Re: [Mailman-Users] Photos from Macs getting removed by list server

[Stephen J. Turnbull]

Peter Shute writes:

 > I wonder how much dangerous javascript in email is these days.

The #infosec and #bitcoin tweeps I follow are all a-twitter about
javascript that mines bitcoins, which is pretty seriously energy- and
cpu-intensive.  (They have opinions at opposite poles though. :-)

It really depends on your list, though.  If very little spam (by that
I mean less than one per quarter) gets through, and you don't have
Javascript tricksters among the posters, I don't see why this would be
a major worry.  Your paranoia level is your choice, though, and it is
less risky if you have a few people with skills who can identify
problematic mail and tell you about it.

Steve

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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Mark Sapiro]

On 01/22/2018 06:58 PM, Peter Shute wrote:
> Lynx? If you mean some kind of customisation, I doubt there's any.

I mean the default conversion from HTML to plain text is done by the command

/usr/bin/lynx -dump %(filename)s

On all the mailman 2.1 installations that I manage, this is changed to

/usr/bin/links -dump %(filename)s

or

/usr/bin/elinks -dump %(filename)s

because I like the output from (e)links better although it's very
similar. It just has less extraneous white space.

Both (e)links and lynx deal with URLs by displaying the text along with
a reference to a footnote containing the actual URL. I don't know how
they deal with an  tag referencing an included image by
Content-ID, but whatever they do may or may not be satisfactory in your
situation. You just have to try it and see.

-- 
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San Francisco Bay Area, Californiabetter use your sense - B. Dylan
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Peter Shute]

Lynx? If you mean some kind of customisation, I doubt there's any.

Peter Shute

> -Original Message-
> From: Mailman-Users [mailto:mailman-users-
> bounces+pshute=nuw.org...@python.org] On Behalf Of Mark Sapiro
> Sent: Tuesday, 23 January 2018 1:21 PM
> To: mailman-users@python.org
> Subject: Re: [Mailman-Users] Photos from Macs getting removed by list
> server
> 
> On 01/22/2018 06:10 PM, Peter Shute wrote:
> >
> > What happens if we just change collapse_alternatives to No?
> 
> 
> You can try that first. It will make a noticeable difference, but the result 
> may
> still not be what you want depending on what 'lynx' or whatever you may
> have changed HTML_TO_PLAIN_TEXT_COMMAND to does with the HTML
> and how the end user MUAs handle it.
> 
> It will result in the images not being removed, but the end rendering of the
> message may or may not be acceptable. You'll have to try it and see.
> 
> --
> Mark Sapiro <m...@msapiro.net>The highway is for gamblers,
> San Francisco Bay Area, Californiabetter use your sense - B. Dylan
> --
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Peter Shute]

I agree about html email, but it was always an uphill battle with Outlook being 
set to html format by default. With iPhones/iPads, there seems to not even be a 
choice. They seem to create plain text unless you add a photo, then they revert 
to html. Our list needs to allow photos, so we just have to try t deal with it.

Peter Shute

> -Original Message-
> From: Mailman-Users [mailto:mailman-users-
> bounces+pshute=nuw.org...@python.org] On Behalf Of Lindsay Haisley
> Sent: Tuesday, 23 January 2018 1:37 PM
> To: mailman-users@python.org
> Subject: Re: [Mailman-Users] Photos from Macs getting removed by list
> server
> 
> On Tue, 2018-01-23 at 02:10 +, Peter Shute wrote:
> > Thanks for all that. I googled collapse_alternatives, and I can see
> > from the colour of some of the results that I've looked this up
> > before.
> >
> > Given that Mac and (particularly) iPhone/iPad users are common, we
> > probably don't have an unusual problem. Maybe I should just ask the
> > list owner to try changing those two settings to see how it goes:
> > collapse_alternatives=No
> > convert_html_to_plaintext=No
> 
> I've been preaching for years to people that using HTML-enhanced email is a
> questionable practice, and on a mailing list it's even worse.
> There is no established standard for this usage, and graphic attachments may
> or may not be handled, or handled as the sender expected. On a mailing list
> it's a pretty sure bet that at least _some_ subscribers won't be able to see
> what the sender intended, so SOP on the lists here is to just strip them off.
> An email with _only_ an HTML MIME part is identified as spam.
> 
> Smart phones have complicated the issue since in my experience smart
> phone MUAs are fairly brain-dead.
> 
> I tell my Mailman mailing list customers that spot color, font effects 
> (bolding,
> italics, etc) and simple layout are probably fine, but the use of images, 
> either
> embedded or attached, is dicey.
> 
> It used to be that HTML-ized emails were up to 10 times the size of plain text
> emails, depending on the generating MUA. This is probably still true, but
> bandwidth and storage capacities around the Internet have risen over the
> years so that this isn't the problem it used to be.
> 
> --
> Lindsay Haisley   | "The first casualty when
> FMP Computer Services | war comes is truth."
> 512-259-1190  |
> http://www.fmp.com| -- Hiram W Johnson
> 
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Lindsay Haisley]

