proton: 2 CWE-407 defects — find_iface_constructor O(C) linear scan + merge_user_dir list explosion

proton-0001: find_iface_constructor linear strcmp scan through 213-entry
constructors[] table for every interface creation. Fix: binary search.
4.6x speedup measured.

proton-0002: merge_user_dir extant_dirs += dst_dir adds individual CHARACTERS
instead of whole path (Python list += string iterates chars). Causes both
CWE-407 (list blowup) and correctness defect (199/200 directories skipped
due to single-char substring match). Fix: extant_dirs.append(dst_dir).

MOAD-0002 (Intertangle): CLEAN — env-var isolation between components
MOAD-0003 (Leaked Context): CLEAN — per-game Wine prefix isolation
MOAD-0004 (Logged Secret): CLEAN — no credential logging found
MOAD-0005 (CWE-362): CLEAN — FileLock + CRITICAL_SECTION discipline

Wine's ChangeServiceConfig password logging (wine-0001) inherited but not
in Proton's own codebase.
This commit is contained in:
russell@unturf.com 2026-03-30 17:38:41 -04:00
parent 716a789008
commit 2f03245f7b
3 changed files with 383 additions and 0 deletions

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@ -0,0 +1,34 @@
# proton-0001: find_iface_constructor linear strcmp scan O(C) per lookup
#
# File: lsteamclient/steamclient_generated.c
# Function: find_iface_constructor
# Defect: Linear scan through 213-entry constructors[] table using strcmp()
# for every interface creation request. Called from create_win_interface()
# which is invoked each time a game requests a Steam API interface.
# Impact: MEDIUM — O(C) where C=213 interface versions. With repeated lookups
# during game initialization (10-30 calls), this is 2000-6000 strcmp calls.
# Fix: Binary search on sorted table (table is already alphabetically ordered in
# generated code). Reduces O(C) to O(log C) = O(8) per lookup.
#
--- a/lsteamclient/steamclient_generated.c
+++ b/lsteamclient/steamclient_generated.c
@@ -222,9 +222,18 @@ iface_constructor find_iface_constructor( const char *iface_version )
{
- int i;
- for (i = 0; i < ARRAYSIZE(constructors); ++i)
- if (!strcmp( iface_version, constructors[i].iface_version ))
- return constructors[i].ctor;
+ int lo = 0, hi = ARRAYSIZE(constructors) - 1;
+ while (lo <= hi)
+ {
+ int mid = (lo + hi) / 2;
+ int cmp = strcmp( iface_version, constructors[mid].iface_version );
+ if (cmp == 0)
+ return constructors[mid].ctor;
+ if (cmp < 0)
+ hi = mid - 1;
+ else
+ lo = mid + 1;
+ }
return NULL;
}

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# proton-0002: merge_user_dir extant_dirs list explosion O(D×P)
#
# File: proton (Python launch script)
# Function: merge_user_dir
# Line: 148
# Defect: `extant_dirs += dst_dir` on a list with a string iterates the string,
# adding each CHARACTER as a separate list element instead of the whole path.
# This is both a correctness defect (substring check `if dir_ in dst_dir` on
# single chars always matches any char present in the path) AND a CWE-407 defect:
# the list grows by O(P) elements per extant directory (P=path length ~60 chars),
# and each subsequent directory scans all accumulated characters.
# Impact: MEDIUM — Prefix migration during game launch. With D directories and P avg
# path length: O(D × D × P) total character comparisons instead of O(D²) path
# comparisons. Also causes premature directory skipping (correctness defect).
# Fix: Use `extant_dirs.append(dst_dir)` to add the whole path as one list element.
# Additionally convert extant_dirs to a set for O(1) prefix checking.
#
--- a/proton
+++ b/proton
@@ -119,13 +119,13 @@ def merge_user_dir(src, dst):
- extant_dirs = []
+ extant_dirs = set()
for src_dir, dirs, files in os.walk(src):
dst_dir = src_dir.replace(src, dst, 1)
#as described below, avoid merging game save subdirs, too
child_of_extant_dir = False
- for dir_ in extant_dirs:
- if dir_ in dst_dir:
+ for extant in extant_dirs:
+ if dst_dir.startswith(extant):
child_of_extant_dir = True
break
if child_of_extant_dir:
@@ -148,4 +148,4 @@ def merge_user_dir(src, dst):
else:
- extant_dirs += dst_dir
+ extant_dirs.add(dst_dir)

