Implement gpgv --assert-pubkey-algo=>=rsa2048,ed25519,ed448

The assertion can be overriden using apt::key::assert-pubkey-algo,
the default is the most opinionated one.

This will inform the user during apt-cdrom add as we do not
pass --quiet to user, so adjust test case.

Add a simple test case for it to test-method-gpgv.

LP: #2055193

6 files changed, 75 insertions, 5 deletions

diff --git a/apt-pkg/init.cc b/apt-pkg/init.cc
index f1742c019..75935404f 100644
--- a/apt-pkg/init.cc
+++ b/apt-pkg/init.cc
@@ -131,6 +131,7 @@ bool pkgInitConfig(Configuration &Cnf)
       Cnf.Set("APT::Build-Essential::", "build-essential");
    Cnf.CndSet("APT::Install-Recommends", true);
    Cnf.CndSet("APT::Install-Suggests", false);
+   Cnf.CndSet("APT::Key::Assert-Pubkey-Algo", ">=rsa2048,ed25519,ed448");
    Cnf.CndSet("Dir","/");
    
    // State
diff --git a/cmdline/apt-key.in b/cmdline/apt-key.in
index 4f3e9c8e1..07522723b 100644
--- a/cmdline/apt-key.in
+++ b/cmdline/apt-key.in
@@ -800,7 +800,8 @@ case "$command" in
 	;;
     verify)
 	GPGV=''
-	eval $(apt-config shell GPGV Apt::Key::gpgvcommand)
+	ASSERT_PUBKEY_ALGO=''
+	eval $(apt-config shell GPGV Apt::Key::gpgvcommand ASSERT_PUBKEY_ALGO Apt::Key::assert-pubkey-algo)
 	if [ -n "$GPGV" ] && command_available "$GPGV"; then true;
 	elif command_available 'gpgv'; then GPGV='gpgv';
 	elif command_available 'gpgv2'; then GPGV='gpgv2';
@@ -809,6 +810,20 @@ case "$command" in
 	   apt_error 'gpgv, gpgv2 or gpgv1 required for verification, but neither seems installed'
 	   exit 29
 	fi
+	GPGV_ARGS=""
+	if [ "$ASSERT_PUBKEY_ALGO" ]; then
+		test="$(LC_ALL=C.UTF-8 "$GPGV" --assert-pubkey-algo 2>&1 || :)"
+		case "$test" in
+			*"missing argument"*)
+				GPGV_ARGS="--assert-pubkey-algo=$ASSERT_PUBKEY_ALGO"
+				;;
+			*[Ii]"nvalid option"*"assert-pubkey-algo"*)
+				;;
+			*)
+				apt_warn "Unknown response from gpgv to --assert-pubkey-algo check: $test"
+				;;
+		esac
+	fi
 	# for a forced keyid we need gpg --export, so full wrapping required
 	if [ -n "$FORCED_KEYID" ]; then
 	    prepare_gpg_home
@@ -817,9 +832,9 @@ case "$command" in
 	fi
 	setup_merged_keyring
 	if [ -n "$FORCED_KEYRING" ]; then
-	    "$GPGV" --homedir "${GPGHOMEDIR}" --keyring "$(dearmor_filename "${FORCED_KEYRING}")" --ignore-time-conflict "$@"
+	    "$GPGV" $GPGV_ARGS --homedir "${GPGHOMEDIR}" --keyring "$(dearmor_filename "${FORCED_KEYRING}")" --ignore-time-conflict "$@"
 	else
-	    "$GPGV" --homedir "${GPGHOMEDIR}" --keyring "${GPGHOMEDIR}/pubring.gpg" --ignore-time-conflict "$@"
+	    "$GPGV" $GPGV_ARGS --homedir "${GPGHOMEDIR}" --keyring "${GPGHOMEDIR}/pubring.gpg" --ignore-time-conflict "$@"
 	fi
 	;;
     help)
diff --git a/doc/examples/configure-index b/doc/examples/configure-index
index f37b7696c..da4998b4d 100644
--- a/doc/examples/configure-index
+++ b/doc/examples/configure-index
@@ -762,6 +762,7 @@ apt::key::gpgcommand "<STRING>";
 apt::key::masterkeyring "<STRING>";
 apt::key::archivekeyringuri "<STRING>";
 apt::key::net-update-enabled "<STRING>";
+apt::key::assert-pubkey-algo "<STRING>";
 