On Tue, 2018-01-23 at 02:10 +, Peter Shute wrote:
> Thanks for all that. I googled collapse_alternatives, and I can see
> from the colour of some of the results that I've looked this up
> before.
> 
> Given that Mac and (particularly) iPhone/iPad users are common, we
> probably don't have an unusual problem. Maybe I should just ask the
> list owner to try changing those two settings to see how it goes:
> collapse_alternatives=No
> convert_html_to_plaintext=No

I've been preaching for years to people that using HTML-enhanced email
is a questionable practice, and on a mailing list it's even worse.
There is no established standard for this usage, and graphic
attachments may or may not be handled, or handled as the sender
expected. On a mailing list it's a pretty sure bet that at least _some_
subscribers won't be able to see what the sender intended, so SOP on
the lists here is to just strip them off. An email with _only_ an HTML
MIME part is identified as spam.

Smart phones have complicated the issue since in my experience smart
phone MUAs are fairly brain-dead.

I tell my Mailman mailing list customers that spot color, font effects
(bolding, italics, etc) and simple layout are probably fine, but the
use of images, either embedded or attached, is dicey.

It used to be that HTML-ized emails were up to 10 times the size of
plain text emails, depending on the generating MUA. This is probably
still true, but bandwidth and storage capacities around the Internet
have risen over the years so that this isn't the problem it used to be.

-- 
Lindsay Haisley   | "The first casualty when
FMP Computer Services | war comes is truth."
512-259-1190  |
http://www.fmp.com| -- Hiram W Johnson

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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Mark Sapiro]

On 01/22/2018 06:10 PM, Peter Shute wrote:
> 
> What happens if we just change collapse_alternatives to No?


You can try that first. It will make a noticeable difference, but the
result may still not be what you want depending on what 'lynx' or
whatever you may have changed HTML_TO_PLAIN_TEXT_COMMAND to does with
the HTML and how the end user MUAs handle it.

It will result in the images not being removed, but the end rendering of
the message may or may not be acceptable. You'll have to try it and see.

-- 
Mark Sapiro The highway is for gamblers,
San Francisco Bay Area, Californiabetter use your sense - B. Dylan
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Peter Shute]

Thanks for all that. I googled collapse_alternatives, and I can see from the 
colour of some of the results that I've looked this up before.

Given that Mac and (particularly) iPhone/iPad users are common, we probably 
don't have an unusual problem. Maybe I should just ask the list owner to try 
changing those two settings to see how it goes:
collapse_alternatives=No
convert_html_to_plaintext=No

I wonder how much dangerous javascript in email is these days.

What happens if we just change collapse_alternatives to No?

