Limit unclosed placeholder tolerance (fix #4170)

Matthew Holt committed Sep 15, 2022 at 13:36 UTC 2dc747cf2d7dd4e7337c1d7665042b896f3b4445

1 file changed +12 -1

replacer.go

+12 -1

@@ -144,9 +144,11 @@ func (r *Replacer) replace(input, empty string,

144 // iterate the input to find each placeholder

145 var lastWriteCursor int

146

147 + // fail fast if too many placeholders are unclosed

148 + var unclosedCount int

149 +

150 scan:

151 for i := 0; i < len(input); i++ {

149 -

152 // check for escaped braces

153 if i > 0 && input[i-1] == phEscape && (input[i] == phClose || input[i] == phOpen) {

154 sb.WriteString(input[lastWriteCursor : i-1])

@@ -158,9 +160,17 @@ scan:

160 continue

161 }

162

163 + // our iterator is now on an unescaped open brace (start of placeholder)

164 +

165 + // too many unclosed placeholders in absolutely ridiculous input can be extremely slow (issue #4170)

166 + if unclosedCount > 100 {

167 + return "", fmt.Errorf("too many unclosed placeholders")

168 + }

169 +

170 // find the end of the placeholder

171 end := strings.Index(input[i:], string(phClose)) + i

172 if end < i {

173 + unclosedCount++

174 continue

175 }

176

@@ -168,6 +178,7 @@ scan:

178 for end > 0 && end < len(input)-1 && input[end-1] == phEscape {

179 nextEnd := strings.Index(input[end+1:], string(phClose))

180 if nextEnd < 0 {

181 + unclosedCount++

182 continue scan

183 }

184 end += nextEnd + 1