add fuzzing tests

Using fuzzing tests from zig-std-lib-fuzzing project:
https://github.com/squeek502/zig-std-lib-fuzzing/tree/master/inputs/deflate

Pointed by squeek502 in issues #1, #2, #3, #4.

Fixes #3, #4

src/bit_reader.zig

@@ -103,7 +103,7 @@ pub fn BitReader(comptime ReaderType: type) type {
                 0 => { // `normal` read
                     try self.fill(n); // ensure that there are n bits in the buffer
                     const u: U = @truncate(self.bits); // get n bits
-                    self.shift(n); // advance buffer for n
+                    try self.shift(n); // advance buffer for n
                     return u;
                 },
                 (flag.peek) => { // no shift, leave bits in the buffer
@@ -112,13 +112,13 @@ pub fn BitReader(comptime ReaderType: type) type {
                 },
                 flag.buffered => { // no fill, assume that buffer has enought bits
                     const u: U = @truncate(self.bits);
-                    self.shift(n);
+                    try self.shift(n);
                     return u;
                 },
                 (flag.reverse) => { // same as 0 with bit reverse
                     try self.fill(n);
                     const u: U = @truncate(self.bits);
-                    self.shift(n);
+                    try self.shift(n);
                     return @bitReverse(u);
                 },
                 (flag.peek | flag.reverse) => {
@@ -127,7 +127,7 @@ pub fn BitReader(comptime ReaderType: type) type {
                 },
                 (flag.buffered | flag.reverse) => {
                     const u: U = @truncate(self.bits);
-                    self.shift(n);
+                    try self.shift(n);
                     return @bitReverse(u);
                 },
                 (flag.peek | flag.buffered) => {
@@ -151,13 +151,13 @@ pub fn BitReader(comptime ReaderType: type) type {
             }
             const mask: u16 = (@as(u16, 1) << n) - 1;
             const u: u16 = @as(u16, @truncate(self.bits)) & mask;
-            self.shift(n);
+            try self.shift(n);
             return u;
         }
 
         // Advance buffer for n bits.
-        pub inline fn shift(self: *Self, n: u6) void {
-            assert(n <= self.nbits);
+        pub inline fn shift(self: *Self, n: u6) !void {
+            if (n > self.nbits) return error.EndOfStream;
             self.bits >>= n;
             self.nbits -= n;
         }
@@ -166,7 +166,7 @@ pub fn BitReader(comptime ReaderType: type) type {
         pub inline fn skipBytes(self: *Self, n: u16) !void {
             for (0..n) |_| {
                 try self.fill(8);
-                self.shift(8);
+                try self.shift(8);
             }
         }
 
@@ -178,7 +178,7 @@ pub fn BitReader(comptime ReaderType: type) type {
         // Align stream to the byte boundary.
         pub inline fn alignToByte(self: *Self) void {
             const ab = self.alignBits();
-            if (ab > 0) self.shift(ab);
+            if (ab > 0) self.shift(ab) catch unreachable;
         }
 
         // Skip zero terminated string.
@@ -232,17 +232,17 @@ test "BitReader" {
 
     try testing.expect(try br.readF(u8, F.peek) == 0b0001_1110);
     try testing.expect(try br.readF(u9, F.peek) == 0b1_0001_1110);
-    br.shift(9);
+    try br.shift(9);
     try testing.expectEqual(@as(u8, 36), br.nbits);
     try testing.expectEqual(@as(u3, 4), br.alignBits());
 
     try testing.expect(try br.readF(u4, 0) == 0b0100);
     try testing.expectEqual(@as(u8, 32), br.nbits);
     try testing.expectEqual(@as(u3, 0), br.alignBits());
 
-    br.shift(1);
+    try br.shift(1);
     try testing.expectEqual(@as(u3, 7), br.alignBits());
-    br.shift(1);
+    try br.shift(1);
     try testing.expectEqual(@as(u3, 6), br.alignBits());
     br.alignToByte();
     try testing.expectEqual(@as(u3, 0), br.alignBits());
@@ -285,18 +285,18 @@ test "BitReader init" {
     var br = bitReader(fbs.reader());
 
     try testing.expectEqual(@as(u64, 0x08_07_06_05_04_03_02_01), br.bits);
-    br.shift(8);
+    try br.shift(8);
     try testing.expectEqual(@as(u64, 0x00_08_07_06_05_04_03_02), br.bits);
     try br.fill(60); // fill with 1 byte
     try testing.expectEqual(@as(u64, 0x01_08_07_06_05_04_03_02), br.bits);
-    br.shift(8 * 4 + 4);
+    try br.shift(8 * 4 + 4);
     try testing.expectEqual(@as(u64, 0x00_00_00_00_00_10_80_70), br.bits);
 
     try br.fill(60); // fill with 4 bytes (shift by 4)
     try testing.expectEqual(@as(u64, 0x00_50_40_30_20_10_80_70), br.bits);
     try testing.expectEqual(@as(u8, 8 * 7 + 4), br.nbits);
 