> -Original Message-
> From: Mark Sapiro [mailto:m...@msapiro.net]
> Sent: Tuesday, 23 January 2018 12:08 PM
> To: Peter Shute <psh...@nuw.org.au>; mailman-users@python.org
> Subject: Re: [Mailman-Users] Photos from Macs getting removed by list
> server
> 
> On 01/22/2018 01:33 PM, Peter Shute wrote:
> >
> > Perhaps I've used the wrong terminology. I mean that
> convert_html_to_plaintext is set to Yes.
> 
> 
> OK
> 
> 
> > I've attached a screenshot of the content filtering page. Does that
> > tell you everything you need to know? (Assuming it'll be allowed
> > through. If not, what's the easiest way to list all the settings?)
> 
> 
> It didn't go to the list, but I got it in my direct copy. For future 
> reference, the
> settings are:
> 
> filter_content: Yes
> filter_mime_types: empty
> pass_mime_types:
>   multipart
>   text/plain
>   text/html
>   image/jpeg
>   image/png
> filter_filename_extensions:
>   exe
>   bat
>   cmd
>   com
>   pif
>   scr
>   vbs
>   cpl
>   mpg
>   mc4
>   mp3
>   And more not in the screenshot
> pass_filename_extensions: empty
> collapse_alternatives: Yes
> convert_html_to_plaintext: Yes
> filter_action: Discard
> 
> And something like the above is the best way to report them.
> 
> 
> > I still have all the moderation notification emails, with the original 
> > emails
> attached. Can I use those to get the information you need?
> 
> 
> Yes, but see below.
> 
> 
> > But before I start trying to gather together evidence, could we "fix" this
> problem by setting convert_html_to_plaintext to No? If so, are there any
> side effects of that we should know about before we try it?
> 
> 
> That alone probably won't fix it. Consider a message with the following MIME
> structure:
> 
> multipart/alternative
> text/plain
> plain text body
> multipart/related
> text/html
>  HTML body that references images
> image/jpeg
> first image
> image/jpeg
> second image
> 
> pass_mime_types will accept everything, but collapse_alternatives = Yes will
> replace the multipart/alternative part with the first sub-part, i.e. the
> text/plain part leaving only
> 
> text/plain
> plain text body
> 
> as the message to be delivered.
> 
> Even a different message like
> 
> multipart/related
> multipart/alternative
> text/plain
> plain text body
> text/html
>  HTML body that references images
> image/jpeg
> first image
> image/jpeg
> second image
> 
> Will result in the filtered message
> 
> multipart/related
> text/plain
> plain text body
> image/jpeg
> first image
> image/jpeg
> second image
> 
> with the image parts still in the delivered message, but the HTML that
> referenced them gone.
> 
> The only time the HTML is left in the message in any form is if it's not in a
> multipart/alternative sub-part such as
> 
> multipart/related
> text/html
> HTML body that references images
> image/jpeg
> first image
> image/jpeg
> second image
> 
> but even here, the text/html part will be converted to text/plain by
> HTML_TO_PLAIN_TEXT_COMMAND and how the result will render will vary
> depending both on what that command does and the MUA that views the
> result.
> 
> 
> > I'm not the owner of the list, and it wasn't my decision to set it to Yes. 
> > I'm
> under the impression that the owner changed it as a precaution once after
> the list was somehow being used to send out spam. It's my impression that in
> the years before I had admin access, there have been periods when html
> was allowed, but I have no idea of the reasons for the earlier changes.
> 
> 
> You definitely want to set collapse_alternatives to No. Depending on how
> that works for you, you may also need to set convert_html_to_plaintext to
> No to get the result you want.
> 
> The risk in setting convert_html_to_plaintext to No is mes

Re: [Mailman-Users] Photos from Macs getting removed by list server

[Mark Sapiro]

On 01/22/2018 01:33 PM, Peter Shute wrote:
> 
> Perhaps I've used the wrong terminology. I mean that 
> convert_html_to_plaintext is set to Yes.


OK


> I've attached a screenshot of the content filtering page. Does that tell you 
> everything you need to know? (Assuming it'll be allowed through. If not, 
> what's the easiest way to list all the settings?)


It didn't go to the list, but I got it in my direct copy. For future
reference, the settings are:

filter_content: Yes
filter_mime_types: empty
pass_mime_types:
  multipart
  text/plain
  text/html
  image/jpeg
  image/png
filter_filename_extensions:
  exe
  bat
  cmd
  com
  pif
  scr
  vbs
  cpl
  mpg
  mc4
  mp3
  And more not in the screenshot
pass_filename_extensions: empty
collapse_alternatives: Yes
convert_html_to_plaintext: Yes
filter_action: Discard

And something like the above is the best way to report them.


> I still have all the moderation notification emails, with the original emails 
> attached. Can I use those to get the information you need?


Yes, but see below.


> But before I start trying to gather together evidence, could we "fix" this 
> problem by setting convert_html_to_plaintext to No? If so, are there any side 
> effects of that we should know about before we try it?


That alone probably won't fix it. Consider a message with the following
MIME structure:

multipart/alternative
text/plain
plain text body
multipart/related
text/html
 HTML body that references images
image/jpeg
first image
image/jpeg
second image

pass_mime_types will accept everything, but collapse_alternatives = Yes
will replace the multipart/alternative part with the first sub-part,
i.e. the text/plain part leaving only

text/plain
plain text body

as the message to be delivered.

