Move Downloader into its own file.

batch/makedist.sh

@@ -144,6 +144,7 @@ lib/dbhelper.sh
 lib/dbl.php
 lib/diff_match_patch.php
 lib/dkimsigner.php
+lib/downloader.php
 lib/filer.php
 lib/fmt.php
 lib/ftext.php

lib/csv.php

@@ -1,6 +1,6 @@
 <?php
 // csv.php -- HotCRP CSV parsing functions
-// Copyright (c) 2006-2023 Eddie Kohler; see LICENSE.
+// Copyright (c) 2006-2024 Eddie Kohler; see LICENSE.
 
 class CsvRow implements ArrayAccess, IteratorAggregate, Countable, JsonSerializable {
     /** @var list<string> */
@@ -939,7 +939,7 @@ function flush() {
             if (($this->flags & self::FLAG_COMPLETING) === 0) {
                 // signal to NGINX that buffering is a waste of time
                 header("X-Accel-Buffering: no");
-            } else if (!Filer::skip_content_length_header()) {
+            } else if (!Downloader::skip_content_length_header()) {
                 header("Content-Length: " . (strlen($this->headerline) + $this->lines_length));
             }
         }

lib/downloader.php

@@ -0,0 +1,327 @@
+<?php
+// downloader.php -- download helper class
+// Copyright (c) 2006-2024 Eddie Kohler; see LICENSE.
+
+class Downloader {
+    /** @var ?string */
+    public $etag;
+    /** @var ?int */
+    public $content_length;
+    /** @var ?string */
+    public $mimetype;
+
+    /** @var ?string */
+    public $if_match;
+    /** @var ?string */
+    public $if_none_match;
+    /** @var ?string */
+    public $if_range;
+    /** @var ?list<array{int,int}> */
+    public $range;
+    /** @var bool */
+    public $head = false;
+    /** @var ?bool */
+    public $attachment;
+    /** @var bool */
+    public $single = false;
+    /** @var bool */
+    public $cacheable = false;
+    /** @var bool */
+    public $no_accel = false;
+    /** @var ?Contact */
+    public $log_user;
+
+    /** @return Downloader */
+    static function make_server_request() {
+        $dopt = new Downloader;
+        $dopt->if_match = $_SERVER["HTTP_IF_MATCH"] ?? null;
+        $dopt->if_none_match = $_SERVER["HTTP_IF_NONE_MATCH"] ?? null;
+        $method = $_SERVER["REQUEST_METHOD"];
+        if ($method === "HEAD") {
+            $dopt->head = true;
+        } else if ($method === "GET") {
+            $dopt->if_range = $_SERVER["HTTP_IF_RANGE"] ?? null;
+        }
+        if ($method === "GET"
+            && ($range = $_SERVER["HTTP_RANGE"] ?? null) !== null
+            && preg_match('/\Abytes\s*=\s*(?:(?:\d+-\d+|-\d+|\d+-)\s*,?\s*)+\z/', $range)) {
+            $dopt->range = [];
+            $lastr = null;
+            preg_match_all('/\d+-\d+|-\d+|\d+-/', $range, $m);
+            foreach ($m[0] as $t) {
+                $dash = strpos($t, "-");
+                $r1 = $dash === 0 ? null : intval(substr($t, 0, $dash));
+                $r2 = $dash === strlen($t) - 1 ? null : intval(substr($t, $dash + 1));
+                if ($r1 === null && $r2 !== 0) {
+                    $dopt->range[] = $lastr = [$r1, $r2];
+                } else if ($r2 === null || ($r1 !== null && $r1 <= $r2)) {
+                    if ($lastr !== null
+                        && $lastr[0] !== null
+                        && $lastr[1] !== null
+                        && $r1 >= $lastr[0]
+                        && $r1 - $lastr[1] <= 100) {
+                        $nr = count($dopt->range);
+                        $dopt->range[$nr - 1][1] = $lastr[1] = $r2;
+                    } else {
+                        $dopt->range[] = $lastr = [$r1, $r2];
+                    }
+                } else {
+                    $dopt->range = null;
+                    break;
+                }
+            }
+        }
+        return $dopt;
+    }
+
+    /** @param ?string $e1
+     * @param ?string $e2
+     * @param bool $strong
+     * @return bool */
+    static function etag_equals($e1, $e2, $strong) {
+        if ($e1 === null || $e2 === null) {
+            return false;
+        }
+        $w1 = str_starts_with($e1, "W/");
+        $w2 = str_starts_with($e2, "W/");
+        return (!$w1 || !$w2 || !$strong)
+            && ($w1 ? substr($e1, 2) : $e1) === ($w2 ? substr($e2, 2) : $e2);
+    }
+
+    /** @param string $s
+     * @param bool $strong */
+    private function any_etag_match($s, $strong) {