 apt::ftparchive::release::patterns "<LIST>";
 apt::ftparchive::release::validtime "<INT>";
diff --git a/methods/gpgv.cc b/methods/gpgv.cc
index b2e73c9fe..8b365b6d4 100644
--- a/methods/gpgv.cc
+++ b/methods/gpgv.cc
@@ -42,6 +42,7 @@ using std::vector;
 #define GNUPGNODATA "[GNUPG:] NODATA"
 #define GNUPGWARNING "[GNUPG:] WARNING"
 #define GNUPGERROR "[GNUPG:] ERROR"
+#define GNUPGASSERT_PUBKEY_ALGO "[GNUPG:] ASSERT_PUBKEY_ALGO"
 #define APTKEYWARNING "[APTKEY:] WARNING"
 #define APTKEYERROR "[APTKEY:] ERROR"
 
@@ -242,6 +243,25 @@ string GPGVMethod::VerifyGetSigners(const char *file, const char *outfile,
 	 PushEntryWithUID(Signers.Worthless, buffer, Debug);
       else if (strncmp(buffer, GNUPGREVKEYSIG, sizeof(GNUPGREVKEYSIG)-1) == 0)
 	 PushEntryWithUID(Signers.Worthless, buffer, Debug);
+      else if (strncmp(buffer, GNUPGASSERT_PUBKEY_ALGO, sizeof(GNUPGASSERT_PUBKEY_ALGO) - 1) == 0)
+      {
+	 std::istringstream iss(buffer + sizeof(GNUPGASSERT_PUBKEY_ALGO));
+	 vector<string> tokens{std::istream_iterator<string>{iss},
+			       std::istream_iterator<string>{}};
+
+	 auto const fpr = tokens[0];
+	 auto const asserted = atoi(tokens[1].c_str());
+	 auto const pkstr = tokens[2];
+	 if (not asserted)
+	 {
+	    std::string reason;
+	    strprintf(reason, _("untrusted public key algorithm: %s"), pkstr.c_str());
+	    Signers.Worthless.push_back({fpr, reason});
+	    Signers.Good.erase(std::remove_if(Signers.Good.begin(), Signers.Good.end(), [&](std::string const &goodsig)
+					      { return IsTheSameKey(fpr, goodsig); }),
+			       Signers.Good.end());
+	 }
+      }
       else if (strncmp(buffer, GNUPGGOODSIG, sizeof(GNUPGGOODSIG)-1) == 0)
 	 PushEntryWithKeyID(Signers.Good, buffer, Debug);
       else if (strncmp(buffer, GNUPGVALIDSIG, sizeof(GNUPGVALIDSIG)-1) == 0)
diff --git a/test/integration/test-apt-cdrom b/test/integration/test-apt-cdrom
index 01680c461..e8ccb10a4 100755
--- a/test/integration/test-apt-cdrom
+++ b/test/integration/test-apt-cdrom
@@ -40,6 +40,24 @@ aptcdromlog() {
 }
 aptautotest_aptcdromlog_add() { aptautotest_aptget_update "$@"; }
 