Even a different message like

multipart/related
multipart/alternative
text/plain
plain text body
text/html
 HTML body that references images
image/jpeg
first image
image/jpeg
second image

Will result in the filtered message

multipart/related
text/plain
plain text body
image/jpeg
first image
image/jpeg
second image

with the image parts still in the delivered message, but the HTML that
referenced them gone.

The only time the HTML is left in the message in any form is if it's not
in a multipart/alternative sub-part such as

multipart/related
text/html
HTML body that references images
image/jpeg
first image
image/jpeg
second image

but even here, the text/html part will be converted to text/plain by
HTML_TO_PLAIN_TEXT_COMMAND and how the result will render will vary
depending both on what that command does and the MUA that views the result.


> I'm not the owner of the list, and it wasn't my decision to set it to Yes. 
> I'm under the impression that the owner changed it as a precaution once after 
> the list was somehow being used to send out spam. It's my impression that in 
> the years before I had admin access, there have been periods when html was 
> allowed, but I have no idea of the reasons for the earlier changes.


You definitely want to set collapse_alternatives to No. Depending on how
that works for you, you may also need to set convert_html_to_plaintext
to No to get the result you want.

The risk in setting convert_html_to_plaintext to No is messages with
evil javascript will go to the list.

-- 
Mark Sapiro The highway is for gamblers,
San Francisco Bay Area, Californiabetter use your sense - B. Dylan
--
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Peter Shute]

Mark Sapiro wrote:

> > If the list is plain-text only, I'd be more curious how images were
> > making their way through, not the reverse.
> 
> Exactly!

Perhaps I've used the wrong terminology. I mean that convert_html_to_plaintext 
is set to Yes.

> In order to say more, we'd need to see all the content filtering settings for
> the list and the emails at issue. Ideally, we'd like a raw email as sent to 
> the
> list, but even the resultant email from the list might be helpful.

I've attached a screenshot of the content filtering page. Does that tell you 
everything you need to know? (Assuming it'll be allowed through. If not, what's 
the easiest way to list all the settings?)

> I.e., for the ideal case, have the user mail to the list with a Bcc: to you. 
> Then,
> show us the content filtering settings and both raw emails, the list mail and
> the direct Bcc:.

I still have all the moderation notification emails, with the original emails 
attached. Can I use those to get the information you need?

But before I start trying to gather together evidence, could we "fix" this 
problem by setting convert_html_to_plaintext to No? If so, are there any side 
effects of that we should know about before we try it?

I'm not the owner of the list, and it wasn't my decision to set it to Yes. I'm 
under the impression that the owner changed it as a precaution once after the 
list was somehow being used to send out spam. It's my impression that in the 
years before I had admin access, there have been periods when html was allowed, 
but I have no idea of the reasons for the earlier changes.

Peter Shute
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Mark Sapiro]

On 01/21/2018 11:52 PM, Stephen J. Turnbull wrote:
> 
> If you have access to the host or perhaps through the web interface to
> the archives, you can get the "mbox" files.  This is typically in
> /var/lib/mailman/archives/private/LIST.mbox/LIST.mbox, where LIST is
> the mailbox name (the posting address) for the list.  These contain
> full messages, including attachments.


After content filtering.


> You can read these with a text editor or pager, and should be able to
> find the original messages that cause problems.


The original message as received by Mailman before content filtering
isn't saved anywhere.

-- 
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San Francisco Bay Area, Californiabetter use your sense - B. Dylan
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[Mailman-Users] Photos from Macs getting removed by list server

[Stephen J. Turnbull]

Peter Shute writes:

 > Evidence for these symptoms is partly anecdotal, so might not be
 > exactly right. It’s hard to get information from users about
 > exactly which device and which program they used to create the
 > emails. Has anyone else seen the same things? Is there any easy fix
 > for them?

If you have access to the host or perhaps through the web interface to
the archives, you can get the "mbox" files.  This is typically in
/var/lib/mailman/archives/private/LIST.mbox/LIST.mbox, where LIST is
the mailbox name (the posting address) for the list.  These contain
full messages, including attachments.

You can read these with a text editor or pager, and should be able to
find the original messages that cause problems.  There will often
be a User-Agent: or X-Mailer: header field which describes the mail
program that composed the message.

There are a number of unusual aspects to mail with Apple devices, I
believe primarily when using Apple's Mail program, and I know that
it's finicky about reading mail.  Specifically, as other replies
mentioned, they like to embed non-text media in HTML rather than
attach them to the mail.  Other than that I can't say much.  It would
help to see examples of failing messages, both in the LIST.mbox format
and as saved in the YEAR-MONTH.txt files (which you can find below
"public" next to the "private" folder, or in the "private" folder for
private lists).