+        $pos = 0;
+        while (preg_match('/\G[,\s]*((?:W\/|)".*?"|\*)/', $s, $m, 0, $pos)) {
+            if ($m[1] === "*" || self::etag_equals($m[1], $this->etag, $strong)) {
+                return true;
+            }
+            $pos += strlen($m[1]);
+        }
+        return false;
+    }
+
+    /** @return bool */
+    function run_match() {
+        if ($this->etag === null) {
+            return false;
+        } else if ($this->if_match !== null
+                   && !$this->any_etag_match($this->if_match, true)) {
+            header("HTTP/1.1 412 Precondition Failed");
+            header("ETag: {$this->etag}");
+            return true;
+        } else if ($this->if_none_match !== null
+                   && $this->any_etag_match($this->if_none_match, false)) {
+            header("HTTP/1.1 304 Not Modified");
+            header("ETag: {$this->etag}");
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /** @param int $first
+     * @param int $last
+     * @return bool */
+    function range_overlaps($first, $last) {
+        assert($first < $last);
+        $length = $this->content_length ?? ($first + 1);
+        foreach ($this->range ?? [[0, null]] as $r) {
+            $r1 = $r[0] ?? 0;
+            $r2 = $r[1] ?? ($length - 1);
+            if ($last > $r1 && $first < $r2 + 1) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /** @return bool */
+    function run_range_check() {
+        assert($this->content_length !== null);
+        $filesize = $this->content_length;
+        if ($this->if_range !== null
+            && !self::etag_equals($this->if_range, $this->etag, true)) {
+            $this->range = null;
+        }
+        if ($this->range !== null) {
+            $rs = [];
+            foreach ($this->range as $r) {
+                list($r0, $r1) = $r;
+                if ($r0 === null) {
+                    $r0 = max($filesize - $r1, 0);
+                    $r1 = $filesize;
+                } else if ($r1 === null) {
+                    $r1 = $filesize;
+                } else {
+                    $r1 = min($filesize, $r1 + 1);
+                }
+                if ($r0 < $r1) {
+                    $rs[] = [$r0, $r1];
+                }
+            }
+            if (empty($rs)) {
+                header("HTTP/1.1 416 Range Not Satisfiable");
+                header("Content-Range: bytes */{$filesize}");
+                return true;
+            }
+            $this->range = $rs;
+        }
+        return false;
+    }
+
+    /** @return Generator<array{int,int}> */
+    function run_output_ranges() {
+        assert($this->content_length !== null && $this->mimetype !== null);
+        if ($this->etag !== null) {
+            header("ETag: {$this->etag}");
+        }
+        $range = $this->range;
+        $rangeheader = [];
+        $clen = $this->content_length;
+        if ($this->head) {
+            header("HTTP/1.1 204 No Content");
+            header("Content-Type: {$this->mimetype}");
+            header("Content-Length: {$clen}");
+            header("Accept-Ranges: bytes");
+            return;
+        } else if (!isset($range)) {
+            $outsize = $clen;
+            header("Content-Type: {$this->mimetype}");
+            header("Accept-Ranges: bytes");
+        } else if (count($range) === 1) {
+            $outsize = $range[0][1] - $range[0][0];
+            header("HTTP/1.1 206 Partial Content");
+            header("Content-Type: {$this->mimetype}");
+            header("Content-Range: bytes {$range[0][0]}-" . ($range[0][1] - 1) . "/{$clen}");
+        } else {
+            $boundary = "HotCRP-" . base64_encode(random_bytes(18));
+            $outsize = 0;
+            foreach ($range as $r) {
+                $rangeheader[] = "--{$boundary}\r\nContent-Type: {$this->mimetype}\r\nContent-Range: bytes {$r[0]}-" . ($r[1] - 1) . "/{$clen}\r\n\r\n";
+                $outsize += $r[1] - $r[0];
+            }
+            $rangeheader[] = "--{$boundary}--\r\n";
+            header("HTTP/1.1 206 Partial Content");
+            header("Content-Type: multipart/byteranges; boundary={$boundary}");
+            $outsize += strlen(join("", $rangeheader));
+        }