+
+msgtest "Checking --assert-pubkey-algo support"
+gpgv_msg=""
+test="$(LC_ALL=C.UTF-8 gpgv --assert-pubkey-algo 2>&1 || :)"
+case "$test" in
+	*"missing argument"*)
+		gpgv_msg="
+gpgv: asserted signer '34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE' with algo rsa2048"
+		msgpass
+		;;
+	*[Ii]"nvalid option"*"assert-pubkey-algo"*)
+		msgskip
+		;;
+	*)
+		msgfail "Unknown response from gpgv to --assert-pubkey-algo check: $test"
+		;;
+esac
+
 CDROM_PRE="Using CD-ROM mount point $(readlink -f ./rootdir/media)/cdrom/
 Unmounting CD-ROM...
 Waiting for disc...
@@ -47,7 +65,7 @@ Please insert a Disc in the drive and press [Enter]
 Mounting CD-ROM...
 Scanning disc for index files..."
 CDROM_POST="This disc is called: 
-'Debian APT Testdisk 0.8.15'
+'Debian APT Testdisk 0.8.15'$gpgv_msg
 Writing new source list
 Source list entries for this disc are:
 deb cdrom:[Debian APT Testdisk 0.8.15]/ stable main
diff --git a/test/integration/test-method-gpgv b/test/integration/test-method-gpgv
index 99bffd6ab..4fd72d256 100755
--- a/test/integration/test-method-gpgv
+++ b/test/integration/test-method-gpgv
@@ -41,6 +41,13 @@ testrun() {
 	testgpgv 'Good signed with fingerprint' 'Good: GOODSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE' '34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE!' '[GNUPG:] GOODSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
 [GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 11 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE'
 
+	testgpgv 'Good signed with long keyid and asserted' 'Good: GOODSIG 5A90D141DBAC8DAE' '34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE!' '[GNUPG:] GOODSIG 5A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
+[GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 11 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE
+[GNUPG:] ASSERT_PUBKEY_ALGO 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 1 rsa1024'
+	testgpgv 'Good signed with fingerprint and asserted' 'Good: GOODSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE' '34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE!' '[GNUPG:] GOODSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
+[GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 11 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE
+[GNUPG:] ASSERT_PUBKEY_ALGO 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 1 rsa1024'
+
 	testgpgv 'Good subkey signed with long keyid' 'Good: GOODSIG 5B6896415D44C43E' '34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE, 4281DEDBD466EAE8C1F4157E5B6896415D44C43E!' '[GNUPG:] GOODSIG 5B6896415D44C43E Sebastian Subkey <subkey@example.org>
 [GNUPG:] VALIDSIG 4281DEDBD466EAE8C1F4157E5B6896415D44C43E 2018-08-16 1534459673 0 4 0 1 11 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE'
 	testgpgv 'Good subkey signed with fingerprint' 'Good: GOODSIG 4281DEDBD466EAE8C1F4157E5B6896415D44C43E' '34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE, 4281DEDBD466EAE8C1F4157E5B6896415D44C43E!' '[GNUPG:] GOODSIG 4281DEDBD466EAE8C1F4157E5B6896415D44C43E Sebastian Subkey <subkey@example.org>
@@ -48,12 +55,20 @@ testrun() {
 
 	testgpgv 'Untrusted signed with long keyid' 'Worthless: 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE, ' '' '[GNUPG:] GOODSIG 5A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
 [GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 1 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE'
-    exit
 	testsuccess grep '^\s\+Good:\s\+$' method.output
 	testgpgv 'Untrusted signed with fingerprint' 'Worthless: 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE, ' '' '[GNUPG:] GOODSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
 [GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 1 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE'
 	testsuccess grep '^\s\+Good:\s\+$' method.output
 
+	testgpgv 'Unasserted signed with long keyid' 'Worthless: 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE, ' '' '[GNUPG:] GOODSIG 5A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
+[GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 11 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE
+[GNUPG:] ASSERT_PUBKEY_ALGO 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 0 rsa1024'
+	testsuccess grep '^\s\+Good:\s\+$' method.output
+	testgpgv 'Unaserted signed with fingerprint' 'Worthless: 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE, ' '' '[GNUPG:] GOODSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
+[GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 11 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE
+[GNUPG:] ASSERT_PUBKEY_ALGO 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 0 rsa1024'
+	testsuccess grep '^\s\+Good:\s\+$' method.output
+
 	testgpgv 'Weak signed with long keyid' 'Good: GOODSIG 5A90D141DBAC8DAE' '34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE!' '[GNUPG:] GOODSIG 5A90D141DBAC8DAE Joe Sixpack (APT Testcases Dummy) <joe@example.org>
 [GNUPG:] VALIDSIG 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE 2016-09-01 1472742625 0 4 0 1 2 00 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE'
 	testsuccess grep '^Message: Signature by key 34A8E9D18DB320F367E8EAA05A90D141DBAC8DAE uses weak digest algorithm (SHA1)$' method.output