Feel free to either redact identifying information or send any example
messages to me or Mark or both at our personal addresses.  What's
important to solving the problems are the message and part headers,
and the HTML structure.  It's also helpful if the attachments are
undisturbed.

If any of the above makes no sense, feel free to ask for more explicit
instructions.  This stuff is tedious, and Mark and I not only wasted
our youth but much of our adult life learning it.  We wouldn't impose
that on you! :-)

Steve

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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Mark Sapiro]

On 01/21/2018 09:30 AM, Carl Zwanzig wrote:
> On 1/21/2018 12:13 AM, Peter Shute wrote:
>> We’re finding that messages sent to our list by Mac users are having
>> jpg attachments removed. I assume this is something to do with the
>> list being plain text only...
> 
> If the list is plain-text only, I'd be more curious how images were
> making their way through, not the reverse.


Exactly!

In order to say more, we'd need to see all the content filtering
settings for the list and the emails at issue. Ideally, we'd like a raw
email as sent to the list, but even the resultant email from the list
might be helpful.

I.e., for the ideal case, have the user mail to the list with a Bcc: to
you. Then, show us the content filtering settings and both raw emails,
the list mail and the direct Bcc:.

-- 
Mark Sapiro The highway is for gamblers,
San Francisco Bay Area, Californiabetter use your sense - B. Dylan
--
Mailman-Users mailing list Mailman-Users@python.org
https://mail.python.org/mailman/listinfo/mailman-users
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Richard Damon]

On 1/21/18 12:30 PM, Carl Zwanzig wrote:

On 1/21/2018 12:13 AM, Peter Shute wrote:
We’re finding that messages sent to our list by Mac users are having 
jpg attachments removed. I assume this is something to do with the 
list being plain text only...


If the list is plain-text only, I'd be more curious how images were 
making their way through, not the reverse.


z! 
For what is normally called a 'plain text only list', yes, I would be 
very surprised to see any pictures. I think it may be possible by 
enabling the HTML -> Text conversion, but NOT filtering out non-text 
sections, you might be able to create a semi-text only list, and in such 
a case, there may be ways to embed an image inline that it gets lost, as 
well as including the image as its own section so it gets through.


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Richard Damon

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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Carl Zwanzig]

On 1/21/2018 12:13 AM, Peter Shute wrote:

We’re finding that messages sent to our list by Mac users are having jpg 
attachments removed. I assume this is something to do with the list being plain 
text only...


If the list is plain-text only, I'd be more curious how images were making 
their way through, not the reverse.


z!
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Re: [Mailman-Users] Photos from Macs getting removed by list server

[Christian F Buser via Mailman-Users]

Hello Peter Shute. On Sun, 21 Jan 2018 08:13:13 +, you wrote:

> We’re finding that messages sent to our list by Mac users are having 
> jpg attachments removed. I assume this is something to do with the 
> list being plain text only, and the email format created by the mail 
> program Macs use.

No, it has nothing to do with "the email format created by the mail program 
Macs use", because these mail programs have to follow the same rules as all 
mail programs do. Otherwise they just would be useless.

I would rather guess that these images were embedded in the mail message’s HTML 
text and not real attachments. And when the HTML is deleted by Mailman, the 
images are of course also no longer showing. 

> We’re also finding that if ipad/iphone users send emails with photos, 
> the list lets the photos through, but iPad/iphone users can’t see 
> them, causing them to assume they’ve been stripped off.

Not sure, but I think this is all a problem between the chair and the keyboard 
of the sender or the recipient... 

Christian 

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[Mailman-Users] Photos from Macs getting removed by list server

[Peter Shute]

We’re finding that messages sent to our list by Mac users are having jpg 
attachments removed. I assume this is something to do with the list being plain 
text only, and the email format created by the mail program Macs use.

We’re also finding that if ipad/iphone users send emails with photos, the list 
lets the photos through, but iPad/iphone users can’t see them, causing them to 
assume they’ve been stripped off.

Evidence for these symptoms is partly anecdotal, so might not be exactly right. 
It’s hard to get information from users about exactly which device and which 
program they used to create the emails. Has anyone else seen the same things? 
Is there any easy fix for them?

Peter Shute

Sent from my iPad
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