Updated notes on OpenSSH default key exchanges. (#258)

When evaluating policy compliance, use less-than operator so keys bigger
than expected (and hence very often better) don't fail policy
evaulation. This change reduces the amount of false-positives and allows
for more flexibility when hardening SSH installations.

Signed-off-by: szubersk <szuberskidamian@gmail.com>

README.md

@@ -191,6 +191,7 @@ For convenience, a web front-end on top of the command-line tool is available at
  - Snap builds are now architecture-independent.
  - Changed Docker base image from `python:3-slim` to `python:3-alpine`, resulting in a 59% reduction in image size; credit [Daniel Thamdrup](https://github.com/dallemon).
  - Custom policies now support the `allow_algorithm_subset_and_reordering` directive to allow targets to pass with a subset and/or re-ordered list of host keys, kex, ciphers, and MACs.  This allows for the creation of a baseline policy where targets can optionally implement stricter controls; partial credit [yannik1015](https://github.com/yannik1015).
+ - Custom policies now support the `allow_larger_keys` directive to allow targets to pass with larger host keys, CA keys, and Diffie-Hellman keys.  This allows for the creation of a baseline policy where targets can optionally implement stricter controls; partial credit [Damian Szuberski](https://github.com/szubersk).
  - Added 1 new key exchange algorithm: `gss-nistp384-sha384-*`.
 
 ### v3.1.0 (2023-12-20)

docker_test.sh

@@ -790,6 +790,9 @@ run_custom_policy_test "config2" "test15" "${PROGRAM_RETVAL_GOOD}"
 # Failing test with algorithm subset matching.
 run_custom_policy_test "config2" "test16" "${PROGRAM_RETVAL_FAILURE}"
 
+# Passing test with larger key matching.
+run_custom_policy_test "config2" "test17" "${PROGRAM_RETVAL_GOOD}"
+
 # Failing test for built-in OpenSSH 8.0p1 server policy (RSA host key size is 3072 instead of 4096).
 run_builtin_policy_test "Hardened OpenSSH Server v8.0 (version 4)" "8.0p1" "test1" "-o HostKeyAlgorithms=rsa-sha2-512,rsa-sha2-256,ssh-ed25519 -o KexAlgorithms=curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256 -o Ciphers=chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr -o MACs=hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com" "${PROGRAM_RETVAL_FAILURE}"
 

src/ssh_audit/policy.py

@@ -55,6 +55,7 @@ class Policy:
         self._dh_modulus_sizes: Optional[Dict[str, int]] = None
         self._server_policy = True
         self._allow_algorithm_subset_and_reordering = False
+        self._allow_larger_keys = False
         self._errors: List[Any] = []
 
         self._name_and_version: str = ''
@@ -114,7 +115,7 @@ class Policy:
             key = key.strip()
             val = val.strip()
 
-            if key not in ['name', 'version', 'banner', 'compressions', 'host keys', 'optional host keys', 'key exchanges', 'ciphers', 'macs', 'client policy', 'host_key_sizes', 'dh_modulus_sizes', 'allow_algorithm_subset_and_reordering'] and not key.startswith('hostkey_size_') and not key.startswith('cakey_size_') and not key.startswith('dh_modulus_size_'):
+            if key not in ['name', 'version', 'banner', 'compressions', 'host keys', 'optional host keys', 'key exchanges', 'ciphers', 'macs', 'client policy', 'host_key_sizes', 'dh_modulus_sizes', 'allow_algorithm_subset_and_reordering', 'allow_larger_keys'] and not key.startswith('hostkey_size_') and not key.startswith('cakey_size_') and not key.startswith('dh_modulus_size_'):
                 raise ValueError("invalid field found in policy: %s" % line)
 
             if key in ['name', 'banner']:
@@ -209,6 +210,8 @@ class Policy:
                 self._server_policy = False
             elif key == 'allow_algorithm_subset_and_reordering' and val.lower() == 'true':
                 self._allow_algorithm_subset_and_reordering = True
+            elif key == 'allow_larger_keys' and val.lower() == 'true':
+                self._allow_larger_keys = True
 
         if self._name is None:
             raise ValueError('The policy does not have a name field.')
@@ -296,9 +299,12 @@ name = "Custom Policy (based on %s on %s)"
 # The version of this policy (displayed in the output during scans).  Not parsed, and may be any value, including strings.
 version = 1
 
-# When false, host keys, kex, ciphers, and MAC lists must match exactly.  When true, the target host may support a subset of the specified algorithms and/or algorithms may appear in a different order; this is useful for specifying a baseline and allowing some hosts the option to implement stricter controls.
+# When false, host keys, kex, ciphers, and MAC lists must match exactly.  When true, the target host may support a subset of the specified algorithms and/or algorithms may appear in a different order; this feature is useful for specifying a baseline and allowing some hosts the option to implement stricter controls.
 allow_algorithm_subset_and_reordering = false
 
+# When false, host keys, CA keys, and Diffie-Hellman key sizes must exactly match what's specified in this policy.  When true, target systems are allowed to have larger keys; this feature is useful for specifying a baseline and allowing some hosts the option to implement stricter controls.
+allow_larger_keys = false
+
 # The banner that must match exactly.  Commented out to ignore banners, since minor variability in the banner is sometimes normal.
 # banner = "%s"
 
