Check that Date of Release file is not in the future

By restricting the Date field to be in the past, an attacker cannot
just create a repository from the future that would be accepted as
a valid update for a repository.

This check can be disabled by Acquire::Check-Date set to false. This
will also disable Check-Valid-Until and any future date related checking,
if any - the option means: "my computers date cannot be trusted."

Modify the tests to allow repositories to be up to 10 hours in the
future, so we can keep using hours there to simulate time changes.

2 files changed, 97 insertions, 43 deletions

diff --git a/apt-pkg/deb/debmetaindex.cc b/apt-pkg/deb/debmetaindex.cc
index 59a26390e..6cbed85a7 100644
--- a/apt-pkg/deb/debmetaindex.cc
+++ b/apt-pkg/deb/debmetaindex.cc
@@ -49,12 +49,16 @@ class APT_HIDDEN debReleaseIndexPrivate					/*{{{*/
    time_t ValidUntilMin;
    time_t ValidUntilMax;
 
+   metaIndex::TriState CheckDate;
+   time_t DateMaxFuture;
+   time_t NotBefore;
+
    std::vector<std::string> Architectures;
    std::vector<std::string> NoSupportForAll;
    std::vector<std::string> SupportedComponents;
    std::map<std::string, std::string> const ReleaseOptions;
 
-   debReleaseIndexPrivate(std::map<std::string, std::string> const &Options) : CheckValidUntil(metaIndex::TRI_UNSET), ValidUntilMin(0), ValidUntilMax(0), ReleaseOptions(Options) {}
+   debReleaseIndexPrivate(std::map<std::string, std::string> const &Options) : CheckValidUntil(metaIndex::TRI_UNSET), ValidUntilMin(0), ValidUntilMax(0), CheckDate(metaIndex::TRI_UNSET), DateMaxFuture(0), NotBefore(0), ReleaseOptions(Options) {}
 };
 									/*}}}*/
 // ReleaseIndex::MetaIndex* - display helpers				/*{{{*/
@@ -482,54 +486,77 @@ bool debReleaseIndex::Load(std::string const &Filename, std::string * const Erro
       Date = 0;
    }
 
-   bool CheckValidUntil = _config->FindB("Acquire::Check-Valid-Until", true);
-   if (d->CheckValidUntil == metaIndex::TRI_NO)
-      CheckValidUntil = false;
-   else if (d->CheckValidUntil == metaIndex::TRI_YES)
-      CheckValidUntil = true;
+   bool CheckDate = _config->FindB("Acquire::Check-Date", true);
+   if (d->CheckDate == metaIndex::TRI_NO)
+      CheckDate = false;
+   else if (d->CheckDate == metaIndex::TRI_YES)
+      CheckDate = true;
 
-   if (CheckValidUntil == true)
+   if (CheckDate)
    {
-      std::string const StrValidUntil = Section.FindS("Valid-Until");
-
-      // if we have a Valid-Until header in the Release file, use it as default
-      if (StrValidUntil.empty() == false)
-      {
-	 if(RFC1123StrToTime(StrValidUntil.c_str(), ValidUntil) == false)
-	 {
-	    if (ErrorText != NULL)
-	       strprintf(*ErrorText, _("Invalid '%s' entry in Release file %s"), "Valid-Until", Filename.c_str());
-	    return false;
-	 }
-      }
       auto const Label = GetLabel();
-      // get the user settings for this archive and use what expires earlier
-      time_t MaxAge = d->ValidUntilMax;
-      if (MaxAge == 0)
-      {
-	 MaxAge = _config->FindI("Acquire::Max-ValidTime", 0);
-	 if (Label.empty() == false)
-	    MaxAge = _config->FindI(("Acquire::Max-ValidTime::" + Label).c_str(), MaxAge);
-      }
-      time_t MinAge = d->ValidUntilMin;
-      if (MinAge == 0)
+      // get the user settings for this archive
+      time_t MaxFuture = d->DateMaxFuture;
+      if (MaxFuture == 0)
       {
-	 MinAge = _config->FindI("Acquire::Min-ValidTime", 0);
+	 MaxFuture = _config->FindI("Acquire::Max-FutureTime", 10);
 	 if (Label.empty() == false)
-	    MinAge = _config->FindI(("Acquire::Min-ValidTime::" + Label).c_str(), MinAge);
+	    MaxFuture = _config->FindI(("Acquire::Max-FutureTime::" + Label).c_str(), MaxFuture);
       }
 
