Merge branch '2.6' into 2.7

3 files changed, 48 insertions, 1 deletions

diff --git a/paramiko/kex_group1.py b/paramiko/kex_group1.py
index 5131e895..dce3fd91 100644
--- a/paramiko/kex_group1.py
+++ b/paramiko/kex_group1.py
@@ -140,7 +140,7 @@ class KexGroup1(object):
         hm.add_mpint(self.e)
         hm.add_mpint(self.f)
         hm.add_mpint(K)
-        H = sha1(hm.asbytes()).digest()
+        H = self.hash_algo(hm.asbytes()).digest()
         self.transport._set_K_H(K, H)
         # sign it
         sig = self.transport.get_server_key().sign_ssh_data(H)
diff --git a/sites/www/changelog.rst b/sites/www/changelog.rst
index f3ff0749..3582b775 100644
--- a/sites/www/changelog.rst
+++ b/sites/www/changelog.rst
@@ -2,6 +2,11 @@
 Changelog
 =========
 
+- :bug:`1882` Newer server-side key exchange algorithms not intended to use
+  SHA1 (``diffie-hellman-group14-sha256``, ``diffie-hellman-group16-sha512``)
+  were incorrectly using SHA1 after all, due to a bug causing them to ignore
+  the ``hash_algo`` class attribute. This has been corrected. Big thanks to
+  Benno Rice for catch & patch.
 - :release:`2.7.2 <2020-08-30>`
 - :support:`- backported` Update our CI to catch issues with sdist generation,
   installation and testing.
diff --git a/tests/test_kex.py b/tests/test_kex.py
index 0244ae84..246e0020 100644
--- a/tests/test_kex.py
+++ b/tests/test_kex.py
@@ -548,6 +548,27 @@ class KexTest(unittest.TestCase):
         self.assertEqual((b"fake-host-key", b"fake-sig"), transport._verify)
         self.assertTrue(transport._activated)
 
+    def test_kex_group14_sha256_server(self):
+        transport = FakeTransport()
+        transport.server_mode = True
+        kex = KexGroup14SHA256(transport)
+        kex.start_kex()
+        self.assertEqual(
+            (paramiko.kex_group1._MSG_KEXDH_INIT,), transport._expect
+        )
+
+        msg = Message()
+        msg.add_mpint(69)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_group1._MSG_KEXDH_INIT, msg)
+        K = 21526936926159575624241589599003964979640840086252478029709904308461709651400109485351462666820496096345766733042945918306284902585618061272525323382142547359684512114160415969631877620660064043178086464811345023251493620331559440565662862858765724251890489795332144543057725932216208403143759943169004775947331771556537814494448612329251887435553890674764339328444948425882382475260315505741818518926349729970262019325118040559191290279100613049085709127598666890434114956464502529053036826173452792849566280474995114751780998069614898221773345705289637708545219204637224261997310181473787577166103031529148842107599  # noqa
+        H = b"15080A19894D489ACD0DA724480E1B08E71293E07EBC25FAD10F263C00B343DC"
+        x = b"1F0000000866616B652D6B657900000101009850B3A8DE3ECCD3F19644139137C93D9C11BC28ED8BE850908EE294E1D43B88B9295311EFAEF5B736A1B652EBE184CCF36CFB0681C1ED66430088FA448B83619F928E7B9592ED6160EC11D639D51C303603F930F743C646B1B67DA38A1D44598DCE6C3F3019422B898044141420E9A10C29B9C58668F7F20A40F154B2C4768FCF7A9AA7179FB6366A7167EE26DD58963E8B880A0572F641DE0A73DC74C930F7C3A0C9388553F3F8403E40CF8B95FEDB1D366596FCF3FDDEB21A0005ADA650EF1733628D807BE5ACB83925462765D9076570056E39994FB328E3108FE406275758D6BF5F32790EF15D8416BF5548164859E785DB45E7787BB0E727ADE08641ED0000000866616B652D736967"  # noqa
+        self.assertEqual(K, transport._K)
+        self.assertEqual(H, hexlify(transport._H).upper())
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertTrue(transport._activated)
+
     def test_kex_group16_sha512_client(self):
         transport = FakeTransport()
         transport.server_mode = False
@@ -573,6 +594,27 @@ class KexTest(unittest.TestCase):
         self.assertEqual((b"fake-host-key", b"fake-sig"), transport._verify)
         self.assertTrue(transport._activated)
 
+    def test_kex_group16_sha512_server(self):
+        transport = FakeTransport()
+        transport.server_mode = True
+        kex = KexGroup16SHA512(transport)
+        kex.start_kex()
+        self.assertEqual(
+            (paramiko.kex_group1._MSG_KEXDH_INIT,), transport._expect
+        )
+
+        msg = Message()
+        msg.add_mpint(69)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_group1._MSG_KEXDH_INIT, msg)
+        K = 933242830095376162107925500057692534838883186615567574891154103836907630698358649443101764908667358576734565553213003142941996368306996312915844839972197961603283544950658467545799914435739152351344917376359963584614213874232577733869049670230112638724993540996854599166318001059065780674008011575015459772051180901213815080343343801745386220342919837913506966863570473712948197760657442974564354432738520446202131551650771882909329069340612274196233658123593466135642819578182367229641847749149740891990379052266213711500434128970973602206842980669193719602075489724202241641553472106310932258574377789863734311328542715212248147206865762697424822447603031087553480483833829498375309975229907460562402877655519980113688369262871485777790149373908739910846630414678346163764464587129010141922982925829457954376352735653834300282864445132624993186496129911208133529828461690634463092007726349795944930302881758403402084584307180896465875803621285362317770276493727205689466142632599776710824902573926951951209239626732358074877997756011804454926541386215567756538832824717436605031489511654178384081883801272314328403020205577714999460724519735573055540814037716770051316113795603990199374791348798218428912977728347485489266146775472  # noqa
+        H = b"F97BB05A572A663688CA7EA1AA812D3C82EE6C8FA9D4B1D69435783D931157F199909EA38B003E4E4385C8861183CBFF0CF0EF1433A8B3C69AB4DD9420FCC85F"
+        x = b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noqa
+        self.assertEqual(K, transport._K)
+        self.assertEqual(H, hexlify(transport._H).upper())
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertTrue(transport._activated)
+
     @pytest.mark.skipif("not KexCurve25519.is_available()")
     def test_kex_c25519_client(self):
         K = 71294722834835117201316639182051104803802881348227506835068888449366462300724  # noqa