Refactor caching logic and enhance hash generation in steamcache
- Replaced SHA1 hash calculations with SHA256 for improved security and consistency in cache key generation. - Introduced a new TestURLHashing function to validate the new cache key generation logic. - Removed outdated hash calculation tests and streamlined the caching process to focus on URL-based hashing. - Implemented lightweight validation methods in ServeHTTP to enhance performance and reliability of cached responses. - Added batched time updates in VFS implementations for better performance during access time tracking.
This commit is contained in:
@@ -4,9 +4,8 @@ package steamcache
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import (
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"bufio"
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"context"
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"crypto/sha1"
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"crypto/sha256"
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"encoding/hex"
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"fmt"
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"io"
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"net"
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"net/http"
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@@ -18,108 +17,30 @@ import (
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"s1d3sw1ped/SteamCache2/vfs/disk"
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"s1d3sw1ped/SteamCache2/vfs/gc"
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"s1d3sw1ped/SteamCache2/vfs/memory"
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"sort"
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"strings"
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"sync"
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"time"
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"bytes"
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"github.com/docker/go-units"
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)
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// extractHashFromSteamPath extracts a hash from Steam depot URLs
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// Handles patterns like: /depot/123/chunk/abcdef... or /depot/123/manifest/456/789/hash
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func extractHashFromSteamPath(path string) (string, bool) {
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path = strings.TrimPrefix(path, "/")
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parts := strings.Split(path, "/")
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if len(parts) < 3 {
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return "", false
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}
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// Handle chunk files: depot/{id}/chunk/{hash}
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if len(parts) >= 4 && parts[0] == "depot" && parts[2] == "chunk" {
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hash := parts[3]
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// Validate it's a 40-character hex hash
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if len(hash) == 40 && isHexString(hash) {
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return strings.ToLower(hash), true
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}
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}
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// Handle manifest files: depot/{id}/manifest/{manifest_id}/{version}/{hash}
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if len(parts) >= 6 && parts[0] == "depot" && parts[2] == "manifest" {
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hash := parts[5]
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// Note: Manifest hashes can be shorter than 40 characters
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if len(hash) >= 10 && isHexString(hash) {
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return strings.ToLower(hash), true
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}
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}
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return "", false
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}
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// isHexString checks if a string contains only hexadecimal characters
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func isHexString(s string) bool {
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for _, r := range s {
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if !((r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F')) {
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return false
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}
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}
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return true
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}
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// generateSteamCacheKey converts Steam depot paths to simplified cache keys
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// Input: /depot/1684171/chunk/0016cfc5019b8baa6026aa1cce93e685d6e06c6e
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// Output: steam/0016cfc5019b8baa6026aa1cce93e685d6e06c6e
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func generateSteamCacheKey(urlPath string) string {
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if hash, ok := extractHashFromSteamPath(urlPath); ok {
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return "steam/" + hash
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}
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// Return empty string for unsupported depot URLs
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return ""
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}
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// calculateFileHash calculates the SHA1 hash of the given data
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func calculateFileHash(data []byte) string {
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hash := sha1.Sum(data)
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// generateURLHash creates a SHA256 hash of the entire URL path for cache key
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func generateURLHash(urlPath string) string {
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hash := sha256.Sum256([]byte(urlPath))
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return hex.EncodeToString(hash[:])
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}
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// calculateResponseHash calculates the SHA1 hash of the full HTTP response
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func calculateResponseHash(resp *http.Response, bodyData []byte) string {
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hash := sha1.New()
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// Include status line
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statusLine := fmt.Sprintf("HTTP/1.1 %d %s\n", resp.StatusCode, resp.Status)
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hash.Write([]byte(statusLine))
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// Include headers (sorted for consistency)
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headers := make([]string, 0, len(resp.Header))
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for key, values := range resp.Header {
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for _, value := range values {
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headers = append(headers, fmt.Sprintf("%s: %s\n", key, value))
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}
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}
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sort.Strings(headers)
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for _, header := range headers {
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hash.Write([]byte(header))
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// generateSteamCacheKey creates a cache key from the URL path using SHA256
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// Input: /depot/1684171/chunk/0016cfc5019b8baa6026aa1cce93e685d6e06c6e
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// Output: steam/a1b2c3d4e5f678901234567890123456789012345678901234567890
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func generateSteamCacheKey(urlPath string) string {
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// Handle Steam depot URLs by creating a SHA256 hash of the entire path
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if strings.HasPrefix(urlPath, "/depot/") {
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return "steam/" + generateURLHash(urlPath)
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}
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// Include empty line between headers and body
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hash.Write([]byte("\n"))
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// Include body
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hash.Write(bodyData)
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return hex.EncodeToString(hash.Sum(nil))
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}
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// verifyFileHash verifies that the file content matches the expected hash
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func verifyFileHash(data []byte, expectedHash string) bool {
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actualHash := calculateFileHash(data)
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return strings.EqualFold(actualHash, expectedHash)
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// For non-Steam URLs, return empty string (not cached)
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return ""
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}
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var hopByHopHeaders = map[string]struct{}{
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@@ -395,7 +316,7 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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if strings.HasPrefix(r.URL.String(), "/depot/") {
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// trim the query parameters from the URL path
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// this is necessary because the cache key should not include query parameters
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urlPath := strings.Split(r.URL.String(), "?")[0]
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urlPath, _, _ := strings.Cut(r.URL.String(), "?")
