Fix #75776: Flushing streams with compression filter is broken

First, the `bzip2.compress` filter has the same issue as `zlib.deflate`
so we port the respective fix[1] to ext/bz2.

Second, there is still an issue, if a stream with an attached
compression filter is flushed before it is closed, without any writes
in between.  In that case, the compression is never finalized.  We fix
this by enforcing a `_php_stream_flush()` with the `closing` flag set
in `_php_stream_free()`, whenever a write filter is attached.  This
call is superfluous for most write filters, but does not hurt, even
when it is unnecessary.

[1] <http://git.php.net/?p=php-src.git;a=commit;h=20e75329f2adb11dd231852c061926d0e4080929>

Closes GH-6703.

2 files changed, 34 insertions, 3 deletions

diff --git a/ext/bz2/bz2_filter.c b/ext/bz2/bz2_filter.c
index e7d7c3334f..fb79cb5dc6 100644
--- a/ext/bz2/bz2_filter.c
+++ b/ext/bz2/bz2_filter.c
@@ -41,6 +41,7 @@ typedef struct _php_bz2_filter_data {
 	enum strm_status status;              /* Decompress option */
 	unsigned int small_footprint : 1;     /* Decompress option */
 	unsigned int expect_concatenated : 1; /* Decompress option */
+	unsigned int is_flushed : 1;          /* only for compression */
 
 	int persistent;
 } php_bz2_filter_data;
@@ -228,6 +229,8 @@ static php_stream_filter_status_t php_bz2_compress_filter(
 		bucket = php_stream_bucket_make_writeable(buckets_in->head);
 
 		while (bin < bucket->buflen) {
+			int flush_mode;
+
 			desired = bucket->buflen - bin;
 			if (desired > data->inbuf_len) {
 				desired = data->inbuf_len;
@@ -235,7 +238,9 @@ static php_stream_filter_status_t php_bz2_compress_filter(
 			memcpy(data->strm.next_in, bucket->buf + bin, desired);
 			data->strm.avail_in = desired;
 
-			status = BZ2_bzCompress(&(data->strm), flags & PSFS_FLAG_FLUSH_CLOSE ? BZ_FINISH : (flags & PSFS_FLAG_FLUSH_INC ? BZ_FLUSH : BZ_RUN));
+			flush_mode = flags & PSFS_FLAG_FLUSH_CLOSE ? BZ_FINISH : (flags & PSFS_FLAG_FLUSH_INC ? BZ_FLUSH : BZ_RUN);
+			data->is_flushed = flush_mode != BZ_RUN;
+			status = BZ2_bzCompress(&(data->strm), flush_mode);
 			if (status != BZ_RUN_OK && status != BZ_FLUSH_OK && status != BZ_FINISH_OK) {
 				/* Something bad happened */
 				php_stream_bucket_delref(bucket);
@@ -261,11 +266,12 @@ static php_stream_filter_status_t php_bz2_compress_filter(
 		php_stream_bucket_delref(bucket);
 	}
 
-	if (flags & PSFS_FLAG_FLUSH_CLOSE) {
+	if (flags & PSFS_FLAG_FLUSH_CLOSE || ((flags & PSFS_FLAG_FLUSH_INC) && !data->is_flushed)) {
 		/* Spit it out! */
 		status = BZ_FINISH_OK;
 		while (status == BZ_FINISH_OK) {
-			status = BZ2_bzCompress(&(data->strm), BZ_FINISH);
+			status = BZ2_bzCompress(&(data->strm), (flags & PSFS_FLAG_FLUSH_CLOSE ? BZ_FINISH : BZ_FLUSH));
+			data->is_flushed = 1;
 			if (data->strm.avail_out < data->outbuf_len) {
 				size_t bucketlen = data->outbuf_len - data->strm.avail_out;
 
@@ -381,6 +387,7 @@ static php_stream_filter *php_bz2_filter_create(const char *filtername, zval *fi
 		}
 
 		status = BZ2_bzCompressInit(&(data->strm), blockSize100k, 0, workFactor);
+		data->is_flushed = 1;
 		fops = &php_bz2_compress_ops;
 	} else {
 		status = BZ_DATA_ERROR;
diff --git a/ext/bz2/tests/bug75776.phpt b/ext/bz2/tests/bug75776.phpt
new file mode 100644
index 0000000000..43cc6e07b5
--- /dev/null
+++ b/ext/bz2/tests/bug75776.phpt
@@ -0,0 +1,24 @@
+--TEST--
+Bug #75776 (Flushing streams with compression filter is broken)
+--SKIPIF--
+<?php
+if (!extension_loaded('bz2')) die('skip bz2 extension not available');
+?>
+--FILE--
+<?php
+$text = str_repeat('0123456789abcdef', 1000);
+
+$temp = fopen('php://temp', 'r+');
+stream_filter_append($temp, 'bzip2.compress', STREAM_FILTER_WRITE);
+fwrite($temp, $text);
+
+rewind($temp);
+
+var_dump(bin2hex(stream_get_contents($temp)));
+var_dump(ftell($temp));
+
+fclose($temp);
+?>
+--EXPECT--
+string(144) "425a68343141592653599fe7bbbf0001f389007fe03f002000902980026826aa80003ea9061520c6a41954833a9069520d6a41b54837a9071520e6a41d5483ba9079520f6a41f548"
+int(72)