mailinfo: warn if CRLF found in decoded base64/QP email

When SMTP servers receive 8-bit email messages, possibly with only
LF as line ending, some of them decide to change said LF to CRLF.

Some mailing list softwares, when receive 8-bit email messages,
decide to encode those messages in base64 or quoted-printable.

If an email is transfered through above mail servers, then distributed
by such mailing list softwares, the recipients will receive an email
contains a patch mungled with CRLF encoded inside another encoding.

Thus, such CR (in CRLF) couldn't be dropped by "mailsplit".
Hence, the mailed patch couldn't be applied cleanly.
Such accidents have been observed in the wild [1].

Instead of silently rejecting those messages, let's give our users
some warnings if such CR (as part of CRLF) is found.

[1]: https://nmbug.notmuchmail.org/nmweb/show/m2lf9ejegj.fsf%40guru.guru-group.fi

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/mailinfo.c b/mailinfo.c
index 5681d9130db6f54971cf2b966d1743b87a130b86..c8caee4f55b1bab1e1d8fac63c0e448be8db8d0a 100644 (file)
--- a/mailinfo.c
+++ b/mailinfo.c
@@ -994,6 +994,11 @@ static void handle_filter_flowed(struct mailinfo *mi, struct strbuf *line,
        const char *rest;
 
        if (!mi->format_flowed) {
+               if (len >= 2 &&
+                   line->buf[len - 2] == '\r' &&
+                   line->buf[len - 1] == '\n') {
+                       mi->have_quoted_cr = 1;
+               }
                handle_filter(mi, line);
                return;
        }
@@ -1033,6 +1038,12 @@ static void handle_filter_flowed(struct mailinfo *mi, struct strbuf *line,
        handle_filter(mi, line);
 }
 
+static void summarize_quoted_cr(struct mailinfo *mi)
+{
+       if (mi->have_quoted_cr)
+               warning(_("quoted CRLF detected"));
+}
+
 static void handle_body(struct mailinfo *mi, struct strbuf *line)
 {
        struct strbuf prev = STRBUF_INIT;
@@ -1051,6 +1062,8 @@ static void handle_body(struct mailinfo *mi, struct strbuf *line)
                                handle_filter(mi, &prev);
                                strbuf_reset(&prev);
                        }
+                       summarize_quoted_cr(mi);
+                       mi->have_quoted_cr = 0;
                        if (!handle_boundary(mi, line))
                                goto handle_body_out;
                }
@@ -1100,6 +1113,7 @@ static void handle_body(struct mailinfo *mi, struct strbuf *line)
 
        if (prev.len)
                handle_filter(mi, &prev);
+       summarize_quoted_cr(mi);
 
        flush_inbody_header_accum(mi);
 

diff --git a/mailinfo.h b/mailinfo.h
index 79b1d6774ec9ea8a2ef7a6303abb9fc1c917c36f..b394ef9bcee0467826b9cb0bd4e7b50327969e5e 100644 (file)
--- a/mailinfo.h
+++ b/mailinfo.h
@@ -24,6 +24,7 @@ struct mailinfo {
        struct strbuf charset;
        unsigned int format_flowed:1;
        unsigned int delsp:1;
+       unsigned int have_quoted_cr:1;
        char *message_id;
        enum  {
                TE_DONTCARE, TE_QP, TE_BASE64

diff --git a/t/t5100-mailinfo.sh b/t/t5100-mailinfo.sh
index 147e616533cfd77baa318d37fd85ebd092c141e6..ac6fbfe596c1805fe2d2f70da37583b831c2e24c 100755 (executable)
--- a/t/t5100-mailinfo.sh
+++ b/t/t5100-mailinfo.sh
@@ -228,4 +228,34 @@ test_expect_success 'mailinfo handles unusual header whitespace' '
        test_cmp expect actual
 '
 
