handle weak-security repositories as unauthenticated

APT can be forced to deal with repositories which have no security
features whatsoever, so just giving up on repositories which "just" fail
our current criteria of good security features is the wrong incentive.

Of course, repositories are better of fixing their setup to provide the
minimum of security features, but sometimes this isn't possible:
Historic repositories for example which do not change (anymore).

That also fixes problem with repositories which are marked as trusted,
but are providing only weak security features which would fail the
parsing of the Release file.

Closes: 827364

2 files changed, 59 insertions, 30 deletions

diff --git a/apt-pkg/acquire-item.cc b/apt-pkg/acquire-item.cc
index 699c30603..6f479ccef 100644
--- a/apt-pkg/acquire-item.cc
+++ b/apt-pkg/acquire-item.cc
@@ -1149,6 +1149,8 @@ bool pkgAcqMetaBase::CheckAuthDone(string const &Message)		/*{{{*/
    // valid signature from a key in the trusted keyring.  We
    // perform additional verification of its contents, and use them
    // to verify the indexes we are about to download
+   if (_config->FindB("Debug::pkgAcquire::Auth", false))
+      std::cerr << "Signature verification succeeded: " << DestFile << std::endl;
 
    if (TransactionManager->IMSHit == false)
    {
@@ -1169,7 +1171,9 @@ bool pkgAcqMetaBase::CheckAuthDone(string const &Message)		/*{{{*/
       LoadLastMetaIndexParser(TransactionManager, FinalRelease, FinalInRelease);
    }
 
-   if (TransactionManager->MetaIndexParser->Load(DestFile, &ErrorText) == false)
+   bool const GoodAuth = TransactionManager->MetaIndexParser->Load(DestFile, &ErrorText);
+   if (GoodAuth == false && AllowInsecureRepositories(_("The repository '%s' provides only weak security information."),
+							 Target.Description, TransactionManager->MetaIndexParser, TransactionManager, this) == false)
    {
       Status = StatAuthError;
       return false;
@@ -1181,14 +1185,10 @@ bool pkgAcqMetaBase::CheckAuthDone(string const &Message)		/*{{{*/
       return false;
    }
 
-   if (_config->FindB("Debug::pkgAcquire::Auth", false))
-      std::cerr << "Signature verification succeeded: "
-                << DestFile << std::endl;
-
    // Download further indexes with verification
-   TransactionManager->QueueIndexes(true);
+   TransactionManager->QueueIndexes(GoodAuth);
 
-   return true;
+   return GoodAuth;
 }
 									/*}}}*/
 void pkgAcqMetaClearSig::QueueIndexes(bool const verify)			/*{{{*/
@@ -1197,8 +1197,14 @@ void pkgAcqMetaClearSig::QueueIndexes(bool const verify)			/*{{{*/
    ExpectedAdditionalItems = 0;
 
    std::set<std::string> targetsSeen;
-   bool const metaBaseSupportsByHash = TransactionManager->MetaIndexParser->GetSupportsAcquireByHash();
-   for (auto &Target: TransactionManager->MetaIndexParser->GetIndexTargets())
+   bool const hasReleaseFile = TransactionManager->MetaIndexParser != NULL;
+   bool const metaBaseSupportsByHash = hasReleaseFile && TransactionManager->MetaIndexParser->GetSupportsAcquireByHash();
+   bool hasHashes = true;
+   auto IndexTargets = TransactionManager->MetaIndexParser->GetIndexTargets();
+   if (hasReleaseFile && verify == false)
+      hasHashes = std::any_of(IndexTargets.begin(), IndexTargets.end(),
+	    [&](IndexTarget const &Target) { return TransactionManager->MetaIndexParser->Exists(Target.MetaKey); });
+   for (auto&& Target: IndexTargets)
    {
       // if we have seen a target which is created-by a target this one here is declared a
       // fallback to, we skip acquiring the fallback (but we make sure we clean up)
@@ -1214,7 +1220,7 @@ void pkgAcqMetaClearSig::QueueIndexes(bool const verify)			/*{{{*/
       // download time, bandwidth and diskspace for nothing, BUT Debian doesn't feature all
       // in the set of supported architectures, so we can filter based on this property rather
       // than invent an entirely new flag we would need to carry for all of eternity.
-      if (Target.Option(IndexTarget::ARCHITECTURE) == "all")
+      if (hasReleaseFile && Target.Option(IndexTarget::ARCHITECTURE) == "all")
       {
 	 if (TransactionManager->MetaIndexParser->IsArchitectureSupported("all") == false ||
 	       TransactionManager->MetaIndexParser->IsArchitectureAllSupportedFor(Target) == false)
@@ -1225,12 +1231,12 @@ void pkgAcqMetaClearSig::QueueIndexes(bool const verify)			/*{{{*/
       }
 