-    br.shift(@intCast(br.nbits)); // clear buffer
+    try br.shift(@intCast(br.nbits)); // clear buffer
     try br.fill(8); // refill with the rest of the bytes
     try testing.expectEqual(@as(u64, 0x00_00_00_00_00_08_07_06), br.bits);
 }

src/inflate.zig

@@ -123,7 +123,7 @@ pub fn Inflate(comptime container: Container, comptime ReaderType: type) type {
         }
 
         inline fn decodeLength(self: *Self, code: u8) !u16 {
-            assert(code <= 28);
+            if (code > 28) return error.CorruptInput;
             const ml = Token.matchLength(code);
             return if (ml.extra_bits == 0) // 0 - 5 extra bits
                 ml.base
@@ -132,7 +132,7 @@ pub fn Inflate(comptime container: Container, comptime ReaderType: type) type {
         }
 
         inline fn decodeDistance(self: *Self, code: u8) !u16 {
-            assert(code <= 29);
+            if (code > 29) return error.CorruptInput;
             const md = Token.matchDistance(code);
             return if (md.extra_bits == 0) // 0 - 13 extra bits
                 md.base
@@ -158,7 +158,7 @@ pub fn Inflate(comptime container: Container, comptime ReaderType: type) type {
             var pos: usize = 0;
             while (pos < hlit) {
                 const sym = cl_h.find(try self.bits.peekF(u7, F.reverse));
-                self.bits.shift(sym.code_bits);
+                try self.bits.shift(sym.code_bits);
                 pos += try self.dynamicCodeLength(sym.symbol, &lit_l, pos);
             }
 
@@ -167,7 +167,7 @@ pub fn Inflate(comptime container: Container, comptime ReaderType: type) type {
             pos = 0;
             while (pos < hdist) {
                 const sym = cl_h.find(try self.bits.peekF(u7, F.reverse));
-                self.bits.shift(sym.code_bits);
+                try self.bits.shift(sym.code_bits);
                 pos += try self.dynamicCodeLength(sym.symbol, &dst_l, pos);
             }
 
@@ -234,7 +234,7 @@ pub fn Inflate(comptime container: Container, comptime ReaderType: type) type {
         inline fn decodeSymbol(self: *Self, decoder: anytype) !hfd.Symbol {
             const sym = decoder.find(try self.bits.peekF(u15, F.buffered | F.reverse));
             if (sym.code_bits == 0) return error.CorruptInput;
-            self.bits.shift(sym.code_bits);
+            try self.bits.shift(sym.code_bits);
             return sym;
         }
 
