From dceb1e49e4b8e4dadaf056be34088b415939cda6 Mon Sep 17 00:00:00 2001 From: Julian Andres Klode Date: Tue, 12 May 2020 11:49:09 +0200 Subject: SECURITY UPDATE: Fix out of bounds read in .ar and .tar implementation (CVE-2020-3810) When normalizing ar member names by removing trailing whitespace and slashes, an out-out-bound read can be caused if the ar member name consists only of such characters, because the code did not stop at 0, but would wrap around and continue reading from the stack, without any limit. Add a check to abort if we reached the first character in the name, effectively rejecting the use of names consisting just of slashes and spaces. Furthermore, certain error cases in arfile.cc and extracttar.cc have included member names in the output that were not checked at all and might hence not be nul terminated, leading to further out of bound reads. Fixes Debian/apt#111 LP: #1878177 --- apt-pkg/contrib/arfile.cc | 11 ++- apt-pkg/contrib/extracttar.cc | 2 +- test/integration/test-github-111-invalid-armember | 88 +++++++++++++++++++++++ 3 files changed, 98 insertions(+), 3 deletions(-) create mode 100755 test/integration/test-github-111-invalid-armember diff --git a/apt-pkg/contrib/arfile.cc b/apt-pkg/contrib/arfile.cc index 3fc3afedb..5cb43c690 100644 --- a/apt-pkg/contrib/arfile.cc +++ b/apt-pkg/contrib/arfile.cc @@ -92,7 +92,7 @@ bool ARArchive::LoadHeaders() StrToNum(Head.Size,Memb->Size,sizeof(Head.Size)) == false) { delete Memb; - return _error->Error(_("Invalid archive member header %s"), Head.Name); + return _error->Error(_("Invalid archive member header")); } // Check for an extra long name string @@ -119,7 +119,14 @@ bool ARArchive::LoadHeaders() else { unsigned int I = sizeof(Head.Name) - 1; - for (; Head.Name[I] == ' ' || Head.Name[I] == '/'; I--); + for (; Head.Name[I] == ' ' || Head.Name[I] == '/'; I--) + { + if (I == 0) + { + delete Memb; + return _error->Error(_("Invalid archive member header")); + } + } Memb->Name = std::string(Head.Name,I+1); } diff --git a/apt-pkg/contrib/extracttar.cc b/apt-pkg/contrib/extracttar.cc index 9bb0a55c0..b22f59dbc 100644 --- a/apt-pkg/contrib/extracttar.cc +++ b/apt-pkg/contrib/extracttar.cc @@ -254,7 +254,7 @@ bool ExtractTar::Go(pkgDirStream &Stream) default: BadRecord = true; - _error->Warning(_("Unknown TAR header type %u, member %s"),(unsigned)Tar->LinkFlag,Tar->Name); + _error->Warning(_("Unknown TAR header type %u"), (unsigned)Tar->LinkFlag); break; } diff --git a/test/integration/test-github-111-invalid-armember b/test/integration/test-github-111-invalid-armember new file mode 100755 index 000000000..ec2163bf6 --- /dev/null +++ b/test/integration/test-github-111-invalid-armember @@ -0,0 +1,88 @@ +#!/bin/sh +set -e + +TESTDIR="$(readlink -f "$(dirname "$0")")" +. "$TESTDIR/framework" +setupenvironment +configarchitecture "amd64" +setupaptarchive + +# this used to crash, but it should treat it as an invalid member header +touch ' ' +ar -q test.deb ' ' +testsuccessequal "E: Invalid archive member header" ${BUILDDIRECTORY}/../test/interactive-helper/testdeb test.deb + + +rm test.deb +touch 'x' +ar -q test.deb 'x' +testsuccessequal "E: This is not a valid DEB archive, missing 'debian-binary' member" ${BUILDDIRECTORY}/../test/interactive-helper/testdeb test.deb + + +# [ other fields] - name is not nul terminated here, it ends in . +msgmsg "Unterminated ar member name" +printf '!\0120123456789ABCDE.A123456789A.01234.01234.0123456.012345678.0.' > test.deb +testsuccessequal "E: Invalid archive member header" ${BUILDDIRECTORY}/../test/interactive-helper/testdeb test.deb + + +# unused source code for generating $tar below +maketar() { + cat > maketar.c << EOF + #include + #include + struct tar { + char Name[100]; + char Mode[8]; + char UserID[8]; + char GroupID[8]; + char Size[12]; + char MTime[12]; + char Checksum[8]; + char LinkFlag; + char LinkName[100]; + char MagicNumber[8]; + char UserName[32]; + char GroupName[32]; + char Major[8]; + char Minor[8]; + }; + + int main(void) + { + union { + struct tar t; + char buf[512]; + } t; + for (int i = 0; i < sizeof(t.buf); i++) + t.buf[i] = '7'; + memcpy(t.t.Name, "unterminatedName", 16); + memcpy(t.t.UserName, "userName", 8); + memcpy(t.t.GroupName, "thisIsAGroupNamethisIsAGroupName", 32); + t.t.LinkFlag = 'X'; // I AM BROKEN + memcpy(t.t.Size, "000000000000", sizeof(t.t.Size)); + memset(t.t.Checksum,' ',sizeof(t.t.Checksum)); + + unsigned long sum = 0; + for (int i = 0; i < sizeof(t.buf); i++) + sum += t.buf[i]; + + int written = sprintf(t.t.Checksum, "%lo", sum); + for (int i = written; i < sizeof(t.t.Checksum); i++) + t.t.Checksum[i] = ' '; + fwrite(t.buf, sizeof(t.buf), 1, stdout); + } +EOF + + gcc maketar.c -o maketar -Wall + ./maketar +} + + +# +tar="unterminatedName77777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777700000000000077777777777773544 X777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777userName777777777777777777777777thisIsAGroupNamethisIsAGroupName777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777" +printf '%s' "$tar" | gzip > control.tar.gz +cp control.tar.gz data.tar.gz +touch debian-binary +rm test.deb +ar -q test.deb debian-binary control.tar.gz data.tar.gz +testsuccessequal "W: Unknown TAR header type 88" ${BUILDDIRECTORY}/../test/interactive-helper/testdeb test.deb -- cgit v1.2.3-70-g09d2