       bool trypdiff = Target.OptionBool(IndexTarget::PDIFFS);
-      if (verify == true)
+      if (hasReleaseFile == true)
       {
 	 if (TransactionManager->MetaIndexParser->Exists(Target.MetaKey) == false)
 	 {
 	    // optional targets that we do not have in the Release file are skipped
-	    if (Target.IsOptional)
+	    if (hasHashes == true && Target.IsOptional)
 	    {
 	       new CleanupItem(Owner, TransactionManager, Target);
 	       continue;
@@ -1249,18 +1255,26 @@ void pkgAcqMetaClearSig::QueueIndexes(bool const verify)			/*{{{*/
 	       // if the architecture is officially supported but currently no packages for it available,
 	       // ignore silently as this is pretty much the same as just shipping an empty file.
 	       // if we don't know which architectures are supported, we do NOT ignore it to notify user about this
-	       if (TransactionManager->MetaIndexParser->IsArchitectureSupported("*undefined*") == false)
+	       if (hasHashes == true && TransactionManager->MetaIndexParser->IsArchitectureSupported("*undefined*") == false)
 	       {
 		  new CleanupItem(Owner, TransactionManager, Target);
 		  continue;
 	       }
 	    }
 
-	    Status = StatAuthError;
-	    strprintf(ErrorText, _("Unable to find expected entry '%s' in Release file (Wrong sources.list entry or malformed file)"), Target.MetaKey.c_str());
-	    return;
+	    if (hasHashes == true)
+	    {
+	       Status = StatAuthError;
+	       strprintf(ErrorText, _("Unable to find expected entry '%s' in Release file (Wrong sources.list entry or malformed file)"), Target.MetaKey.c_str());
+	       return;
+	    }
+	    else
+	    {
+	       new pkgAcqIndex(Owner, TransactionManager, Target);
+	       continue;
+	    }
 	 }
-	 else
+	 else if (verify)
 	 {
 	    auto const hashes = GetExpectedHashesFor(Target.MetaKey);
 	    if (hashes.empty() == false)
@@ -1530,6 +1544,17 @@ void pkgAcqMetaClearSig::Done(std::string const &Message,
 	 new NoActionItem(Owner, DetachedSigTarget);
       }
    }
+   else if (Status != StatAuthError)
+   {
+      string const FinalFile = GetFinalFileNameFromURI(DetachedDataTarget.URI);
+      string const OldFile = GetFinalFilename();
+      if (TransactionManager->IMSHit == false)
+	 TransactionManager->TransactionStageCopy(this, DestFile, FinalFile);
+      else if (RealFileExists(OldFile) == false)
+	 new NoActionItem(Owner, DetachedDataTarget);
+      else
+	 TransactionManager->TransactionStageCopy(this, OldFile, FinalFile);
+   }
 }
 									/*}}}*/
 void pkgAcqMetaClearSig::Failed(string const &Message,pkgAcquire::MethodConfig const * const Cnf) /*{{{*/
@@ -1735,6 +1760,14 @@ void pkgAcqMetaSig::Done(string const &Message, HashStringList const &Hashes,
 	 TransactionManager->TransactionStageCopy(MetaIndex, MetaIndex->DestFile, MetaIndex->GetFinalFilename());
       }
    }
+   else if (MetaIndex->Status != StatAuthError)
+   {
+      std::string const FinalFile = MetaIndex->GetFinalFilename();
+      if (TransactionManager->IMSHit == false)
+	 TransactionManager->TransactionStageCopy(MetaIndex, MetaIndex->DestFile, FinalFile);
+      else
+	 TransactionManager->TransactionStageCopy(MetaIndex, FinalFile, FinalFile);
+   }
 }
 									/*}}}*/
 void pkgAcqMetaSig::Failed(string const &Message,pkgAcquire::MethodConfig const * const Cnf)/*{{{*/
diff --git a/apt-pkg/deb/debmetaindex.cc b/apt-pkg/deb/debmetaindex.cc
index c70c39a45..0c9cde620 100644
--- a/apt-pkg/deb/debmetaindex.cc
+++ b/apt-pkg/deb/debmetaindex.cc
@@ -440,18 +440,13 @@ bool debReleaseIndex::Load(std::string const &Filename, std::string * const Erro
       }
    }
 
+   bool AuthPossible = false;
    if(FoundHashSum == false)
-   {
-      if (ErrorText != NULL)
-	 strprintf(*ErrorText, _("No Hash entry in Release file %s"), Filename.c_str());
-      return false;
-   }
-   if(FoundStrongHashSum == false)
-   {
-      if (ErrorText != NULL)
-	 strprintf(*ErrorText, _("No Hash entry in Release file %s which is considered strong enough for security purposes"), Filename.c_str());
-      return false;
-   }
+      _error->Warning(_("No Hash entry in Release file %s"), Filename.c_str());
+   else if(FoundStrongHashSum == false)
+      _error->Warning(_("No Hash entry in Release file %s which is considered strong enough for security purposes"), Filename.c_str());
+   else
+      AuthPossible = true;
 
    std::string const StrDate = Section.FindS("Date");
    if (RFC1123StrToTime(StrDate.c_str(), Date) == false)
@@ -539,8 +534,9 @@ bool debReleaseIndex::Load(std::string const &Filename, std::string * const Erro
       }
    }
 
-   LoadedSuccessfully = TRI_YES;
-   return true;
+   if (AuthPossible)
+      LoadedSuccessfully = TRI_YES;
+   return AuthPossible;
 }
 									/*}}}*/
 metaIndex * debReleaseIndex::UnloadedClone() const			/*{{{*/