@@ -474,21 +474,81 @@ test "zlib decompress" {
     }
 }
 
-test "lengths overflow" {
-    const data = "\xed\x1d$\xe9\xff\xff9\x0e";
-
-    var fb = std.io.fixedBufferStream(data);
-    var al = std.ArrayList(u8).init(testing.allocator);
-    defer al.deinit();
-
-    try testing.expectError(error.CorruptInput, decompress(.raw, fb.reader(), al.writer()));
-}
+test "fuzzing tests" {
+    const cases = [_]struct {
+        in: []const u8,
+        out: []const u8 = "",
+        err: ?anyerror = null,
+    }{
+        .{ .in = @embedFile("testdata/fuzzing/deflate-stream"), .out =
+        \\[
+        \\    { id: "brieflz",
+        \\      name: "BriefLZ",
+        \\      libraryUrl: "https://github.com/jibsen/brieflz",
+        \\      license: "MIT",
+        \\      revision: "bcaa6a1ee7ccf005512b5c23aa92b40cf75f9ed1",
+        \\      codecs: [ { name: "brieflz" } ], },
+        \\    { id: "brotli",
+        \\      name: "Brotli",
+        \\      libraryUrl: "https://github.com/google/brotli",
+        \\      license: "Apache 2.0",
+        \\      revision: "1dd66ef114fd244778d9dcb5da09c28b49a0df33",
+        \\      codecs: [ { name: "brotli",
+        \\		  levels: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
+        \\		  streaming: true } ], },
+        \\    { id: "bsc",
+        \\      name: "bsc",
+        \\      libraryUrl: "http://libbsc.com/",
+        \\      license: "Apache 2.0",
+        \\      revision: "b2b07421381b19b2fada8b291f3cdead10578abc",
+        \\      codecs: [ { name: "bsc" } ] }
+        \\]
+        \\
+        },
+        .{ .in = @embedFile("testdata/fuzzing/empty-distance-alphabet01"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/empty-distance-alphabet02"), .out = "" },
+        .{ .in = @embedFile("testdata/fuzzing/end-of-stream"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/invalid-distance"), .err = error.EndOfStream }, // panic
+        .{ .in = @embedFile("testdata/fuzzing/invalid-tree01"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/invalid-tree02"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/invalid-tree03"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/lengths-overflow"), .err = error.CorruptInput },
+        //.{ .in = "\xed\x1d$\xe9\xff\xff9\x0e", .err = error.CorruptInput },
+
+        .{ .in = @embedFile("testdata/fuzzing/out-of-codes"), .err = error.CorruptInput },
+        //.{ .in = "\x950\x00\x0000000", .err = error.CorruptInput },
+        .{ .in = @embedFile("testdata/fuzzing/puff01"), .err = error.DeflateWrongNlen },
+        .{ .in = @embedFile("testdata/fuzzing/puff02"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/puff03"), .out = &[_]u8{0xa} },
+        .{ .in = @embedFile("testdata/fuzzing/puff04"), .err = error.CorruptInput }, // this was panicking
+        .{ .in = @embedFile("testdata/fuzzing/puff05"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/puff06"), .err = error.EndOfStream },
+        //.{ .in = @embedFile("testdata/fuzzing/puff07") }, // panic
+        .{ .in = @embedFile("testdata/fuzzing/puff08"), .err = error.CorruptInput },
+        //.{ .in = "\x04\xc0\x81\x08\x00\x00\x00\x00 \x7f\xeb\x0b\x00\x00", .err = error.CorruptInput },
+        .{ .in = @embedFile("testdata/fuzzing/puff09"), .out = "P" },
+        .{ .in = @embedFile("testdata/fuzzing/puff10"), .err = error.DeflateInvalidCode },
+        .{ .in = @embedFile("testdata/fuzzing/puff11"), .err = error.EndOfStream },
+
+        .{ .in = @embedFile("testdata/fuzzing/puff12"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/puff13"), .err = error.CorruptInput },
+        //.{ .in = "\x04\x00\xfe\xff", .err = error.CorruptInput },
+        .{ .in = @embedFile("testdata/fuzzing/puff14"), .err = error.CorruptInput },
+        .{ .in = @embedFile("testdata/fuzzing/puff15"), .err = error.EndOfStream },
+        .{ .in = @embedFile("testdata/fuzzing/puff16"), .err = error.EndOfStream }, // panic
+        .{ .in = @embedFile("testdata/fuzzing/puff17"), .err = error.EndOfStream },
+    };
 
-test "fix: infinite loop during 'out of codes'" {
-    const data = "\x950\x00\x0000000";
+    for (cases) |c| {
+        var fb = std.io.fixedBufferStream(c.in);
+        var al = std.ArrayList(u8).init(testing.allocator);
+        defer al.deinit();
 
-    var fb = std.io.fixedBufferStream(data);
-    var al = std.ArrayList(u8).init(testing.allocator);
-    defer al.deinit();
-    try testing.expectError(error.CorruptInput, decompress(.raw, fb.reader(), al.writer()));
+        if (c.err) |expected_err| {
+            try testing.expectError(expected_err, decompress(.raw, fb.reader(), al.writer()));
+        } else {
+            try decompress(.raw, fb.reader(), al.writer());
+            try testing.expectEqualStrings(c.out, al.items);
+        }
+    }
 }

src/testdata/fuzzing/deflate-stream

@@ -0,0 +1,3 @@
+��=o�0���+N������ڭR��K�}>W!AI@j+�{
+�|����<�����F�x[�ش�\�9f;P�%�0৷#��iu���V����UWDQ����L�YF��tTG�U���_�����|S�Q�D��<M�4)�Xk%M��e�SdűK�0�]Cas[v������;�ɕMSV����J�@N�5Ea�tJN��Y�$Y�[eѤVs�27��ܺ8���}wӆ��.H1��A�`� c�3PW���%��uY@߮�jN���]$
+,<���L�4<K��sa�2�i�s#�p1Z�V�4˵�����؎�o

src/testdata/fuzzing/end-of-stream

@@ -0,0 +1 @@
+��=o�0��0

src/testdata/fuzzing/invalid-tree01

@@ -0,0 +1 @@
+000

src/testdata/fuzzing/lengths-overflow

@@ -0,0 +1 @@
+�$���9

src/testdata/fuzzing/puff04

@@ -0,0 +1 @@
+~��

src/testdata/fuzzing/puff05

@@ -0,0 +1 @@
+

src/testdata/fuzzing/puff06

@@ -0,0 +1 @@
+�I�$I�$����

src/testdata/fuzzing/puff10

@@ -0,0 +1 @@
+

src/testdata/fuzzing/puff15

@@ -0,0 +1 @@
+�I�$I�$���Ä