创建 MIME 边界的规则（对于邮件附件）

发布于 2024-11-10 05:27:59 字数 487 浏览 0 评论 0原文

我正在使用 PHP mail() 函数发送带有附件的邮件。因此，PHP 源内容包含一个边界来定义附件的开始和结束位置。

所以问题是：创建这个 MIME 边界有什么规则吗（例如只允许使用字母和数字）我仍然知道这个问题 -> 哪些规则适用于 MIME 边界？是否有必要为 HASH 创建边界？因为以下内容也适用：

$headers .= "Content-Type: multipart/related; boundary=\"abc\"";
[...]
$msg .="--abc\n";
[...]
$msg .= "--abc--\n\n";

是否有原因，为什么 MIME 边界应该是唯一的值？

..我在互联网上没有找到任何信息。

谢谢你！

原文

i'm using the PHP mail() function to send mails with attachment.
Therefore the PHP source contents an boundary to define where the attachment begins and ends.

So the question is: are there any ruels for creating this MIME boundary (exampt that are only letters and numbres are allowed)
i still know this SO question -> What rules apply to MIME boundary?
Is it necessary to create an boundary form an HASH?
Because the following also works:

$headers .= "Content-Type: multipart/related; boundary=\"abc\"";
[...]
$msg .="--abc\n";
[...]
$msg .= "--abc--\n\n";

Is there a reason, why a MIME boundary should be an unique value?

..i didn't found any information at the Internet.

Thank you!

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动次打次papapa 2024-11-17 05:27:59

没有什么规定边界标记必须是哈希值，但它们必须是唯一的。想象一下，如果您插入的实际电子邮件文本在某处自然包含单词 --abc-- ，会发生什么。

您的电子邮件看起来像这样：

--abc--    <--actual boundary
This is my email. There are many like it, but this one is mine.
Now for some reason I'm going to put in a line that shouldn't be there
--abc--    <--part of the email
There it was. Did you see it? No, you didn't, because the mail client saw a boundary
line and sliced it out. Because of this extra boundary, now the email has 2 sections,
instead of 1.
--abc--    <--actual boundary

那么...邮件客户端如何知道电子邮件的一部分以及“开销”是什么？这就是为什么你使用独特的边界。

哈希是最简单的方法。在极端情况下，电子邮件文本不太可能在可以被视为边界标记的确切位置包含自己的哈希值。

Nothing says the boundary markers have to be hashes, but they MUST be unique. Think of what would happen if the actual email text you're inserting naturally contains the words --abc-- somewhere.

Your email would look something like this:

--abc--    <--actual boundary
This is my email. There are many like it, but this one is mine.
Now for some reason I'm going to put in a line that shouldn't be there
--abc--    <--part of the email
There it was. Did you see it? No, you didn't, because the mail client saw a boundary
line and sliced it out. Because of this extra boundary, now the email has 2 sections,
instead of 1.
--abc--    <--actual boundary

So... How is a mail client to know what's part of the email and what's just "overhead"? That's why you use unique boundaries.

Hashes are simply the easiest method. It's unlikely in the extreme that an email text would happen to contain its own hash value in the exact spot where it could be seen as a boundary marker.

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