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Merged
merged 2 commits into from
Jul 18, 2023
Merged

Disallow dangerous URL schemes (#25960) #25964

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4c9ed01
Disallow dangerous url schemes (#25960)
KN4CK3R Jul 18, 2023
69221ca
tidy
KN4CK3R Jul 18, 2023
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2 changes: 1 addition & 1 deletion go.mod
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ require (
github.com/mattn/go-sqlite3 v1.14.16
github.com/meilisearch/meilisearch-go v0.24.0
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 v7.0.52
github.com/minio/sha256-simd v1.0.0
github.com/msteinert/pam v1.1.0
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4 changes: 2 additions & 2 deletions go.sum
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Original file line number Diff line number Diff line change
Expand Up @@ -877,8 +877,8 @@ github.com/mholt/acmez v1.1.0 h1:IQ9CGHKOHokorxnffsqDvmmE30mDenO1lptYZ1AYkHY=
github.com/mholt/acmez v1.1.0/go.mod h1:zwo5+fbLLTowAX8o8ETfQzbDtwGEXnPhkmGdKIP+bgs=
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 v1.1.54 h1:5jon9mWcb0sFJGpnI99tOMhCPyJ+RPVz5b63MQG0VWI=
github.com/miekg/dns v1.1.54/go.mod h1:uInx36IzPl7FYnDcMeVWxj9byh7DutNykX4G9Sj60FY=
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9 changes: 9 additions & 0 deletions modules/markup/sanitizer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ package markup

import (
"io"
"net/url"
"regexp"
"sync"

Expand Down Expand Up @@ -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
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9 changes: 7 additions & 2 deletions modules/markup/sanitizer_test.go
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Expand Up @@ -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 {
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