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https://github.com/securego/gosec.git
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Cosmin Cojocar
e7ea2377aa
Add taint analysis rule G708 to detect SSTI vulnerabilities when using Go text/template package. Covers two attack vectors: - User input flowing into Template.Parse() (SSTI/RCE) - Tainted data passed to Execute/ExecuteTemplate with http.ResponseWriter (XSS) CWE-94. Includes 6 test samples (3 positive, 3 negative).
105 lines
3.8 KiB
Go
105 lines
3.8 KiB
Go
// (c) Copyright gosec's authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package analyzers
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import (
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"golang.org/x/tools/go/analysis"
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"github.com/securego/gosec/v2/taint"
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)
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// SSTI returns a configuration for detecting Server-Side Template Injection
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// vulnerabilities via text/template.
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//
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// The text/template package performs NO auto-escaping and allows calling any
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// exported method on the data object passed to Execute. When user-controlled
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// input flows into Template.Parse, an attacker can invoke arbitrary methods,
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// read files, or achieve remote code execution depending on available gadgets.
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//
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// Even when the template string is static, rendering user data through
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// text/template into an HTTP response produces unescaped HTML, enabling XSS.
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func SSTI() taint.Config {
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return taint.Config{
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Sources: []taint.Source{
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// Type sources: tainted when received as parameters
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{Package: "net/http", Name: "Request", Pointer: true},
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{Package: "net/url", Name: "Values"},
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// Function sources
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{Package: "os", Name: "Args", IsFunc: true},
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{Package: "os", Name: "Getenv", IsFunc: true},
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// I/O sources
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{Package: "bufio", Name: "Reader", Pointer: true},
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{Package: "bufio", Name: "Scanner", Pointer: true},
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},
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Sinks: []taint.Sink{
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// CRITICAL: user input flows into the template string itself.
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// Template.Parse takes a single string argument (the template text).
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{Package: "text/template", Receiver: "Template", Method: "Parse", Pointer: true, CheckArgs: []int{1}},
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// text/template.Must wraps Parse; arg[0] is the (*Template, error) pair
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// but in practice the taint flows through the Parse call above.
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// HIGH: text/template.Execute writes unescaped output to an HTTP response.
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// Guard: only flag when the writer (arg 1) implements net/http.ResponseWriter.
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{
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Package: "text/template",
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Receiver: "Template",
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Method: "Execute",
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Pointer: true,
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CheckArgs: []int{2},
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ArgTypeGuards: map[int]string{1: "net/http.ResponseWriter"},
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},
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{
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Package: "text/template",
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Receiver: "Template",
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Method: "ExecuteTemplate",
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Pointer: true,
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CheckArgs: []int{3},
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ArgTypeGuards: map[int]string{1: "net/http.ResponseWriter"},
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},
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},
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Sanitizers: []taint.Sanitizer{
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// HTML escaping neutralizes both SSTI template directives and XSS payloads
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{Package: "html", Method: "EscapeString"},
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{Package: "html/template", Method: "HTMLEscapeString"},
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{Package: "html/template", Method: "JSEscapeString"},
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{Package: "net/url", Method: "QueryEscape"},
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{Package: "net/url", Method: "PathEscape"},
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// Numeric conversions produce safe output
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{Package: "strconv", Method: "Atoi"},
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{Package: "strconv", Method: "Itoa"},
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{Package: "strconv", Method: "ParseInt"},
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{Package: "strconv", Method: "ParseUint"},
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{Package: "strconv", Method: "ParseFloat"},
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{Package: "strconv", Method: "FormatInt"},
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{Package: "strconv", Method: "FormatUint"},
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{Package: "strconv", Method: "FormatFloat"},
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},
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}
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}
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// newSSTIAnalyzer creates an analyzer for detecting Server-Side Template
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// Injection vulnerabilities via taint analysis (G708).
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func newSSTIAnalyzer(id string, description string) *analysis.Analyzer {
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config := SSTI()
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rule := SSTIRule
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rule.ID = id
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rule.Description = description
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return taint.NewGosecAnalyzer(&rule, &config)
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}
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