/net/http/parsehttprange_test.c
index 6a3f7e323..299a2f5a1 100644
--- a/test/net/http/parsehttprange_test.c
+++ b/test/net/http/parsehttprange_test.c
@@ -46,7 +46,11 @@ TEST(ParseHttpRange, testEmptyRangeOfOneByteFile_itWorks) {
 
 TEST(ParseHttpRange, testEmptyRangeOfEmptyFile_outOfRange) {
   long start, length;
-  const char *s = "bytes=0-0";
+  const char *s = "bytes=0-0";  // requesting 1 byte, but have 0
+  EXPECT_TRUE(ParseHttpRange(s, strlen(s), 0, &start, &length));
+  EXPECT_EQ(0, start);
+  EXPECT_EQ(0, length);
+  s = "bytes=1-1";  // but this can't be truncated
   EXPECT_FALSE(ParseHttpRange(s, strlen(s), 0, &start, &length));
   EXPECT_EQ(0, start);
   EXPECT_EQ(0, length);
@@ -94,10 +98,10 @@ TEST(ParseHttpRange, testFromEnd) {
 
 TEST(ParseHttpRange, testOutOfRange) {
   long start, length;
-  const char *s = "bytes=0-100";
-  EXPECT_FALSE(ParseHttpRange(s, strlen(s), 100, &start, &length));
+  const char *s = "bytes=0-100";  // requesting 101 bytes, but have 100
+  EXPECT_TRUE(ParseHttpRange(s, strlen(s), 100, &start, &length));
   EXPECT_EQ(0, start);
-  EXPECT_EQ(0, length);
+  EXPECT_EQ(100, length);
 }
 
 TEST(ParseHttpRange, testInvalidRange) {
@@ -131,3 +135,11 @@ TEST(ParseHttpRange, testMultipartRange_notImplemented) {
   EXPECT_EQ(0, start);
   EXPECT_EQ(0, length);
 }
+
+TEST(ParseHttpRange, rangeTooLong_shortensToActualLength) {
+  long start, length;
+  const char *s = "bytes=0-134217727";
+  EXPECT_TRUE(ParseHttpRange(s, strlen(s), 1000, &start, &length));
+  EXPECT_EQ(0, start);
+  EXPECT_EQ(1000, length);
+}