Based on upstream changeset:
  https://hg.mozilla.org/releases/mozilla-esr60/rev/300efdbc9fe1
but with the git binary patch and related test changes omitted,
and adapted to apply cleanly to GNU IceCat.

# HG changeset patch
# User David Keeler <dkeeler@mozilla.com>
# Date 1531860660 25200
# Node ID 300efdbc9fe1f9165428c7934861033935b5abfa
# Parent  80a4a7ef281374dbb2afda8edac54665b14b9ef8
Bug 1475775 - Clean up old NSS DB file after upgrade if necessary. r=franziskus, r=mattn, a=RyanVM

Reviewers: franziskus, mattn

Bug #: 1475775

Differential Revision: https://phabricator.services.mozilla.com/D2202

diff --git a/security/manager/ssl/nsNSSComponent.cpp b/security/manager/ssl/nsNSSComponent.cpp
--- a/security/manager/ssl/nsNSSComponent.cpp
+++ b/security/manager/ssl/nsNSSComponent.cpp
@@ -1935,16 +1935,61 @@ AttemptToRenameBothPKCS11ModuleDBVersion
   NS_NAMED_LITERAL_CSTRING(sqlModuleDBFilename, "pkcs11.txt");
   nsresult rv = AttemptToRenamePKCS11ModuleDB(profilePath,
                                               legacyModuleDBFilename);
   if (NS_FAILED(rv)) {
     return rv;
   }
   return AttemptToRenamePKCS11ModuleDB(profilePath, sqlModuleDBFilename);
 }
+
+// When we changed from the old dbm database format to the newer sqlite
+// implementation, the upgrade process left behind the existing files. Suppose a
+// user had not set a password for the old key3.db (which is about 99% of
+// users). After upgrading, both the old database and the new database are
+// unprotected. If the user then sets a password for the new database, the old
+// one will not be protected. In this scenario, we should probably just remove
+// the old database (it would only be relevant if the user downgraded to a
+// version of IceCat before 58, but we have to trade this off against the
+// user's old private keys being unexpectedly unprotected after setting a
+// password).
+// This was never an issue on Android because we always used the new
+// implementation.
+static void
+MaybeCleanUpOldNSSFiles(const nsACString& profilePath)
+{
+  UniquePK11SlotInfo slot(PK11_GetInternalKeySlot());
+  if (!slot) {
+    return;
+  }
+  // Unfortunately we can't now tell the difference between "there already was a
+  // password when the upgrade happened" and "there was not a password but then
+  // the user added one after upgrading".
+  bool hasPassword = PK11_NeedLogin(slot.get()) &&
+                     !PK11_NeedUserInit(slot.get());
+  if (!hasPassword) {
+    return;
+  }
+  nsCOMPtr<nsIFile> dbFile = do_CreateInstance("@mozilla.org/file/local;1");
+  if (!dbFile) {
+    return;
+  }
+  nsresult rv = dbFile->InitWithNativePath(profilePath);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+  NS_NAMED_LITERAL_CSTRING(keyDBFilename, "key3.db");
+  rv = dbFile->AppendNative(keyDBFilename);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+  // Since this isn't a directory, the `recursive` argument to `Remove` is
+  // irrelevant.
+  Unused << dbFile->Remove(false);
+}
 #endif // ifndef ANDROID
 
 // Given a profile directory, attempt to initialize NSS. If nocertdb is true,
 // (or if we don't have a profile directory) simply initialize NSS in no DB mode
 // and return. Otherwise, first attempt to initialize in read/write mode, and
 // then read-only mode if that fails. If both attempts fail, we may be failing
 // to initialize an NSS DB collection that has FIPS mode enabled. Attempt to
 // ascertain if this is the case, and if so, rename the offending PKCS#11 module
@@ -1966,16 +2011,19 @@ InitializeNSSWithFallbacks(const nsACStr
 
   // Try read/write mode. If we're in safeMode, we won't load PKCS#11 modules.
 #ifndef ANDROID
   PRErrorCode savedPRErrorCode1;
 #endif // ifndef ANDROID
   SECStatus srv = ::mozilla::psm::InitializeNSS(profilePath, false, !safeMode);
   if (srv == SECSuccess) {
     MOZ_LOG(gPIPNSSLog, LogLevel::Debug, ("initialized NSS in r/w mode"));
+#ifndef ANDROID
+    MaybeCleanUpOldNSSFiles(profilePath);
+#endif // ifndef ANDROID
     return NS_OK;
   }
 #ifndef ANDROID
   savedPRErrorCode1 = PR_GetError();
   PRErrorCode savedPRErrorCode2;
 #endif // ifndef ANDROID
   // That failed. Try read-only mode.
   srv = ::mozilla::psm::InitializeNSS(profilePath, true, !safeMode);