42 lines
1.6 KiB
Go
42 lines
1.6 KiB
Go
// Vikunja is a to-do list application to facilitate your life.
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// Copyright 2018-present Vikunja and contributors. All rights reserved.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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package notifications
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import "strings"
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// markdownSpecialChars is the full CommonMark §2.4 backslash-escapable set.
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// '<' is included to neutralize autolinks (`<https://evil.com>`), which
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// bluemonday's UGC policy would otherwise render as clickable <a> tags.
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// '\' is handled separately first so inserted backslashes are not re-escaped.
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const markdownSpecialChars = "`*_{}[]()<>#+-.!|~"
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// EscapeMarkdown escapes every CommonMark-special character in s. Fixes
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// GHSA-45q4-x4r9-8fqj (Markdown injection in notification emails).
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func EscapeMarkdown(s string) string {
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// Backslash first so inserted backslashes are not double-escaped.
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s = strings.ReplaceAll(s, `\`, `\\`)
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var b strings.Builder
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b.Grow(len(s))
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for _, r := range s {
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if r < 128 && strings.ContainsRune(markdownSpecialChars, r) {
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b.WriteByte('\\')
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}
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b.WriteRune(r)
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}
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return b.String()
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}
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