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Don't split Quoted Printable characters during folding procedure #22

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merged 1 commit into from
Mar 21, 2018
Merged

Don't split Quoted Printable characters during folding procedure #22

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22 changes: 21 additions & 1 deletion header.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,17 @@ package message
import (
"mime"
"net/textproto"
"regexp"
"strings"

"github.com/emersion/go-message/charset"
)

const maxHeaderLen = 76

// Regexp that detects Quoted Printable (QP) characters
var qpReg = regexp.MustCompile("(=[0-9A-Z]{2,2})+")

func parseHeaderWithParams(s string) (f string, params map[string]string, err error) {
f, params, err = mime.ParseMediaType(s)
if err != nil {
Expand Down Expand Up @@ -59,8 +63,24 @@ func formatHeaderField(k, v string) string {
folding = "\r\n"
}
} else {
// Find the last QP character before limit
foldAtQP := qpReg.FindAllStringIndex(v[:foldBefore], -1)
// Find the closest whitespace before i
foldAt = strings.LastIndexAny(v[:foldBefore], " \t\n")
foldAtEOL := strings.LastIndexAny(v[:foldBefore], " \t\n")

// Fold at the latest whitespace by default
foldAt = foldAtEOL

// if there are QP characters in the string
if len(foldAtQP) > 0 {
// Get the start index of the last QP character
foldAtQPLastIndex := foldAtQP[len(foldAtQP)-1][0]
if foldAtQPLastIndex > foldAt {
// Fold at the latest QP character if there are no whitespaces after it and before line hard limit
foldAt = foldAtQPLastIndex
}
}

if foldAt == 0 {
// The whitespace we found was the previous folding WSP
foldAt = foldBefore - 1
Expand Down
15 changes: 15 additions & 0 deletions header_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,21 @@ var formatHeaderFieldTests = []struct {
v: "This is yet \t another subject \t with many whitespace characters",
formatted: "Subject: This is yet \t another subject \t \r\n with many whitespace characters\r\n",
},
{
k: "Subject",
v: "=?utf-8?q?=E2=80=9CDeveloper_reads_customer_requested_change.=E2=80=9D=0A?= =?utf-8?q?=0ACaravaggio=0A=0AOil_on...?=",
formatted: "Subject: =?utf-8?q?=E2=80=9CDeveloper_reads_customer_requested_change.\r\n =E2=80=9D=0A?= =?utf-8?q?=0ACaravaggio=0A=0AOil_on...?=\r\n",
},
{
k: "Subject",
v: "=?utf-8?q?=E2=80=9CShort subject=E2=80=9D=0A?= =?utf-8?q?=0AAuthor=0A=0AOil_on...?=",
formatted: "Subject: =?utf-8?q?=E2=80=9CShort subject=E2=80=9D=0A?= =?utf-8?q?\r\n =0AAuthor=0A=0AOil_on...?=\r\n",
},
{
k: "Subject",
v: "=?utf-8?q?=E2=80=9CVery long subject very long subject very long subject very long subject=E2=80=9D=0A?= =?utf-8?q?=0ALong second part of subject long second part of subject long second part of subject long subject=0A=0AOil_on...?=",
formatted: "Subject: =?utf-8?q?=E2=80=9CVery long subject very long subject very long\r\n subject very long subject=E2=80=9D=0A?= =?utf-8?q?=0ALong second part of\r\n subject long second part of subject long second part of subject long\r\n subject=0A=0AOil_on...?=\r\n",
},
{
k: "DKIM-Signature",
v: "v=1;\r\n h=From:To:Reply-To:Subject:Message-ID:References:In-Reply-To:MIME-Version;\r\n d=example.org\r\n",
Expand Down