Fix block_open handling in deflate_quick()

The attached test fails with "inflate() failed", because the deflate
stream that it produces ends up being corrupted. Bisect points to the
commit e7bb6db09a18 ("Replace hash_bits, hash_size and hash_mask with
defines."), but it's most likely a coincidence.

In any case, the reason is that if we happen to simultaneously exhaust
all the buffers (in, out and bi), we return finish_started without
writing the end of block symbol, which will never happen afterwards.

Fix by adding another check to the tricky condition: if we are in the
middle of a block, return need_more instead of finish_started.

3 files changed, 117 insertions, 1 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6cfd64f..45164fa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1283,6 +1283,12 @@ if(ZLIB_ENABLE_TESTS)
     target_link_libraries(deflate_quick_bi_valid zlib)
     set(DEFLATE_QUICK_BI_VALID_COMMAND ${CMAKE_CROSSCOMPILING_EMULATOR} $<TARGET_FILE:deflate_quick_bi_valid>)
     add_test(NAME deflate_quick_bi_valid COMMAND ${DEFLATE_QUICK_BI_VALID_COMMAND})
+
+    add_executable(deflate_quick_block_open test/deflate_quick_block_open.c)
+    configure_test_executable(deflate_quick_block_open)
+    target_link_libraries(deflate_quick_block_open zlib)
+    set(DEFLATE_QUICK_BLOCK_OPEN_COMMAND ${CMAKE_CROSSCOMPILING_EMULATOR} $<TARGET_FILE:deflate_quick_block_open>)
+    add_test(NAME deflate_quick_block_open COMMAND ${DEFLATE_QUICK_BLOCK_OPEN_COMMAND})
 endif()
 
 FEATURE_SUMMARY(WHAT ALL INCLUDE_QUIET_PACKAGES)
diff --git a/deflate_quick.c b/deflate_quick.c
index d749b3a..b439743 100644
--- a/deflate_quick.c
+++ b/deflate_quick.c
@@ -65,7 +65,7 @@ Z_INTERNAL block_state deflate_quick(deflate_state *s, int flush) {
         if (UNLIKELY(s->pending + ((BIT_BUF_SIZE + 7) >> 3) >= s->pending_buf_size)) {
             flush_pending(s->strm);
             if (s->strm->avail_out == 0) {
-                return (last && s->strm->avail_in == 0 && s->bi_valid == 0) ? finish_started : need_more;
+                return (last && s->strm->avail_in == 0 && s->bi_valid == 0 && s->block_open == 0) ? finish_started : need_more;
             }
         }
 