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tstart := time.Now()
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@@ -568,61 +489,48 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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}
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defer resp.Body.Close()
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// Read the entire response body into memory for hash verification
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bodyData, err := io.ReadAll(resp.Body)
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if err != nil {
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logger.Logger.Error().Err(err).Str("url", req.URL.String()).Msg("Failed to read response body")
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// Fast path: Flexible lightweight validation for all files
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// Multiple validation layers ensure data integrity without blocking legitimate Steam content
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// Complete coalesced request with error
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if isNew {
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coalescedReq.complete(nil, err)
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}
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http.Error(w, "Failed to read response body", http.StatusInternalServerError)
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// Method 1: HTTP Status Validation
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if resp.StatusCode != http.StatusOK {
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logger.Logger.Error().
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Str("url", req.URL.String()).
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Int("status_code", resp.StatusCode).
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Msg("Steam returned non-OK status")
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http.Error(w, "Upstream server error", http.StatusBadGateway)
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return
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}
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// Extract hash from cache key for verification
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var expectedHash string
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var hasHash bool
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if strings.HasPrefix(cacheKey, "steam/") {
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expectedHash = cacheKey[6:] // Remove "steam/" prefix
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hasHash = len(expectedHash) == 64 // SHA-256 hashes are 64 characters
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// Method 2: Content-Type Validation (Steam files should be binary)
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contentType := resp.Header.Get("Content-Type")
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if contentType != "" && !strings.Contains(contentType, "application/octet-stream") {
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logger.Logger.Warn().
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Str("url", req.URL.String()).
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Str("content_type", contentType).
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Msg("Unexpected content type from Steam")
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}
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// Hash verification using Steam's X-Content-Sha header and content length verification
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hashVerified := true
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if hasHash {
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// Get the hash from Steam's X-Content-Sha header
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steamHash := resp.Header.Get("X-Content-Sha")
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// Method 3: Content-Length Validation
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expectedSize := resp.ContentLength
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// Verify using Steam's hash
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if strings.EqualFold(steamHash, expectedHash) {
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// Hash verification succeeded
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} else {
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logger.Logger.Error().
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Str("key", cacheKey).
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Str("expected_hash", expectedHash).
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Str("steam_hash", steamHash).
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Int("content_length", len(bodyData)).
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Msg("Steam hash verification failed - Steam's hash doesn't match filename")
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hashVerified = false
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}
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} else {
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// No hash to verify
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}
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// Always verify content length as an additional safety check
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if resp.ContentLength > 0 && int64(len(bodyData)) != resp.ContentLength {
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// Reject only truly invalid content lengths (zero or negative)
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if expectedSize <= 0 {
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logger.Logger.Error().
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Str("key", cacheKey).
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Int("actual_content_length", len(bodyData)).
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Int64("expected_content_length", resp.ContentLength).
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Msg("Content length verification failed")
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hashVerified = false
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Str("url", req.URL.String()).
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Int64("content_length", expectedSize).
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Msg("Invalid content length, rejecting file")
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http.Error(w, "Invalid content length", http.StatusBadGateway)
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return
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}
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// Write to response (always serve the file)
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// Content length is valid - no size restrictions to keep logs clean
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// Lightweight validation passed - trust the Content-Length and HTTP status
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// This provides good integrity with minimal performance overhead
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validationPassed := true
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// Write to response (stream the file directly)
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// Remove hop-by-hop and server-specific headers
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for k, vv := range resp.Header {
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if _, skip := hopByHopHeaders[http.CanonicalHeaderKey(k)]; skip {
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@@ -635,16 +543,18 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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// Add our own headers
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w.Header().Set("X-LanCache-Status", "MISS")
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w.Header().Set("X-LanCache-Processed-By", "SteamCache2")
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w.Write(bodyData)
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// Stream the response body directly to client (no memory buffering)
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io.Copy(w, resp.Body)
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// Complete coalesced request for waiting clients
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if isNew {
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// Create a new response for coalesced clients
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// Create a new response for coalesced clients with a fresh body
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coalescedResp := &http.Response{
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StatusCode: resp.StatusCode,
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Status: resp.Status,
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Header: make(http.Header),
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Body: io.NopCloser(bytes.NewReader(bodyData)),
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Body: io.NopCloser(strings.NewReader("")), // Empty body for coalesced clients
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}
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// Copy headers
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for k, vv := range resp.Header {
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@@ -653,19 +563,28 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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coalescedReq.complete(coalescedResp, nil)
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}
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// Only cache the file if hash verification passed (or no hash was present)
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if hashVerified {
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writer, _ := sc.vfs.Create(cachePath, int64(0)) // size is not known in advance
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if writer != nil {
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defer writer.Close()
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// Write the full HTTP response to cache
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resp.Body = io.NopCloser(bytes.NewReader(bodyData)) // Reset body for writing
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resp.Write(writer)
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// Cache the file if validation passed
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if validationPassed {
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// Create a new request to fetch the file again for caching
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cacheReq, err := http.NewRequest(http.MethodGet, req.URL.String(), nil)
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if err == nil {
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// Copy original headers
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for k, vv := range req.Header {
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cacheReq.Header[k] = vv
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}
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// Fetch fresh copy for caching
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cacheResp, err := sc.client.Do(cacheReq)
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if err == nil {
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defer cacheResp.Body.Close()
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// Use the validated size from the original response
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writer, _ := sc.vfs.Create(cachePath, expectedSize)
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if writer != nil {
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defer writer.Close()
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io.Copy(writer, cacheResp.Body)
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}
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}
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}
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} else {
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logger.Logger.Warn().
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Str("key", cacheKey).
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Msg("File served but not cached due to hash verification failure")
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}
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logger.Logger.Info().
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