+check_quoted_cr_mail () {
+       mail="$1" && shift &&
+       git mailinfo -u "$@" "$mail.msg" "$mail.patch" \
+               <"$mail" >"$mail.info" 2>"$mail.err" &&
+       test_cmp "$mail-expected.msg" "$mail.msg" &&
+       test_cmp "$mail-expected.patch" "$mail.patch" &&
+       test_cmp "$DATA/quoted-cr-info" "$mail.info"
+}
+
+test_expect_success 'split base64 email with quoted-cr' '
+       mkdir quoted-cr &&
+       git mailsplit -oquoted-cr "$DATA/quoted-cr.mbox" >quoted-cr/last &&
+       test $(cat quoted-cr/last) = 2
+'
+
+test_expect_success 'mailinfo warn CR in base64 encoded email' '
+       sed -e "s/%%$//" -e "s/%%/$(printf \\015)/g" "$DATA/quoted-cr-msg" \
+               >quoted-cr/0001-expected.msg &&
+       sed "s/%%/$(printf \\015)/g" "$DATA/quoted-cr-msg" \
+               >quoted-cr/0002-expected.msg &&
+       sed -e "s/%%$//" -e "s/%%/$(printf \\015)/g" "$DATA/quoted-cr-patch" \
+               >quoted-cr/0001-expected.patch &&
+       sed "s/%%/$(printf \\015)/g" "$DATA/quoted-cr-patch" \
+               >quoted-cr/0002-expected.patch &&
+       check_quoted_cr_mail quoted-cr/0001 &&
+       test_must_be_empty quoted-cr/0001.err &&
+       check_quoted_cr_mail quoted-cr/0002 &&
+       grep "quoted CRLF detected" quoted-cr/0002.err
+'
+
 test_done

diff --git a/t/t5100/quoted-cr-info b/t/t5100/quoted-cr-info
new file mode 100644 (file)
index 0000000..dab2228
--- /dev/null
+++ b/t/t5100/quoted-cr-info
@@ -0,0 +1,5 @@
+Author: A U Thor
+Email: mail@example.com
+Subject: sample
+Date: Mon, 3 Aug 2020 22:40:55 +0700
+

diff --git a/t/t5100/quoted-cr-msg b/t/t5100/quoted-cr-msg
new file mode 100644 (file)
index 0000000..89b05a0
--- /dev/null
+++ b/t/t5100/quoted-cr-msg
@@ -0,0 +1,2 @@
+On different distro, %%pytest is suffixed with different patterns.%%
+%%

diff --git a/t/t5100/quoted-cr-patch b/t/t5100/quoted-cr-patch
new file mode 100644 (file)
index 0000000..65b13ee
--- /dev/null
+++ b/t/t5100/quoted-cr-patch
@@ -0,0 +1,22 @@
+---%%
+ configure | 2 +-%%
+ 1 file changed, 1 insertion(+), 1 deletion(-)%%
+%%
+diff --git a/configure b/configure%%
+index db3538b3..f7c1c095 100755%%
+--- a/configure%%
++++ b/configure%%
+@@ -814,7 +814,7 @@ if [ $have_python3 -eq 1 ]; then%%
+     printf "%%Checking for python3 pytest (>= 3.0)... "%%
+     conf=$(mktemp)%%
+     printf "[pytest]\nminversion=3.0\n" > $conf%%
+-    if pytest-3 -c $conf --version >/dev/null 2>&1; then%%
++    if "$python" -m pytest -c $conf --version >/dev/null 2>&1; then%%
+         printf "Yes.\n"%%
+         have_python3_pytest=1%%
+     else%%
+-- %%
+2.28.0%%
+_______________________________________________
+example mailing list -- list@example.org
+To unsubscribe send an email to list-leave@example.org

diff --git a/t/t5100/quoted-cr.mbox b/t/t5100/quoted-cr.mbox
new file mode 100644 (file)
index 0000000..909021b
--- /dev/null
+++ b/t/t5100/quoted-cr.mbox
@@ -0,0 +1,47 @@
+From nobody Mon Sep 17 00:00:00 2001
+From: A U Thor <mail@example.com>
+To: list@example.org
+Subject: [PATCH v2] sample
+Date: Mon,  3 Aug 2020 22:40:55 +0700
+Message-Id: <msg-id@example.com>
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: base64
+
+T24gZGlmZmVyZW50IGRpc3RybywgDXB5dGVzdCBpcyBzdWZmaXhlZCB3aXRoIGRpZmZlcmVudCBw
+YXR0ZXJucy4KCi0tLQogY29uZmlndXJlIHwgMiArLQogMSBmaWxlIGNoYW5nZWQsIDEgaW5zZXJ0
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+c3QtbGVhdmVAZXhhbXBsZS5vcmcK
+
+From nobody Mon Sep 17 00:00:00 2001
+From: A U Thor <mail@example.com>
+To: list@example.org
+Subject: [PATCH v2] sample
+Date: Mon,  3 Aug 2020 22:40:55 +0700
+Message-Id: <msg-id2@example.com>
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: base64
+
+T24gZGlmZmVyZW50IGRpc3RybywgDXB5dGVzdCBpcyBzdWZmaXhlZCB3aXRoIGRpZmZlcmVudCBw
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