From a17f86ce3a67dd2dab2329d7262bc4ad4e7c37ff Mon Sep 17 00:00:00 2001
From: Guillaume Maudoux <guillaume.maudoux@uclouvain.be>
Date: Thu, 28 Feb 2019 23:26:07 +0100
Subject: [PATCH] Obfuscate memory roots for non-root users

---
 src/libstore/gc.cc           | 14 +++++++-------
 src/nix-daemon/nix-daemon.cc | 11 +++++++++--
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index ecfa5e1ed..73630f36d 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -374,7 +374,8 @@ try_again:
         goto try_again;
     }
     if (res > 0 && buf[0] == '/')
-        roots.emplace(file, std::string(static_cast<char *>(buf), res));
+        roots.emplace((format("{memory:%1%") % file).str(),
+                std::string(static_cast<char *>(buf), res));
     return;
 }
 
@@ -407,8 +408,8 @@ void LocalStore::findRuntimeRoots(Roots & roots)
         while (errno = 0, ent = readdir(procDir.get())) {
             checkInterrupt();
             if (std::regex_match(ent->d_name, digitsRegex)) {
-                readProcLink((format("/proc/%1%/exe") % ent->d_name).str(), unchecked);
-                readProcLink((format("/proc/%1%/cwd") % ent->d_name).str(), unchecked);
+                readProcLink((format("{memory:/proc/%1%/exe}") % ent->d_name).str(), unchecked);
+                readProcLink((format("{memory:/proc/%1%/cwd}") % ent->d_name).str(), unchecked);
 
                 auto fdStr = (format("/proc/%1%/fd") % ent->d_name).str();
                 auto fdDir = AutoCloseDir(opendir(fdStr.c_str()));
@@ -435,10 +436,9 @@ void LocalStore::findRuntimeRoots(Roots & roots)
                     auto mapLines = tokenizeString<std::vector<string>>(readFile(mapFile, true), "\n");
                     int n = 0;
                     for (const auto& line : mapLines) {
-                        n++;
                         auto match = std::smatch{};
                         if (std::regex_match(line, match, mapRegex))
-                            unchecked.emplace((format("{%1%:%2%}") % mapFile % n).str(), match[1]);
+                            unchecked.emplace((format("{memory:%1%:%2%}") % mapFile % n++).str(), match[1]);
                     }
 
                     auto envFile = (format("/proc/%1%/environ") % ent->d_name).str();
@@ -446,7 +446,7 @@ void LocalStore::findRuntimeRoots(Roots & roots)
                     auto env_end = std::sregex_iterator{};
                     n = 0;
                     for (auto i = std::sregex_iterator{envString.begin(), envString.end(), storePathRegex}; i != env_end; ++i)
-                        unchecked.emplace((format("{%1%:%2%}") % envFile % envString).str(), i->str());
+                        unchecked.emplace((format("{memory:%1%:%2%}") % envFile % n++).str(), i->str());
                 } catch (SysError & e) {
                     if (errno == ENOENT || errno == EACCES || errno == ESRCH)
                         continue;
@@ -467,7 +467,7 @@ void LocalStore::findRuntimeRoots(Roots & roots)
         for (const auto & line : lsofLines) {
             std::smatch match;
             if (std::regex_match(line, match, lsofRegex))
-                unchecked.emplace((format("{%1%:%2%}" % LSOF % n++).str(), match[1]);
+                unchecked.emplace((format("{memory:%1%:%2%}" % LSOF % n++).str(), match[1]);
         }
     } catch (ExecError & e) {
         /* lsof not installed, lsof failed */
diff --git a/src/nix-daemon/nix-daemon.cc b/src/nix-daemon/nix-daemon.cc
index 8368c3266..faa23b268 100644
--- a/src/nix-daemon/nix-daemon.cc
+++ b/src/nix-daemon/nix-daemon.cc
@@ -478,8 +478,15 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         Roots roots = store->findRoots();
         logger->stopWork();
         to << roots.size();
-        for (auto & i : roots)
-            to << i.first << i.second;
+        int n = 0;
+        for (auto & i : roots) {
+            // Obfuscate 'memory' roots as they exposes information about other users,
+            if (i.first.rfind("{memory:", 0) == 0) {
+               to << fmt("{memory:%d}", n++) << i.second;
+            } else {
+               to << i.first << i.second;
+            }
+        }
         break;
     }