On Sat, Apr 03, 2010 at 11:39:01AM -0700, Michael Elkins wrote:
While reading this bug report http://dev.mutt.org/trac/ticket/3400 about
lack of documentation for the mailto: support, and reading the current
security warning about use of mailto:, I came to the conclusion that the
current method is insecure.
This patch adds two new commands:
mailto_allow header-field [...]
unmailto_allow [ * | header-field ... ]
which control a whitelist of allowed header fields that Mutt will
process from a mailto: URL. By default only "subject" and "body" are on
the list, as specified by RFC2368.
updated to work with the patch in bug #3441. me
# HG changeset patch
# User Michael Elkins <me@xxxxxxxx>
# Date 1281370900 25200
# Branch HEAD
# Node ID e71bc0d5914fdb63e4bab4f7b227c2b31b7ec59c
# Parent 5dca5158b4962d63b3b3ab11248bb737af49a84f
add whitelist/blacklist for header fields in mailto: urls
diff --git a/doc/manual.xml.head b/doc/manual.xml.head
--- a/doc/manual.xml.head
+++ b/doc/manual.xml.head
@@ -4620,6 +4620,37 @@
</sect1>
+<sect1 id="mailto-allow">
+<title>Control allowed header fields in a mailto: URL</title>
+
+<para>Usage:</para>
+
+<cmdsynopsis>
+<command>mailto_allow</command>
+<group choice="req">
+<arg choice="plain">
+<replaceable class="parameter">*</replaceable>
+</arg>
+<arg choice="plain" rep="repeat">
+<replaceable class="parameter">header-field</replaceable>
+</arg>
+</group>
+</cmdsynopsis>
+
+<para>
+As a security measure, Mutt will only add user-approved header fields from a
+<literal>mailto:</literal> URL. This is necessary since Mutt will handle
+certain header fields, such as <literal>Attach:</literal>, in a special way.
+The <literal>mailto_allow</literal> and <literal>unmailto_allow</literal>
+commands allow the user to modify the list of approved headers.
+</para>
+<para>
+Mutt initializes the default list to contain only the
<literal>Subject</literal>
+and <literal>body</literal> header fields, which are the only requirement
specified
+by the <literal>mailto:</literal> specification in RFC2368.
+</para>
+</sect1>
+
</chapter>
<chapter id="advancedusage">
diff --git a/doc/muttrc.man.head b/doc/muttrc.man.head
--- a/doc/muttrc.man.head
+++ b/doc/muttrc.man.head
@@ -399,6 +399,16 @@
This command will remove all hooks of a given type, or all hooks
when \(lq\fB*\fP\(rq is used as an argument. \fIhook-type\fP
can be any of the \fB-hook\fP commands documented above.
+.PP
+.nf
+\fBmailto_allow\fP \fIheader-field\fP [ ... ]
+\fBunmailto_allow\fP [ \fB*\fP | \fIheader-field\fP ... ]
+.fi
+.IP
+These commands allow the user to modify the list of allowed header
+fields in a \fImailto:\fP URL that Mutt will include in the
+the generated message. By default the list contains only
+\fBsubject\fP and \fBbody\fP, as specified by RFC2368.
.SH PATTERNS
.PP
In various places with mutt, including some of the above mentioned
diff --git a/globals.h b/globals.h
--- a/globals.h
+++ b/globals.h
@@ -159,6 +159,7 @@
WHERE LIST *InlineExclude INITVAL(0);
WHERE LIST *HeaderOrderList INITVAL(0);
WHERE LIST *Ignore INITVAL(0);
+WHERE LIST *MailtoAllow INITVAL(0);
WHERE LIST *MimeLookupList INITVAL(0);
WHERE LIST *UnIgnore INITVAL(0);
diff --git a/init.c b/init.c
--- a/init.c
+++ b/init.c
@@ -3052,6 +3052,15 @@
mutt_init_history ();
+ /* RFC2368, "4. Unsafe headers"
+ * The creator of a mailto URL cannot expect the resolver of a URL to
+ * understand more than the "subject" and "body" headers. Clients that
+ * resolve mailto URLs into mail messages should be able to correctly
+ * create RFC 822-compliant mail messages using the "subject" and "body"
+ * headers.
+ */
+ add_to_list(&MailtoAllow, "body");
+ add_to_list(&MailtoAllow, "subject");
diff --git a/init.h b/init.h
--- a/init.h
+++ b/init.h
@@ -3486,6 +3486,8 @@
{ "macro", mutt_parse_macro, 0 },
{ "mailboxes", mutt_parse_mailboxes, M_MAILBOXES },
{ "unmailboxes", mutt_parse_mailboxes, M_UNMAILBOXES },
+ { "mailto_allow", parse_list, UL &MailtoAllow },
+ { "unmailto_allow", parse_unlist, UL &MailtoAllow },
{ "message-hook", mutt_parse_hook, M_MESSAGEHOOK },
{ "mbox-hook", mutt_parse_hook, M_MBOXHOOK },
{ "mime_lookup", parse_list, UL &MimeLookupList },
diff --git a/url.c b/url.c
--- a/url.c
+++ b/url.c
@@ -283,20 +283,34 @@
if (url_pct_decode (value) < 0)
goto out;
- if (!ascii_strcasecmp (tag, "body"))
+ /* Determine if this header field is on the allowed list. Since Mutt
+ * interprets some header fields specially (such as
+ * "Attach: ~/.gnupg/secring.gpg"), care must be taken to ensure that
+ * only safe fields are allowed.
+ *
+ * RFC2368, "4. Unsafe headers"
+ * The user agent interpreting a mailto URL SHOULD choose not to create
+ * a message if any of the headers are considered dangerous; it may also
+ * choose to create a message with only a subset of the headers given in
+ * the URL.
+ */
+ if (mutt_matches_ignore(tag, MailtoAllow))
{
- if (body)
- mutt_str_replace (body, value);
- }
- else
- {
- char *scratch = mutt_sprintf ("%s: %s", tag, value);
- size_t taglen = mutt_strlen (tag);
- scratch[taglen] = 0; /* overwrite the colon as mutt_parse_rfc822_line
expects */
- value = &scratch[taglen + 1];
- SKIPWS (value);
- mutt_parse_rfc822_line (e, NULL, scratch, value, 1, 0, 0, &last);
- FREE (&scratch);
+ if (!ascii_strcasecmp (tag, "body"))
+ {
+ if (body)
+ mutt_str_replace (body, value);
+ }
+ else
+ {
+ char *scratch = mutt_sprintf ("%s: %s", tag, value);
+ size_t taglen = mutt_strlen (tag);
+ scratch[taglen] = 0; /* overwrite the colon as mutt_parse_rfc822_line
expects */
+ value = &scratch[taglen + 1];
+ SKIPWS (value);
+ mutt_parse_rfc822_line (e, NULL, scratch, value, 1, 0, 0, &last);
+ FREE (&scratch);
+ }
}
}
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