-      if (MinAge != 0 || ValidUntil != 0 || MaxAge != 0)
+      d->NotBefore = Date - MaxFuture;
+
+      bool CheckValidUntil = _config->FindB("Acquire::Check-Valid-Until", true);
+      if (d->CheckValidUntil == metaIndex::TRI_NO)
+	 CheckValidUntil = false;
+      else if (d->CheckValidUntil == metaIndex::TRI_YES)
+	 CheckValidUntil = true;
+
+      if (CheckValidUntil == true)
       {
-	 if (MinAge != 0 && ValidUntil != 0) {
-	    time_t const min_date = Date + MinAge;
-	    if (ValidUntil < min_date)
-	       ValidUntil = min_date;
+	 std::string const StrValidUntil = Section.FindS("Valid-Until");
+
+	 // if we have a Valid-Until header in the Release file, use it as default
+	 if (StrValidUntil.empty() == false)
+	 {
+	    if (RFC1123StrToTime(StrValidUntil.c_str(), ValidUntil) == false)
+	    {
+	       if (ErrorText != NULL)
+		  strprintf(*ErrorText, _("Invalid '%s' entry in Release file %s"), "Valid-Until", Filename.c_str());
+	       return false;
+	    }
+	 }
+	 auto const Label = GetLabel();
+	 // get the user settings for this archive and use what expires earlier
+	 time_t MaxAge = d->ValidUntilMax;
+	 if (MaxAge == 0)
+	 {
+	    MaxAge = _config->FindI("Acquire::Max-ValidTime", 0);
+	    if (Label.empty() == false)
+	       MaxAge = _config->FindI(("Acquire::Max-ValidTime::" + Label).c_str(), MaxAge);
+	 }
+	 time_t MinAge = d->ValidUntilMin;
+	 if (MinAge == 0)
+	 {
+	    MinAge = _config->FindI("Acquire::Min-ValidTime", 0);
+	    if (Label.empty() == false)
+	       MinAge = _config->FindI(("Acquire::Min-ValidTime::" + Label).c_str(), MinAge);
 	 }
-	 if (MaxAge != 0 && Date != 0) {
-	    time_t const max_date = Date + MaxAge;
-	    if (ValidUntil == 0 || ValidUntil > max_date)
-	       ValidUntil = max_date;
+
+	 if (MinAge != 0 || ValidUntil != 0 || MaxAge != 0)
+	 {
+	    if (MinAge != 0 && ValidUntil != 0)
+	    {
+	       time_t const min_date = Date + MinAge;
+	       if (ValidUntil < min_date)
+		  ValidUntil = min_date;
+	    }
+	    if (MaxAge != 0 && Date != 0)
+	    {
+	       time_t const max_date = Date + MaxAge;
+	       if (ValidUntil == 0 || ValidUntil > max_date)
+		  ValidUntil = max_date;
+	    }
 	 }
       }
    }
@@ -566,6 +593,11 @@ bool debReleaseIndex::Load(std::string const &Filename, std::string * const Erro
    return AuthPossible;
 }
 									/*}}}*/
+time_t debReleaseIndex::GetNotBefore() const /*{{{*/
+{
+   return d->NotBefore;
+}
+									/*}}}*/
 metaIndex * debReleaseIndex::UnloadedClone() const			/*{{{*/
 {
    if (Trusted == TRI_NO)
@@ -685,6 +717,22 @@ bool debReleaseIndex::SetValidUntilMax(time_t const Valid)
       return _error->Error(_("Conflicting values set for option %s regarding source %s %s"), "Max-ValidTime", URI.c_str(), Dist.c_str());
    return true;
 }
+bool debReleaseIndex::SetCheckDate(TriState const pCheckDate)
+{
+   if (d->CheckDate == TRI_UNSET)
+      d->CheckDate = pCheckDate;
+   else if (d->CheckDate != pCheckDate)
+      return _error->Error(_("Conflicting values set for option %s regarding source %s %s"), "Check-Date", URI.c_str(), Dist.c_str());
+   return true;
+}
+bool debReleaseIndex::SetDateMaxFuture(time_t const DateMaxFuture)
+{
+   if (d->DateMaxFuture == 0)
+      d->DateMaxFuture = DateMaxFuture;
+   else if (d->DateMaxFuture != DateMaxFuture)
+      return _error->Error(_("Conflicting values set for option %s regarding source %s %s"), "Date-Max-Future", URI.c_str(), Dist.c_str());
+   return true;
+}
 bool debReleaseIndex::SetSignedBy(std::string const &pSignedBy)
 {
    if (SignedBy.empty() == true && pSignedBy.empty() == false)
@@ -1168,9 +1216,11 @@ class APT_HIDDEN debSLTypeDebian : public pkgSourceList::Type		/*{{{*/
 	    );
 
       if (Deb->SetTrusted(GetTriStateOption(Options, "trusted")) == false ||
-	 Deb->SetCheckValidUntil(GetTriStateOption(Options, "check-valid-until")) == false ||
-	 Deb->SetValidUntilMax(GetTimeOption(Options, "valid-until-max")) == false ||
-	 Deb->SetValidUntilMin(GetTimeOption(Options, "valid-until-min")) == false)
+	  Deb->SetCheckValidUntil(GetTriStateOption(Options, "check-valid-until")) == false ||
+	  Deb->SetValidUntilMax(GetTimeOption(Options, "valid-until-max")) == false ||
+	  Deb->SetValidUntilMin(GetTimeOption(Options, "valid-until-min")) == false ||
+	  Deb->SetCheckDate(GetTriStateOption(Options, "check-date")) == false ||
+	  Deb->SetDateMaxFuture(GetTimeOption(Options, "date-max-future")) == false)
 	 return false;
 
       std::map<std::string, std::string>::const_iterator const signedby = Options.find("signed-by");
diff --git a/apt-pkg/deb/debmetaindex.h b/apt-pkg/deb/debmetaindex.h
index 5a97cfc78..864ac3eba 100644
--- a/apt-pkg/deb/debmetaindex.h
+++ b/apt-pkg/deb/debmetaindex.h
@@ -55,6 +55,8 @@ class APT_HIDDEN debReleaseIndex : public metaIndex
    bool SetCheckValidUntil(TriState const Trusted);
    bool SetValidUntilMin(time_t const Valid);
    bool SetValidUntilMax(time_t const Valid);
+   bool SetCheckDate(TriState const CheckDate);
+   bool SetDateMaxFuture(time_t const DateMaxFuture);
    bool SetSignedBy(std::string const &SignedBy);
    std::map<std::string, std::string> GetReleaseOptions();
 
@@ -63,6 +65,8 @@ class APT_HIDDEN debReleaseIndex : public metaIndex
    bool IsArchitectureAllSupportedFor(IndexTarget const &target) const;
    bool HasSupportForComponent(std::string const &component) const;
 
+   APT_PURE time_t GetNotBefore() const;
+
    void AddComponent(std::string const &sourcesEntry,
 	 bool const isSrc, std::string const &Name,
 	 std::vector<std::string> const &Targets,