ircd.chat/irc-go
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Make truncation UTF8-safe

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We should never truncate in the middle of a UTF8 codepoint.
Enabling this unconditionally, since truncation is most likely
implementation-defined.
This commit is contained in:
Shivaram Lingamneni 2021-03-02 14:55:22 -05:00
parent d39993c074
commit 0c71162327
1 changed files with 21 additions and 6 deletions
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27
ircmsg/message.go
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@ -9,6 +9,7 @@ import (
"bytes"
"errors"
"strings"
"unicode/utf8"
)
const (
@ -161,7 +162,7 @@ func ParseLineStrict(line string, fromClient bool, truncateLen int) (ircmsg IRCM
// slice off any amount of ' ' from the front of the string
func trimInitialSpaces(str string) string {
var i int
for i = 0; i < len(str) && str[i] == ' '; i += 1 {
for i = 0; i < len(str) && str[i] == ' '; i++ {
}
return str[i:]
}
@ -408,11 +409,25 @@ func (ircmsg *IRCMessage) line(tagLimit, clientOnlyTagDataLimit, serverAddedTagD
buf.WriteString(param)
}
// truncate if desired
// -2 for \r\n
restLen := buf.Len() - lenTags
if 0 < truncateLen && (truncateLen-2) < restLen {
buf.Truncate(lenTags + (truncateLen - 2))
// truncate if desired; leave 2 bytes over for \r\n:
if truncateLen != 0 && (truncateLen-2) < (buf.Len()-lenTags) {
newBufLen := lenTags + (truncateLen - 2)
buf.Truncate(newBufLen)
// XXX: we may have truncated in the middle of a UTF8-encoded codepoint;
// if so, remove additional bytes, stopping when the sequence either
// ends in a valid codepoint, or we have removed 3 bytes (the maximum
// length of the remnant of a once-valid, truncated codepoint; we don't
// want to truncate the entire message if it wasn't UTF8 in the first
// place).
for i := 0; i < (utf8.UTFMax - 1); i++ {
r, n := utf8.DecodeLastRune(buf.Bytes())
if r == utf8.RuneError && n <= 1 {
newBufLen--
buf.Truncate(newBufLen)
} else {
break
}
}
}
buf.WriteString("\r\n")