ref: 00a00d930aaa0f4915f4ab052dcc55bf6a519eb1
parent: d1ee3f91d97971e4008bb79d6f348ee1d3cd7605
author: Michael Forney <mforney@mforney.org>
date: Mon Feb 8 15:59:01 EST 2021
[9front] upas/vf: exclude mime boundary from temporary attachment files validateattachment has no business with the mime boundary; it is not part of the attachment itself. Also, it causes the boundary to be dropped in the message output from upas/vf, effectively dropping the following attachment (though the content is still present after the last boundary of the wrapped first attachment part). Consider the following sequence of events: 1. upas/vf is run on a message containing two attachments. 2. The first attachment does not have a known extension, so is saved to a temporary file *including* the following mime boundary. 3. This file is opened as p->tmpbuf, which is used for subsequent reads until switching back to stdin. 4. The attachment fails validateattachment, so upas/vf wraps it in a multipart with a warning message. 5. problemchild() calls passbody(p, 0), which copies from p->tmpbuf until it hits the outer boundary line, which it excludes, seeks back one line, then returns the outer multipart. 6. problemchild() then writes its own boundary, and then copies one line from *stdin* to stdout, expecting the outer boundary. However, this boundary was already read from stdin in 2, so it ends up reading the first line of the subsequent part instead. To fix this, pass 0 to passbody() in save() to exclude it from the attachment file and make it available in stdin when expected.
--- a/sys/src/cmd/upas/vf/vf.c
+++ b/sys/src/cmd/upas/vf/vf.c
@@ -387,7 +387,7 @@
Bprint(&out, "From virusfilter %τ\n", thedate(&tm));
writeheader(p, 0);
bodyoff = Boffset(&out);
- passbody(p, 1);
+ passbody(p, 0);
Bprint(&out, "\n");
Bterm(&out);
close(fd);
--
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