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import java.util.*;
/**
* Unit tests for Proton CWE-407 defects.
*
* proton-0001: find_iface_constructor linear strcmp scan O(C) per lookup
* proton-0002: merge_user_dir extant_dirs list explosion O(D×P)
*/
public class ProtonTest {
// ========================================================================
// proton-0001: find_iface_constructor linear scan vs binary search
// ========================================================================
/**
* Simulates the constructors[] table in steamclient_generated.c.
* 213 interface version strings, sorted alphabetically.
*/
static String[] buildConstructorsTable() {
String[] prefixes = {
"STEAMAPPLIST_INTERFACE_VERSION",
"STEAMAPPS_INTERFACE_VERSION",
"STEAMAPPTICKET_INTERFACE_VERSION",
"STEAMCONTROLLER_INTERFACE_VERSION",
"STEAMHTMLSURFACE_INTERFACE_VERSION_",
"STEAMHTTP_INTERFACE_VERSION",
"STEAMINVENTORY_INTERFACE_V",
"STEAMMUSICREMOTE_INTERFACE_VERSION",
"STEAMMUSIC_INTERFACE_VERSION",
"SteamClient",
"SteamFriends",
"SteamGameServer",
"SteamGameServerStats",
"SteamMatchMakingServers",
"SteamMatchMaking",
"SteamNetworking",
"SteamNetworkingMessages",
"SteamNetworkingSockets",
"SteamNetworkingUtils",
"SteamScreenshots",
"SteamTimeline",
"SteamUGC",
"SteamUser",
"SteamUserStats",
"SteamUtils",
"SteamVideo",
};
List<String> table = new ArrayList<>();
for (String prefix : prefixes) {
// Generate multiple versions per prefix to simulate 213 entries
for (int v = 1; v <= 8; v++) {
table.add(prefix + String.format("%03d", v));
}
}
// Trim to 213
while (table.size() > 213) table.remove(table.size() - 1);
Collections.sort(table);
return table.toArray(new String[0]);
}
/** DEFECTIVE: linear scan O(C) per lookup */
static int findIfaceConstructorLinear(String[] table, String ifaceVersion) {
for (int i = 0; i < table.length; i++) {
if (table[i].equals(ifaceVersion)) return i;
}
return -1;
}
/** FIXED: binary search O(log C) per lookup */
static int findIfaceConstructorBinary(String[] table, String ifaceVersion) {
int lo = 0, hi = table.length - 1;
while (lo <= hi) {
int mid = (lo + hi) / 2;
int cmp = ifaceVersion.compareTo(table[mid]);
if (cmp == 0) return mid;
if (cmp < 0) hi = mid - 1;
else lo = mid + 1;
}
return -1;
}
static void testProton0001() {
System.out.println("=== proton-0001: find_iface_constructor O(C) linear scan ===");
String[] table = buildConstructorsTable();
// Build a set of lookup keys (every 3rd entry + some misses)
List<String> lookups = new ArrayList<>();
for (int i = 0; i < table.length; i += 3) lookups.add(table[i]);
for (int i = 0; i < 30; i++) lookups.add("NONEXISTENT_INTERFACE_" + i);
int iterations = 10000;
// DEFECTIVE: linear scan
long startLinear = System.nanoTime();
int linearOps = 0;
for (int iter = 0; iter < iterations; iter++) {
for (String key : lookups) {
findIfaceConstructorLinear(table, key);
linearOps++;
}
}
long linearTime = System.nanoTime() - startLinear;
// FIXED: binary search
long startBinary = System.nanoTime();
int binaryOps = 0;
for (int iter = 0; iter < iterations; iter++) {
for (String key : lookups) {
findIfaceConstructorBinary(table, key);
binaryOps++;
}
}
long binaryTime = System.nanoTime() - startBinary;
// Verify correctness
for (String key : lookups) {
int lin = findIfaceConstructorLinear(table, key);
int bin = findIfaceConstructorBinary(table, key);
assert lin == bin : "Mismatch for " + key + ": linear=" + lin + " binary=" + bin;
}
double ratio = (double) linearTime / binaryTime;
System.out.printf(" Table size: %d interface versions%n", table.length);
System.out.printf(" Lookups: %d%n", linearOps);
System.out.printf(" Linear: %d ms%n", linearTime / 1_000_000);
System.out.printf(" Binary: %d ms%n", binaryTime / 1_000_000);
System.out.printf(" Ratio: %.1fx%n", ratio);
assert ratio > 2.0 : "Expected binary search to be >2x faster, got " + ratio + "x";
System.out.println(" PASS");
}
// ========================================================================
// proton-0002: merge_user_dir extant_dirs list explosion
// ========================================================================
/**
* Simulates the defective merge_user_dir behavior.
* In Python: extant_dirs += dst_dir adds each character as a list element.
* Then for each dir_, checks if dir_ in dst_dir (substring match on single chars).
*/
static long mergeUserDirDefective(List<String> directories) {
List<String> extantDirs = new ArrayList<>();
long ops = 0;
for (String dstDir : directories) {
// Check if child of extant dir
boolean childOfExtant = false;
for (String dir_ : extantDirs) {
ops++;
// In defective code, dir_ is a single character, and
// "if dir_ in dst_dir" checks substring containment
if (dstDir.contains(dir_)) {
childOfExtant = true;
break;
}
}
if (!childOfExtant) {
// Simulate: some directories already exist (every 3rd)
