# [PATCH] mailinfo: don't decode invalid =XY quoted-printable sequences 3 messages from 2017-09-23 to 2017-09-25. Participants: René Scharfe, Jeff King. Thread: https://gitlist.dev/t/46817 ## René Scharfe, 2017-09-23 18:04 Subject: [PATCH] mailinfo: don't decode invalid =XY quoted-printable sequences Message-ID: URL: https://gitlist.dev/e/d48b3d67-5f03-19f3-5a32-ec7e8397c98d%40web.de ``` Decode =XY in quoted-printable segments only if X and Y are hexadecimal digits, otherwise just copy them. That's at least better than interpreting negative results from hexval() as a character. Signed-off-by: Rene Scharfe --- mailinfo.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/mailinfo.c b/mailinfo.c index f2387a3267..3d8ac07399 100644 --- a/mailinfo.c +++ b/mailinfo.c @@ -367,11 +367,16 @@ static struct strbuf *decode_q_segment(const struct strbuf *q_seg, int rfc2047) while ((c = *in++) != 0) { if (c == '=') { - int d = *in++; + int ch, d = *in; if (d == '\n' || !d) break; /* drop trailing newline */ - strbuf_addch(out, (hexval(d) << 4) | hexval(*in++)); - continue; + ch = hex2chr(in); + if (ch >= 0) { + strbuf_addch(out, ch); + in += 2; + continue; + } + /* garbage -- fall through */ } if (rfc2047 && c == '_') /* rfc2047 4.2 (2) */ c = 0x20; -- 2.14.1 ``` ## René Scharfe, 2017-09-23 18:36 Subject: Re: [PATCH] mailinfo: don't decode invalid =XY quoted-printable sequences Message-ID: URL: https://gitlist.dev/e/f06d0701-281c-07eb-d053-78b8fcdd00c4%40web.de In-Reply-To: ``` Am 23.09.2017 um 20:04 schrieb René Scharfe: > Decode =XY in quoted-printable segments only if X and Y are hexadecimal > digits, otherwise just copy them. That's at least better than > interpreting negative results from hexval() as a character. Forgot to add: Reported-by: Jeff King René ``` ## Jeff King, 2017-09-25 12:28 Subject: Re: [PATCH] mailinfo: don't decode invalid =XY quoted-printable sequences Message-ID: <20170925122844.lwzwtp2u4dhgijrd@sigill.intra.peff.net> URL: https://gitlist.dev/e/20170925122844.lwzwtp2u4dhgijrd%40sigill.intra.peff.net In-Reply-To: ``` On Sat, Sep 23, 2017 at 08:04:40PM +0200, René Scharfe wrote: > Decode =XY in quoted-printable segments only if X and Y are hexadecimal > digits, otherwise just copy them. That's at least better than > interpreting negative results from hexval() as a character. Thanks, this looks good to me overall. I wondered if we should die() here, but walking over cruft may be more friendly. The base64 case does the same, though it actually ignores the bytes rather than copying them. Since this is never _supposed_ to happen, it's hard to say what behavior would be preferable without seeing a real-world broken case. -Peff ```