From 351c15d28e0444fd8a78c510a0c4d62ed433c758 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 7 Aug 2024 00:21:12 +0200 Subject: Genesis commit --- vendor/github.com/a-h/templ/safehtml/style.go | 168 ++++++++++++++++++++++++++ 1 file changed, 168 insertions(+) create mode 100644 vendor/github.com/a-h/templ/safehtml/style.go (limited to 'vendor/github.com/a-h/templ/safehtml') diff --git a/vendor/github.com/a-h/templ/safehtml/style.go b/vendor/github.com/a-h/templ/safehtml/style.go new file mode 100644 index 0000000..486df7c --- /dev/null +++ b/vendor/github.com/a-h/templ/safehtml/style.go @@ -0,0 +1,168 @@ +// Adapted from https://raw.githubusercontent.com/google/safehtml/3c4cd5b5d8c9a6c5882fba099979e9f50b65c876/style.go + +// Copyright (c) 2017 The Go Authors. All rights reserved. +// +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file or at +// https://developers.google.com/open-source/licenses/bsd + +package safehtml + +import ( + "net/url" + "regexp" + "strings" +) + +// SanitizeCSS attempts to sanitize CSS properties. +func SanitizeCSS(property, value string) (string, string) { + property = SanitizeCSSProperty(property) + if property == InnocuousPropertyName { + return InnocuousPropertyName, InnocuousPropertyValue + } + return property, SanitizeCSSValue(property, value) +} + +func SanitizeCSSValue(property, value string) string { + if sanitizer, ok := cssPropertyNameToValueSanitizer[property]; ok { + return sanitizer(value) + } + return sanitizeRegular(value) +} + +func SanitizeCSSProperty(property string) string { + if !identifierPattern.MatchString(property) { + return InnocuousPropertyName + } + return strings.ToLower(property) +} + +// identifierPattern matches a subset of valid values defined in +// https://www.w3.org/TR/css-syntax-3/#ident-token-diagram. This pattern matches all generic family name +// keywords defined in https://drafts.csswg.org/css-fonts-3/#family-name-value. +var identifierPattern = regexp.MustCompile(`^[-a-zA-Z]+$`) + +var cssPropertyNameToValueSanitizer = map[string]func(string) string{ + "background-image": sanitizeBackgroundImage, + "font-family": sanitizeFontFamily, + "display": sanitizeEnum, + "background-color": sanitizeRegular, + "background-position": sanitizeRegular, + "background-repeat": sanitizeRegular, + "background-size": sanitizeRegular, + "color": sanitizeRegular, + "height": sanitizeRegular, + "width": sanitizeRegular, + "left": sanitizeRegular, + "right": sanitizeRegular, + "top": sanitizeRegular, + "bottom": sanitizeRegular, + "font-weight": sanitizeRegular, + "padding": sanitizeRegular, + "z-index": sanitizeRegular, +} + +var validURLPrefixes = []string{ + `url("`, + `url('`, + `url(`, +} + +var validURLSuffixes = []string{ + `")`, + `')`, + `)`, +} + +func sanitizeBackgroundImage(v string) string { + // Check for <> as per https://github.com/google/safehtml/blob/be23134998433fcf0135dda53593fc8f8bf4df7c/style.go#L87C2-L89C3 + if strings.ContainsAny(v, "<>") { + return InnocuousPropertyValue + } + for _, u := range strings.Split(v, ",") { + u = strings.TrimSpace(u) + var found bool + for i, prefix := range validURLPrefixes { + if strings.HasPrefix(u, prefix) && strings.HasSuffix(u, validURLSuffixes[i]) { + found = true + u = strings.TrimPrefix(u, validURLPrefixes[i]) + u = strings.TrimSuffix(u, validURLSuffixes[i]) + break + } + } + if !found || !urlIsSafe(u) { + return InnocuousPropertyValue + } + } + return v +} + +func urlIsSafe(s string) bool { + u, err := url.Parse(s) + if err != nil { + return false + } + if u.IsAbs() { + if strings.EqualFold(u.Scheme, "http") || strings.EqualFold(u.Scheme, "https") || strings.EqualFold(u.Scheme, "mailto") { + return true + } + return false + } + return true +} + +var genericFontFamilyName = regexp.MustCompile(`^[a-zA-Z][- a-zA-Z]+$`) + +func sanitizeFontFamily(s string) string { + for _, f := range strings.Split(s, ",") { + f = strings.TrimSpace(f) + if strings.HasPrefix(f, `"`) { + if !strings.HasSuffix(f, `"`) { + return InnocuousPropertyValue + } + continue + } + if !genericFontFamilyName.MatchString(f) { + return InnocuousPropertyValue + } + } + return s +} + +func sanitizeEnum(s string) string { + if !safeEnumPropertyValuePattern.MatchString(s) { + return InnocuousPropertyValue + } + return s +} + +func sanitizeRegular(s string) string { + if !safeRegularPropertyValuePattern.MatchString(s) { + return InnocuousPropertyValue + } + return s +} + +// InnocuousPropertyName is an innocuous property generated by a sanitizer when its input is unsafe. +const InnocuousPropertyName = "zTemplUnsafeCSSPropertyName" + +// InnocuousPropertyValue is an innocuous property generated by a sanitizer when its input is unsafe. +const InnocuousPropertyValue = "zTemplUnsafeCSSPropertyValue" + +// safeRegularPropertyValuePattern matches strings that are safe to use as property values. +// Specifically, it matches string where every '*' or '/' is followed by end-of-text or a safe rune +// (i.e. alphanumerics or runes in the set [+-.!#%_ \t]). This regex ensures that the following +// are disallowed: +// - "/*" and "*/", which are CSS comment markers. +// - "//", even though this is not a comment marker in the CSS specification. Disallowing +// this string minimizes the chance that browser peculiarities or parsing bugs will allow +// sanitization to be bypassed. +// - '(' and ')', which can be used to call functions. +// - ',', since it can be used to inject extra values into a property. +// - Runes which could be matched on CSS error recovery of a previously malformed token, such as '@' +// and ':'. See http://www.w3.org/TR/css3-syntax/#error-handling. +var safeRegularPropertyValuePattern = regexp.MustCompile(`^(?:[*/]?(?:[0-9a-zA-Z+-.!#%_ \t]|$))*$`) + +// safeEnumPropertyValuePattern matches strings that are safe to use as enumerated property values. +// Specifically, it matches strings that contain only alphabetic and '-' runes. +var safeEnumPropertyValuePattern = regexp.MustCompile(`^[a-zA-Z-]*$`) -- cgit v1.2.3