diff --git a/test/deflate_quick_block_open.c b/test/deflate_quick_block_open.c
new file mode 100644
index 0000000..42a3c20
--- /dev/null
+++ b/test/deflate_quick_block_open.c
@@ -0,0 +1,110 @@
+/* Generated by fuzzing - test block_open handling in deflate_quick(). */
+
+#include "zbuild.h"
+#ifdef ZLIB_COMPAT
+#  include "zlib.h"
+#else
+#  include "zlib-ng.h"
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main() {
+    PREFIX3(stream) strm;
+
+    memset(&strm, 0, sizeof(strm));
+    int ret = PREFIX(deflateInit2)(&strm, 1, Z_DEFLATED, -15, 1, Z_FILTERED);
+    if (ret != Z_OK) {
+        fprintf(stderr, "deflateInit2() failed with code %d\n", ret);
+        return EXIT_FAILURE;
+    }
+
+    z_const unsigned char next_in[494] =
+            "\x1d\x1d\x00\x00\x00\x4a\x4a\x4a\xaf\xaf\xaf\xaf\x4a\x4a\x4a\x4a"
+            "\x3f\x3e\xaf\xff\xff\xff\x11\xff\xff\xff\xff\xdf\x00\x00\x00\x01"
+            "\x3f\x7d\x00\x50\x00\x00\xc8\x01\x2b\x60\xc8\x00\x24\x06\xff\xff"
+            "\x4a\x4e\x4a\x7d\xc8\x01\xf1\x2b\x28\xb2\xb2\x60\x25\xc8\x06\x00"
+            "\x00\x00\x31\x00\x01\xb2\xb2\xb2\xff\xff\xfd\xb2\xb2\x40\xff\x7d"
+            "\x3b\x34\x3e\xff\xff\x4a\x4a\x01\xf1\xff\x02\xff\x3f\xff\x02\xff"
+            "\xff\xff\xbf\x0a\xff\x00\x01\x3f\xb3\xff\x26\x00\x00\x13\x00\xc8"
+            "\x3e\x3e\x3e\x4a\x76\x4a\x4a\x2e\x7d\x3e\x3e\x3e\x3e\x1d\x1d\x1d"
+            "\xfe\xea\xef\x80\x01\x00\x00\x40\x00\x00\xba\x00\x06\xfa\xb9\x11"
+            "\xbf\x98\xee\x45\x7e\x04\x00\xff\xff\xff\x67\xc3\xc3\xc3\xc3\x00"
+            "\x1d\x1d\xe1\xe3\x00\xc3\x1d\x98\x1d\x1d\x1d\x1d\x1d\x00\x00\x00"
+            "\x02\x00\x00\x00\xe8\x00\x00\x1d\x1d\x1d\xfa\x1e\x12\xff\xff\xff"
+            "\x00\x01\xa7\xff\xff\xff\x1d\x1d\x1d\x63\xff\xff\xff\x1f\x00\x00"
+            "\x10\x40\x00\x00\xad\xff\xff\x3f\x51\x00\xf8\xff\xff\x8a\x01\x05"
+            "\x00\x00\x03\x00\x00\xff\x00\x00\x00\x05\x40\x1f\x08\x0a\x00\xff"
+            "\xff\x01\x00\x12\x00\x00\x01\x00\x3f\x40\x1d\x1d\x1d\x1d\x1d\x1d"
+            "\x21\x00\x1d\x00\x00\x00\xe4\x00\x00\x00\x07\x00\x00\xe6\xe6\x34"
+            "\xe6\xe6\xe6\xe6\xff\x2b\xee\x1d\x1d\x1d\x93\x1d\x1d\x1d\xee\x2b"
+            "\xee\x01\x81\x1d\x00\x00\x58\x00\x00\x01\x14\x00\x1b\x00\x00\x2c"
+            "\x00\x00\x00\xdb\x00\x45\x7e\x00\x00\x00\xfb\xbd\x00\x06\x21\xd3"
+            "\x00\xff\xff\xff\xff\xff\x00\x49\x49\xc9\x49\x3d\x00\x34\x01\x00"
+            "\x00\x6a\x2b\x00\x00\x50\x40\xf0\xf0\xf0\xf0\xa3\xa3\xa3\xa3\xf0"
+            "\xf0\x06\xfa\xa9\x01\x10\xbf\x98\x9d\x2b\xee\x2d\x21\x01\xdb\x00"
+            "\x45\x10\x00\x00\x7e\x00\x00\xe7\x00\xff\xff\x00\xf6\x00\x00\x00"
+            "\xf9\x00\x00\x00\x11\x00\x00\x00\xe2\x00\x00\x00\x2d\x00\x00\x00"
+            "\x2f\x00\x3f\x54\x1d\x1d\x1d\x4c\x4c\x4c\x4c\x2a\x4c\x4c\x10\xff"
+            "\xff\x1a\x00\x00\x01\xff\x00\xff\xf9\x00\x3f\x53\xcc\xcc\xcc\xcc"
+            "\x6e\x00\x00\x01\xf8\xff\xff\xff\x49\x04\x2c\x01\x00\x1d\x00\x07"
+            "\x01\xff\x00\x00\x00\xf8\xff\x09\x00\x27\x00\x08\x21\x1c\x00\x00"
+            "\x00\x00\x1d\x05\x00\x00\x00\x2c\x53\x3f\x00\x01\x00\x00\xe6\xff"
+            "\xff\xff\x6a\x2b\xee\xe6\x6a\x2b\xee\x2b\xee\xee\x2b\xee";
+    strm.next_in = next_in;
+    unsigned char next_out[1116];
+    strm.next_out = next_out;
+
+    strm.avail_in = sizeof(next_in);
+    while (1) {
+        strm.avail_out = next_out + sizeof(next_out) - strm.next_out;
+        if (strm.avail_out > 38)
+            strm.avail_out = 38;
+        ret = PREFIX(deflate)(&strm, Z_FINISH);
+        if (ret == Z_STREAM_END)
+            break;
+        if (ret != Z_OK) {
+            fprintf(stderr, "deflate() failed with code %d\n", ret);
+            return EXIT_FAILURE;
+        }
+    }
+    uint32_t compressed_size = strm.next_out - next_out;
+
+    ret = PREFIX(deflateEnd)(&strm);
+    if (ret != Z_OK) {
+        fprintf(stderr, "deflateEnd() failed with code %d\n", ret);
+        return EXIT_FAILURE;
+    }
+
+    memset(&strm, 0, sizeof(strm));
+    ret = PREFIX(inflateInit2)(&strm, -15);
+    if (ret != Z_OK) {
+        fprintf(stderr, "inflateInit2() failed with code %d\n", ret);
+        return EXIT_FAILURE;
+    }
+
+    strm.next_in = next_out;
+    strm.avail_in = compressed_size;
+    unsigned char uncompressed[sizeof(next_in)];
+    strm.next_out = uncompressed;
+    strm.avail_out = sizeof(uncompressed);
+
+    ret = PREFIX(inflate)(&strm, Z_NO_FLUSH);
+    if (ret != Z_STREAM_END) {
+        fprintf(stderr, "inflate() failed with code %d\n", ret);
+        return EXIT_FAILURE;
+    }
+
+    ret = PREFIX(inflateEnd)(&strm);
+    if (ret != Z_OK) {
+        fprintf(stderr, "inflateEnd() failed with code %d\n", ret);
+        return EXIT_FAILURE;
+    }
+
+    if (memcmp(uncompressed, next_in, sizeof(uncompressed)) != 0) {
+        fprintf(stderr, "Uncompressed data differs from the original\n");
+        return EXIT_FAILURE;
+    }
+}