+        if (!self::skip_content_length_header()) {
+            header("Content-Length: {$outsize}");
+        }
+        if ($outsize > 2000000) {
+            header("X-Accel-Buffering: no");
+        }
+        flush();
+        while (@ob_end_flush()) {
+            // do nothing
+        }
+        if (!isset($range)) {
+            yield [0, $clen];
+        } else if (count($range) === 1) {
+            yield [$range[0][0], $range[0][1]];
+        } else {
+            for ($i = 0; $i !== count($range); ++$i) {
+                echo $rangeheader[$i];
+                yield [$range[$i][0], $range[$i][1]];
+            }
+            echo $rangeheader[count($range)];
+        }
+    }
+
+    /** @param string $filename */
+    function output_file($filename) {
+        // if docstoreAccelRedirect, output X-Accel-Redirect header
+        // XXX Chromium issue 961617: beware of X-Accel-Redirect if you are
+        // using SameSite cookies!
+        $this->content_length = filesize($filename);
+        if ($this->run_range_check()) {
+            return;
+        }
+        if (($dar = Conf::$main->opt("docstoreAccelRedirect"))
+            && ($dsp = Filer::docstore_fixed_prefix(Conf::$main->docstore()))
+            && !$this->no_accel
+            && !$this->head) {
+            assert(str_ends_with($dsp, "/"));
+            if (str_starts_with($filename, $dsp)
+                && strlen($filename) > strlen($dsp)
+                && $filename[strlen($dsp)] !== "/") {
+                if (isset($this->etag)) {
+                    header("ETag: {$this->etag}");
+                }
+                header("Content-Type: {$this->mimetype}");
+                header("X-Accel-Redirect: {$dar}" . substr($filename, strlen($dsp)));
+                return;
+            }
+        }
+        // write length header, flush output buffers
+        $out = fopen("php://output", "wb");
+        foreach ($this->run_output_ranges() as $r) {
+            self::readfile_subrange($out, $r[0], $r[1], 0, $filename, $this->content_length);
+        }
+    }
+
+    /** @param string $s */
+    function output_string($s) {
+        $this->content_length = strlen($s);
+        if ($this->run_range_check()) {
+            return;
+        }
+        $out = fopen("php://output", "wb");
+        foreach ($this->run_output_ranges() as $r) {
+            self::print_subrange($out, $r[0], $r[1], 0, $s);
+        }
+    }
+
+
+    // range handling
+    /** @param resource $out
+     * @param int $r0 - start of desired range
+     * @param int $r1 - end of desired range
+     * @param int $p0 - start of object
+     * @param string $s - object
+     * @return int */
+    static function print_subrange($out, $r0, $r1, $p0, $s) {
+        $sz = strlen($s);
+        $p1 = $p0 + $sz;
+        if ($p1 <= $r0 || $r1 <= $p0 || $p0 === $p1) {
+            return $sz;
+        } else if ($r0 <= $p0 && $p1 <= $r1) {
+            return fwrite($out, $s);
+        } else {
+            $off = max(0, $r0 - $p0);
+            $len = min($sz, $r1 - $p0) - $off;
+            return $off + fwrite($out, substr($s, $off, $len));
+        }
+    }
+
+    /** @param resource $out
+     * @param int $r0 - start of desired range
+     * @param int $r1 - end of desired range
+     * @param int $p0 - start of object
+     * @param string $fn - object
+     * @param int $sz - length of object
+     * @return int */
+    static function readfile_subrange($out, $r0, $r1, $p0, $fn, $sz) {
+        $p1 = $p0 + $sz; // - end of object
+        if ($p1 <= $r0 || $r1 <= $p0 || $p0 === $p1) {
+            return $sz;
+        } else if ($r0 <= $p0 && $p1 <= $r1 && $sz < 20000000) {
+            return readfile($fn);
+        } else if (($f = fopen($fn, "rb"))) {
+            $off = max(0, $r0 - $p0);
+            $len = min($sz, $r1 - $p0) - $off;
+            $off += stream_copy_to_stream($f, $out, $len, $off);
+            fclose($f);
+            return $off;
+        } else {
+            return 0;
+        }
+    }
+
+    /** @return bool */
+    static function skip_content_length_header() {
+        // see also Cacheable_Page::skip_content_length_header
+        return zlib_get_coding_type() !== false;
+    }
+}