feat: add fetch message size limit

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>
2026-09-26 08:43:32 -04:00
parent 681a66862e
commit 025812fe4e
4 changed files with 145 additions and 9 deletions
@@ -84,8 +84,15 @@ final class FetchOptions
        return $this->with('BODYSTRUCTURE');
    }

-    public function withBodyText(): self
+    /**
+     * @param int|null $limit Maximum number of octets to fetch (partial fetch `<0.limit>`), null for all
+     */
+    public function withBodyText(?int $limit = null): self
    {
+        if ($limit !== null && $limit > 0) {
+            return $this->with(sprintf('BODY.PEEK[TEXT]<0.%d>', $limit));
+        }
+
        return $this->with('BODY.PEEK[TEXT]');
    }

@@ -102,7 +102,14 @@ final class FetchMessageParser
                    $depth--;
                    if ($depth === 0) {
                        $offset++;
-                        return substr($payload, $start, $offset - $start);
+                        $name = substr($payload, $start, $offset - $start);
+
+                        // partial fetch responses carry the origin octet, e.g. BODY[TEXT]<0>
+                        if (preg_match('/\G<\d+>/A', $payload, $originMatches, 0, $offset) === 1) {
+                            $offset += strlen($originMatches[0]);
+                        }
+
+                        return $name;
                    }
                }

@@ -599,13 +606,15 @@ final class FetchMessageParser
            }

            $sections = [];
-            $segments = self::splitMultipartBody($content, $boundary);
+            $segments = self::splitMultipartBody($content, $boundary, $truncated);
+            $lastIndex = count($segments) - 1;
            foreach ($part->parts() as $index => $childPart) {
                if (!isset($segments[$index])) {
                    break;
                }

-                foreach (self::sectionsFromMimeEntity($segments[$index], $childPart) as $section => $childContent) {
+                $segmentTruncated = $truncated && $index === $lastIndex;
+                foreach (self::sectionsFromMimeEntity($segments[$index], $childPart, $segmentTruncated) as $section => $childContent) {
                    $sections[$section] = $childContent;
                }
            }
@@ -623,8 +632,13 @@ final class FetchMessageParser
    /**
     * @return array<string, string>
     */
-    private static function sectionsFromMimeEntity(string $content, MessagePart $part): array
+    private static function sectionsFromMimeEntity(string $content, MessagePart $part, bool $truncated = false): array
    {
+        // a truncated entity cut off inside its headers has no usable body
+        if ($truncated && !str_contains($content, "\r\n\r\n") && !str_contains($content, "\n\n")) {
+            return [];
+        }
+
        [, $body] = self::splitMimeEntity($content);

        if ($part->isMultipart()) {
@@ -655,10 +669,16 @@ final class FetchMessageParser
    }

    /**
+     * Split a multipart body into its entities.
+     *
+     * A body without a closing boundary (partial fetch or malformed message) keeps
+     * its last, unterminated entity and reports it through $truncated.
+     *
     * @return list<string>
     */
-    private static function splitMultipartBody(string $content, string $boundary): array
+    private static function splitMultipartBody(string $content, string $boundary, ?bool &$truncated = null): array
    {
+        $truncated = false;
        $pattern = '/(?:^|\r\n|\n)--' . preg_quote($boundary, '/') . '(--)?[ \t]*(?:\r\n|\n|$)/';
        if (preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE) < 1) {
            return [];
@@ -677,12 +697,17 @@ final class FetchMessageParser
                && $matches[1][$index][0] === '--';

            if ($isClosing) {
-                break;
+                return $segments;
            }

            $segmentStart = $offset + strlen($match);
        }

+        if ($segmentStart !== null && $segmentStart < strlen($content)) {
+            $segments[] = substr($content, $segmentStart);
+            $truncated = true;
+        }
+
        return $segments;
    }

@@ -706,11 +731,22 @@ final class FetchMessageParser
        return ['', $content];
    }

+    /**
+     * Decode base64 content, ignoring an incomplete trailing quantum left by a partial fetch.
+     */
+    private static function decodeBase64(string $content): string
+    {
+        $content = preg_replace('/[^A-Za-z0-9+\/=]/', '', $content) ?? '';
+        $content = substr($content, 0, strlen($content) - (strlen($content) % 4));
+
+        return base64_decode($content, true) ?: '';
+    }
+
    private static function decodeSectionContent(string $content, ?string $encoding, string $charset): string
    {
        $decoded = match (strtolower($encoding ?? '7bit')) {
            'quoted-printable' => quoted_printable_decode($content),
-            'base64' => base64_decode($content, true) ?: '',
+            'base64' => self::decodeBase64($content),
            default => $content,
        };

@@ -61,6 +61,7 @@ class RemoteMailService

    private const COLLECTION_FILTER_OPTIONS = ['name', 'role', 'subscription'];
    private const DEFAULT_MAILBOX_STATUS_ITEMS = ['MESSAGES', 'UNSEEN', 'RECENT', 'UIDNEXT', 'UIDVALIDITY'];
+    private const LIST_BODY_TEXT_LIMIT = 1048576; // 1 MB

    private ?ImapClient $imapClient = null;
    private ?SmtpClient $smtpClient = null;
@@ -304,7 +305,8 @@ class RemoteMailService
     */
    public function entityList(string $collection, ?IFilter $filter = null, ?ISort $sort = null, ?IRange $range = null): Generator
    {
-        $options = FetchOptions::message()->withBodyText();
+        // text parts normally precede attachments, so capping TEXT avoids transferring attachment bytes
+        $options = FetchOptions::message()->withBodyText(self::LIST_BODY_TEXT_LIMIT);

        // fast path: fetch all messages without filtering, sorting or pagination
        if ($filter === null && $sort === null && $range === null) {