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Disallow dangerous url schemes (#25960)

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Regression: https://github.com/go-gitea/gitea/pull/24805
Closes: #25945

- Disallow `javascript`, `vbscript` and `data` (data uri images still
work) url schemes even if all other schemes are allowed
- Fixed older `cbthunderlink` tests

---------

Co-authored-by: delvh <dev.lh@web.de>
This commit is contained in:
KN4CK3R 2023-07-18 17:18:37 +02:00 • committed by GitHub
parent cc73e84fa3
commit 8af96f585f
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4 changed files with 19 additions and 5 deletions
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2
go.mod
View file

@ -76,7 +76,7 @@ require (
github.com/mattn/go-sqlite3 v1.14.17
github.com/meilisearch/meilisearch-go v0.25.0
github.com/mholt/archiver/v3 v3.5.1
github.com/microcosm-cc/bluemonday v1.0.24
github.com/microcosm-cc/bluemonday v1.0.25
github.com/minio/minio-go/v7 v7.0.60
github.com/minio/sha256-simd v1.0.1
github.com/msteinert/pam v1.1.0

4
go.sum
View file

@ -865,8 +865,8 @@ github.com/mholt/acmez v1.2.0 h1:1hhLxSgY5FvH5HCnGUuwbKY2VQVo8IU7rxXKSnZ7F30=
github.com/mholt/acmez v1.2.0/go.mod h1:VT9YwH1xgNX1kmYY89gY8xPJC84BFAisjo8Egigt4kE=
github.com/mholt/archiver/v3 v3.5.1 h1:rDjOBX9JSF5BvoJGvjqK479aL70qh9DIpZCl+k7Clwo=
github.com/mholt/archiver/v3 v3.5.1/go.mod h1:e3dqJ7H78uzsRSEACH1joayhuSyhnonssnDhppzS1L4=
github.com/microcosm-cc/bluemonday v1.0.24 h1:NGQoPtwGVcbGkKfvyYk1yRqknzBuoMiUrO6R7uFTPlw=
github.com/microcosm-cc/bluemonday v1.0.24/go.mod h1:ArQySAMps0790cHSkdPEJ7bGkF2VePWH773hsJNSHf8=
github.com/microcosm-cc/bluemonday v1.0.25 h1:4NEwSfiJ+Wva0VxN5B8OwMicaJvD8r9tlJWm9rtloEg=
github.com/microcosm-cc/bluemonday v1.0.25/go.mod h1:ZIOjCQp1OrzBBPIJmfX4qDYFuhU02nx4bn030ixfHLE=
github.com/miekg/dns v1.0.14/go.mod h1:W1PPwlIAgtquWBMBEV9nkV9Cazfe8ScdGz/Lj7v3Nrg=
github.com/miekg/dns v1.1.55 h1:GoQ4hpsj0nFLYe+bWiCToyrBEJXkQfOOIvFGFy0lEgo=
github.com/miekg/dns v1.1.55/go.mod h1:uInx36IzPl7FYnDcMeVWxj9byh7DutNykX4G9Sj60FY=

9
modules/markup/sanitizer.go
View file

@ -6,6 +6,7 @@ package markup
import (
"io"
"net/url"
"regexp"
"sync"
@ -79,6 +80,14 @@ func createDefaultPolicy() *bluemonday.Policy {
policy.AllowURLSchemes(setting.Markdown.CustomURLSchemes...)
} else {
policy.AllowURLSchemesMatching(allowAllRegex)
// Even if every scheme is allowed, these three are blocked for security reasons
disallowScheme := func(*url.URL) bool {
return false
}
policy.AllowURLSchemeWithCustomPolicy("javascript", disallowScheme)
policy.AllowURLSchemeWithCustomPolicy("vbscript", disallowScheme)
policy.AllowURLSchemeWithCustomPolicy("data", disallowScheme)
}
// Allow classes for anchors

9
modules/markup/sanitizer_test.go
View file

@ -54,8 +54,13 @@ func Test_Sanitizer(t *testing.T) {
`<code style="bad-color: red">Hello World</code>`, `<code>Hello World</code>`,
// URLs
`[my custom URL scheme](cbthunderlink://somebase64string)`, `[my custom URL scheme](cbthunderlink://somebase64string)`,
`[my custom URL scheme](matrix:roomid/psumPMeAfzgAeQpXMG:feneas.org?action=join)`, `[my custom URL scheme](matrix:roomid/psumPMeAfzgAeQpXMG:feneas.org?action=join)`,
`<a href="cbthunderlink://somebase64string)">my custom URL scheme</a>`, `<a href="cbthunderlink://somebase64string)" rel="nofollow">my custom URL scheme</a>`,
`<a href="matrix:roomid/psumPMeAfzgAeQpXMG:feneas.org?action=join">my custom URL scheme</a>`, `<a href="matrix:roomid/psumPMeAfzgAeQpXMG:feneas.org?action=join" rel="nofollow">my custom URL scheme</a>`,
// Disallow dangerous url schemes
`<a href="javascript:alert('xss')">bad</a>`, `bad`,
`<a href="vbscript:no">bad</a>`, `bad`,
`<a href="data:1234">bad</a>`, `bad`,
}
for i := 0; i < len(testCases); i += 2 {