1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
|
// Copyright 2011 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.
package template
import (
"fmt"
"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
)
// Error describes a problem encountered during template Escaping.
type Error struct {
// ErrorCode describes the kind of error.
ErrorCode ErrorCode
// Node is the node that caused the problem, if known.
// If not nil, it overrides Name and Line.
Node parse.Node
// Name is the name of the template in which the error was encountered.
Name string
// Line is the line number of the error in the template source or 0.
Line int
// Description is a human-readable description of the problem.
Description string
}
// ErrorCode is a code for a kind of error.
type ErrorCode int
// We define codes for each error that manifests while escaping templates, but
// escaped templates may also fail at runtime.
//
// Output: "ZgotmplZ"
// Example:
//
// <img src="{{.X}}">
// where {{.X}} evaluates to `javascript:...`
//
// Discussion:
//
// "ZgotmplZ" is a special value that indicates that unsafe content reached a
// CSS or URL context at runtime. The output of the example will be
// <img src="#ZgotmplZ">
// If the data comes from a trusted source, use content types to exempt it
// from filtering: URL(`javascript:...`).
const (
// OK indicates the lack of an error.
OK ErrorCode = iota
// ErrAmbigContext: "... appears in an ambiguous context within a URL"
// Example:
// <a href="
// {{if .C}}
// /path/
// {{else}}
// /search?q=
// {{end}}
// {{.X}}
// ">
// Discussion:
// {{.X}} is in an ambiguous URL context since, depending on {{.C}},
// it may be either a URL suffix or a query parameter.
// Moving {{.X}} into the condition removes the ambiguity:
// <a href="{{if .C}}/path/{{.X}}{{else}}/search?q={{.X}}">
ErrAmbigContext
// ErrBadHTML: "expected space, attr name, or end of tag, but got ...",
// "... in unquoted attr", "... in attribute name"
// Example:
// <a href = /search?q=foo>
// <href=foo>
// <form na<e=...>
// <option selected<
// Discussion:
// This is often due to a typo in an HTML element, but some runes
// are banned in tag names, attribute names, and unquoted attribute
// values because they can tickle parser ambiguities.
// Quoting all attributes is the best policy.
ErrBadHTML
// ErrBranchEnd: "{{if}} branches end in different contexts"
// Example:
// {{if .C}}<a href="{{end}}{{.X}}
// Discussion:
// Package html/template statically examines each path through an
// {{if}}, {{range}}, or {{with}} to escape any following pipelines.
// The example is ambiguous since {{.X}} might be an HTML text node,
// or a URL prefix in an HTML attribute. The context of {{.X}} is
// used to figure out how to escape it, but that context depends on
// the run-time value of {{.C}} which is not statically known.
//
// The problem is usually something like missing quotes or angle
// brackets, or can be avoided by refactoring to put the two contexts
// into different branches of an if, range or with. If the problem
// is in a {{range}} over a collection that should never be empty,
// adding a dummy {{else}} can help.
ErrBranchEnd
// ErrEndContext: "... ends in a non-text context: ..."
// Examples:
// <div
// <div title="no close quote>
// <script>f()
// Discussion:
// Executed templates should produce a DocumentFragment of HTML.
// Templates that end without closing tags will trigger this error.
// Templates that should not be used in an HTML context or that
// produce incomplete Fragments should not be executed directly.
//
// {{define "main"}} <script>{{template "helper"}}</script> {{end}}
// {{define "helper"}} document.write(' <div title=" ') {{end}}
//
// "helper" does not produce a valid document fragment, so should
// not be Executed directly.
ErrEndContext
// ErrNoSuchTemplate: "no such template ..."
// Examples:
// {{define "main"}}<div {{template "attrs"}}>{{end}}
// {{define "attrs"}}href="{{.URL}}"{{end}}
// Discussion:
// Package html/template looks through template calls to compute the
// context.
// Here the {{.URL}} in "attrs" must be treated as a URL when called
// from "main", but you will get this error if "attrs" is not defined
// when "main" is parsed.
ErrNoSuchTemplate
// ErrOutputContext: "cannot compute output context for template ..."
// Examples:
// {{define "t"}}{{if .T}}{{template "t" .T}}{{end}}{{.H}}",{{end}}
// Discussion:
// A recursive template does not end in the same context in which it
// starts, and a reliable output context cannot be computed.