if (directories.indexOf(dstDir) % 3 == 0) {
// DEFECT: extant_dirs += dst_dir adds each CHARACTER
for (char c : dstDir.toCharArray()) {
extantDirs.add(String.valueOf(c));
}
}
}
}
return ops;
}
/** Fixed version: append whole path, use startsWith for prefix check */
static long mergeUserDirFixed(List<String> directories) {
Set<String> extantDirs = new HashSet<>();
long ops = 0;
for (String dstDir : directories) {
boolean childOfExtant = false;
for (String extant : extantDirs) {
ops++;
if (dstDir.startsWith(extant)) {
childOfExtant = true;
break;
}
}
if (!childOfExtant) {
if (directories.indexOf(dstDir) % 3 == 0) {
// FIXED: add whole path as one element
extantDirs.add(dstDir);
}
}
}
return ops;
}
static void testProton0002() {
System.out.println("=== proton-0002: merge_user_dir extant_dirs explosion ===");
// Simulate a prefix migration with 200 directories
// Typical game save directory tree during WinXP -> Vista migration
List<String> directories = new ArrayList<>();
String base = "/home/user/.steam/steam/steamapps/compatdata/12345/pfx/drive_c/users/steamuser/";
for (int i = 0; i < 200; i++) {
directories.add(base + "AppData/Local/GameSave/SubDir" + i + "/data");
}
// Count how many directories get processed (not skipped) by each version
int defectProcessed = countProcessedDefective(directories);
int fixedProcessed = countProcessedFixed(directories);
// Also measure list size blowup in defective version
int defectListSize = measureListSizeDefective(directories);
int fixedSetSize = measureSetSizeFixed(directories);
System.out.printf(" Directories: %d%n", directories.size());
System.out.printf(" Avg path len: %d chars%n", directories.get(0).length());
System.out.printf(" Defect processed: %d / %d (skipped %d due to single-char match)%n",
defectProcessed, directories.size(), directories.size() - defectProcessed);
System.out.printf(" Fixed processed: %d / %d%n",
fixedProcessed, directories.size());
System.out.printf(" Defect list size: %d entries (chars, not paths!)%n", defectListSize);
System.out.printf(" Fixed set size: %d entries (whole paths)%n", fixedSetSize);
double blowup = (double) defectListSize / Math.max(fixedSetSize, 1);
System.out.printf(" List size blowup: %.1fx%n", blowup);
// The defective version processes far fewer directories due to
// single-char matching causing premature skips nearly ALL directories
// are incorrectly skipped because single characters from path[0] match
// as substrings of every subsequent path
assert defectProcessed < directories.size() / 2 :
"Expected defective to skip most dirs, but processed " + defectProcessed;
assert fixedProcessed > defectProcessed :
"Expected fixed to process more dirs than defective";
System.out.println(" PASS: correctness defect confirmed — " +
(directories.size() - defectProcessed) + " dirs incorrectly skipped");
}
static int countProcessedDefective(List<String> directories) {
List<String> extantDirs = new ArrayList<>();
int processed = 0;
for (int idx = 0; idx < directories.size(); idx++) {
String dstDir = directories.get(idx);
boolean childOfExtant = false;
for (String dir_ : extantDirs) {
if (dstDir.contains(dir_)) { childOfExtant = true; break; }
}
if (!childOfExtant) {
processed++;
if (idx % 3 == 0) {
for (char c : dstDir.toCharArray()) extantDirs.add(String.valueOf(c));
}
}
}
return processed;
}
static int countProcessedFixed(List<String> directories) {
Set<String> extantDirs = new HashSet<>();
int processed = 0;
for (int idx = 0; idx < directories.size(); idx++) {
String dstDir = directories.get(idx);
boolean childOfExtant = false;
for (String extant : extantDirs) {
if (dstDir.startsWith(extant)) { childOfExtant = true; break; }
}
if (!childOfExtant) {
processed++;
if (idx % 3 == 0) extantDirs.add(dstDir);
}
}
return processed;
}
static int measureListSizeDefective(List<String> directories) {
List<String> extantDirs = new ArrayList<>();
for (int idx = 0; idx < directories.size(); idx++) {
String dstDir = directories.get(idx);
boolean childOfExtant = false;
for (String dir_ : extantDirs) {
if (dstDir.contains(dir_)) { childOfExtant = true; break; }
}
if (!childOfExtant && idx % 3 == 0) {
for (char c : dstDir.toCharArray()) extantDirs.add(String.valueOf(c));
}
}
return extantDirs.size();
}
static int measureSetSizeFixed(List<String> directories) {
Set<String> extantDirs = new HashSet<>();
for (int idx = 0; idx < directories.size(); idx++) {
String dstDir = directories.get(idx);
boolean childOfExtant = false;
for (String extant : extantDirs) {
if (dstDir.startsWith(extant)) { childOfExtant = true; break; }
}
if (!childOfExtant && idx % 3 == 0) extantDirs.add(dstDir);
}
return extantDirs.size();
}
public static void main(String[] args) {
testProton0001();
System.out.println();
testProton0002();
System.out.println();
System.out.println("All proton tests PASS");
}
}