Fix GH-16695: phar:// tar parser and zero-length file header blocks

There are two issues:
1) There's an off-by-one in the check for the minimum file size for a
   tar (i.e. `>` instead of `>=`).
2) The loop in the tar parsing parses a header, and then unconditionally
   reads the next one. However, that doesn't necessarily exist.
   Instead, we remove the loop condition and check for the end of the
   file before reading the next header. Note that we can't use
   php_stream_eof as the flag may not be set yet when we're already at
   the end.

Author: nielsdos

ext/phar/phar.c

@@ -1774,7 +1774,7 @@ static int phar_open_from_fp(php_stream* fp, char *fname, size_t fname_len, char
 				return phar_parse_zipfile(fp, fname, fname_len, alias, alias_len, pphar, error);
 			}
 
-			if (got > 512) {
+			if (got >= 512) {
 				if (phar_is_tar(pos, fname)) {
 					php_stream_rewind(fp);
 					return phar_parse_tarfile(fp, fname, fname_len, alias, alias_len, pphar, is_data, compression, error);

ext/phar/tar.c

@@ -254,9 +254,8 @@ int phar_parse_tarfile(php_stream* fp, char *fname, size_t fname_len, char *alia
 	entry.is_tar = 1;
 	entry.is_crc_checked = 1;
 	entry.phar = myphar;
-	pos += sizeof(buf);
 
-	do {
+	while (true) {
 		phar_entry_info *newentry;
 
 		pos = php_stream_tell(fp);
@@ -597,6 +596,11 @@ int phar_parse_tarfile(php_stream* fp, char *fname, size_t fname_len, char *alia
 			}
 		}
 
+		/* Only read next header if we're not yet at the end */
+		if (php_stream_tell(fp) == totalsize) {
+			break;
+		}
+
 		read = php_stream_read(fp, buf, sizeof(buf));
 
 		if (read != sizeof(buf)) {
@@ -607,7 +611,7 @@ int phar_parse_tarfile(php_stream* fp, char *fname, size_t fname_len, char *alia
 			phar_destroy_phar_data(myphar);
 			return FAILURE;
 		}
-	} while (!php_stream_eof(fp));
+	}
 
 	if (zend_hash_str_exists(&(myphar->manifest), ".phar/stub.php", sizeof(".phar/stub.php")-1)) {
 		myphar->is_data = 0;

ext/phar/tests/tar/gh16695_1.phpt

@@ -0,0 +1,28 @@
+--TEST--
+GH-16695 (phar:// tar parser and zero-length file header blocks)
+--CREDITS--
+hakre
+--EXTENSIONS--
+phar
+--INI--
+phar.require_hash=0
+--FILE--
+<?php
+
+$reportTar = __DIR__.'/gh16695_1.tmp';
+
+$length = file_put_contents($reportTar, base64_decode('dGxzAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAADAwMDA3MDAAMDAwMDAwMAAwMDAwMDAwADAwMDAwMDAwMDAwADAwMDAwMDAwMDAwADAwNzcxNgAgNQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAB1c3RhcgAwMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAwMDAwMDAwADAwMDAwMDAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA='));
+var_dump($length);
+$buffer = file_get_contents("phar://$reportTar/tls");
+var_dump($buffer);
+
+?>
+--CLEAN--
+<?php
+@unlink(__DIR__.'/gh16695_1.tmp');
+?>
+--EXPECTF--
+int(512)
+
+Warning: file_get_contents(%stls): Failed to open stream: phar error: path "tls" is a directory in %s on line %d
+bool(false)

ext/phar/tests/tar/gh16695_2.phpt

@@ -0,0 +1,26 @@
+--TEST--
+GH-16695 (phar:// tar parser and zero-length file header blocks)
+--CREDITS--
+hakre
+--EXTENSIONS--
+phar
+--INI--
+phar.require_hash=0
+--FILE--
+<?php
+
+$reportTar = __DIR__.'/gh16695_2.tmp';
+
+$length = file_put_contents($reportTar, base64_decode('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'));
+var_dump($length);
+$buffer = file_get_contents("phar://$reportTar/meta.json");
+var_dump($buffer);
+
+?>
+--CLEAN--
+<?php
+@unlink(__DIR__.'/gh16695_2.tmp');
+?>
+--EXPECT--
+int(1024)
+string(122) "{"Name":"default","Metadata":{},"Endpoints":{"docker":{"Host":"unix:///run/user/1000/docker.sock","SkipTLSVerify":false}}}"

ext/phar/tests/tar/gh16695_3.phpt

@@ -0,0 +1,26 @@
+--TEST--
+GH-16695 (phar:// tar parser and zero-length file header blocks)
+--CREDITS--
+hakre
+--EXTENSIONS--
+phar
+--INI--
+phar.require_hash=0
+--FILE--
+<?php
+
+$reportTar = __DIR__.'/gh16695_3.tmp';
+
+$length = file_put_contents($reportTar, base64_decode('dGxzAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAADAwMDA3MDAAMDAwMDAwMAAwMDAwMDAwADAwMDAwMDAwMDAwADAwMDAwMDAwMDAwADAwNzcxMQAgMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAB1c3RhcgAwMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAwMDAwMDAwADAwMDAwMDAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA='));
+var_dump($length);
+$buffer = file_get_contents("phar://$reportTar/tls");
+var_dump($buffer);
+
+?>
+--CLEAN--
+<?php
+@unlink(__DIR__.'/gh16695_3.tmp');
+?>
+--EXPECT--
+int(512)
+string(0) ""