// Look for typos in the named template.
// If the template should not be called in the named start context,
// look for calls to that template in unexpected contexts.
// Maybe refactor recursive templates to not be recursive.
ErrOutputContext
// ErrPartialCharset: "unfinished JS regexp charset in ..."
// Example:
// <script>var pattern = /foo[{{.Chars}}]/</script>
// Discussion:
// Package html/template does not support interpolation into regular
// expression literal character sets.
ErrPartialCharset
// ErrPartialEscape: "unfinished escape sequence in ..."
// Example:
// <script>alert("\{{.X}}")</script>
// Discussion:
// Package html/template does not support actions following a
// backslash.
// This is usually an error and there are better solutions; for
// example
// <script>alert("{{.X}}")</script>
// should work, and if {{.X}} is a partial escape sequence such as
// "xA0", mark the whole sequence as safe content: JSStr(`\xA0`)
ErrPartialEscape
// ErrRangeLoopReentry: "on range loop re-entry: ..."
// Example:
// <script>var x = [{{range .}}'{{.}},{{end}}]</script>
// Discussion:
// If an iteration through a range would cause it to end in a
// different context than an earlier pass, there is no single context.
// In the example, there is missing a quote, so it is not clear
// whether {{.}} is meant to be inside a JS string or in a JS value
// context. The second iteration would produce something like
//
// <script>var x = ['firstValue,'secondValue]</script>
ErrRangeLoopReentry
// ErrSlashAmbig: '/' could start a division or regexp.
// Example:
// <script>
// {{if .C}}var x = 1{{end}}
// /-{{.N}}/i.test(x) ? doThis : doThat();
// </script>
// Discussion:
// The example above could produce `var x = 1/-2/i.test(s)...`
// in which the first '/' is a mathematical division operator or it
// could produce `/-2/i.test(s)` in which the first '/' starts a
// regexp literal.
// Look for missing semicolons inside branches, and maybe add
// parentheses to make it clear which interpretation you intend.
ErrSlashAmbig
// ErrPredefinedEscaper: "predefined escaper ... disallowed in template"
// Example:
// <div class={{. | html}}>Hello<div>
// Discussion:
// Package html/template already contextually escapes all pipelines to
// produce HTML output safe against code injection. Manually escaping
// pipeline output using the predefined escapers "html" or "urlquery" is
// unnecessary, and may affect the correctness or safety of the escaped
// pipeline output in Go 1.8 and earlier.
//
// In most cases, such as the given example, this error can be resolved by
// simply removing the predefined escaper from the pipeline and letting the
// contextual autoescaper handle the escaping of the pipeline. In other
// instances, where the predefined escaper occurs in the middle of a
// pipeline where subsequent commands expect escaped input, e.g.
// {{.X | html | makeALink}}
// where makeALink does
// return `<a href="`+input+`">link</a>`
// consider refactoring the surrounding template to make use of the
// contextual autoescaper, i.e.
// <a href="{{.X}}">link</a>
//
// To ease migration to Go 1.9 and beyond, "html" and "urlquery" will
// continue to be allowed as the last command in a pipeline. However, if the
// pipeline occurs in an unquoted attribute value context, "html" is
// disallowed. Avoid using "html" and "urlquery" entirely in new templates.
ErrPredefinedEscaper
// ErrJSTemplate: "... appears in a JS template literal"
// Example:
// <script>var tmpl = `{{.Interp}}`</script>
// Discussion:
// Package html/template does not support actions inside of JS template
// literals.
ErrJSTemplate
)
func (e *Error) Error() string {
switch {
case e.Node != nil:
loc, _ := (*parse.Tree)(nil).ErrorContext(e.Node)
return fmt.Sprintf("html/template:%s: %s", loc, e.Description)
case e.Line != 0:
return fmt.Sprintf("html/template:%s:%d: %s", e.Name, e.Line, e.Description)
case e.Name != "":
return fmt.Sprintf("html/template:%s: %s", e.Name, e.Description)
}
return "html/template: " + e.Description
}
// errorf creates an error given a format string f and args.
// The template Name still needs to be supplied.
func errorf(k ErrorCode, node parse.Node, line int, f string, args ...any) *Error {
return &Error{k, node, "", line, fmt.Sprintf(f, args...)}
}
|