@@ -367,11 +373,12 @@ macs = %s
             hostkey_types = list(self._hostkey_sizes.keys())
             hostkey_types.sort()  # Sorted to make testing output repeatable.
             for hostkey_type in hostkey_types:
-                expected_hostkey_size = self._hostkey_sizes[hostkey_type]['hostkey_size']
+                expected_hostkey_size = cast(int, self._hostkey_sizes[hostkey_type]['hostkey_size'])
                 server_host_keys = kex.host_keys()
                 if hostkey_type in server_host_keys:
-                    actual_hostkey_size = server_host_keys[hostkey_type]['hostkey_size']
-                    if actual_hostkey_size != expected_hostkey_size:
+                    actual_hostkey_size = cast(int, server_host_keys[hostkey_type]['hostkey_size'])
+                    if (self._allow_larger_keys and actual_hostkey_size < expected_hostkey_size) or \
+                       (not self._allow_larger_keys and actual_hostkey_size != expected_hostkey_size):
                         ret = False
                         self._append_error('Host key (%s) sizes' % hostkey_type, [str(expected_hostkey_size)], None, [str(actual_hostkey_size)])
 
@@ -387,7 +394,8 @@ macs = %s
                             ret = False
                             self._append_error('CA signature type', [expected_ca_key_type], None, [actual_ca_key_type])
                         # Ensure that the actual and expected signature sizes match.
-                        elif actual_ca_key_size != expected_ca_key_size:
+                        elif (self._allow_larger_keys and actual_ca_key_size < expected_ca_key_size) or \
+                             (not self._allow_larger_keys and actual_ca_key_size != expected_ca_key_size):
                             ret = False
                             self._append_error('CA signature size (%s)' % actual_ca_key_type, [str(expected_ca_key_size)], None, [str(actual_ca_key_size)])
 
@@ -446,7 +454,8 @@ macs = %s
                 expected_dh_modulus_size = self._dh_modulus_sizes[dh_modulus_type]
                 if dh_modulus_type in kex.dh_modulus_sizes():
                     actual_dh_modulus_size = kex.dh_modulus_sizes()[dh_modulus_type]
-                    if expected_dh_modulus_size != actual_dh_modulus_size:
+                    if (self._allow_larger_keys and actual_dh_modulus_size < expected_dh_modulus_size) or \
+                       (not self._allow_larger_keys and actual_dh_modulus_size != expected_dh_modulus_size):
                         ret = False
                         self._append_error('Group exchange (%s) modulus sizes' % dh_modulus_type, [str(expected_dh_modulus_size)], None, [str(actual_dh_modulus_size)])
 

src/ssh_audit/ssh2_kexdb.py

@@ -62,7 +62,8 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
     WARN_TAG_SIZE_96 = 'using small 96-bit tag size'
 
     INFO_DEFAULT_OPENSSH_CIPHER = 'default cipher since OpenSSH 6.9'
-    INFO_DEFAULT_OPENSSH_KEX_64_TO_89 = 'default key exchange from OpenSSH 6.4 to 8.9'
+    INFO_DEFAULT_OPENSSH_KEX_65_TO_73 = 'default key exchange from OpenSSH 6.5 to 7.3'
+    INFO_DEFAULT_OPENSSH_KEX_74_TO_89 = 'default key exchange from OpenSSH 7.4 to 8.9'
     INFO_DEFAULT_OPENSSH_KEX_90 = 'default key exchange since OpenSSH 9.0'
     INFO_DEPRECATED_IN_OPENSSH88 = 'deprecated in OpenSSH 8.8: https://www.openssh.com/txt/release-8.8'
     INFO_DISABLED_IN_DBEAR67 = 'disabled in Dropbear SSH 2015.67'
@@ -82,8 +83,8 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
         # Format: 'algorithm_name': [['version_first_appeared_in'], [reason_for_failure1, reason_for_failure2, ...], [warning1, warning2, ...], [info1, info2, ...]]
         'kex': {
             'Curve25519SHA256': [[]],
-            'curve25519-sha256': [['7.4,d2018.76'], [], [], [INFO_DEFAULT_OPENSSH_KEX_64_TO_89]],
-            'curve25519-sha256@libssh.org': [['6.4,d2013.62,l10.6.0'], [], [], [INFO_DEFAULT_OPENSSH_KEX_64_TO_89]],
+            'curve25519-sha256': [['7.4,d2018.76'], [], [], [INFO_DEFAULT_OPENSSH_KEX_74_TO_89]],
+            'curve25519-sha256@libssh.org': [['6.4,d2013.62,l10.6.0'], [], [], [INFO_DEFAULT_OPENSSH_KEX_65_TO_73]],
             'curve448-sha512': [[]],
             'curve448-sha512@libssh.org': [[]],
             'diffie-hellman-group14-sha1': [['3.9,d0.53,l10.6.0'], [FAIL_SHA1], [WARN_2048BIT_MODULUS]],
@@ -223,7 +224,7 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
             'null': [[], [FAIL_PLAINTEXT]],
             'pgp-sign-dss': [[], [FAIL_1024BIT_MODULUS]],
             'pgp-sign-rsa': [[], [FAIL_1024BIT_MODULUS]],
-            'rsa-sha2-256': [['7.2']],
+            'rsa-sha2-256': [['7.2,d2020.79']],
             'rsa-sha2-256-cert-v01@openssh.com': [['7.8']],
             'rsa-sha2-512': [['7.2']],
             'rsa-sha2-512-cert-v01@openssh.com': [['7.8']],
@@ -242,7 +243,7 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
             'ssh-dss-sha256@ssh.com': [[], [FAIL_1024BIT_MODULUS]],
             'ssh-dss-sha384@ssh.com': [[], [FAIL_1024BIT_MODULUS]],
             'ssh-dss-sha512@ssh.com': [[], [FAIL_1024BIT_MODULUS]],
-            'ssh-ed25519': [['6.5,l10.7.0']],
+            'ssh-ed25519': [['6.5,d2020.79,l10.7.0']],
             'ssh-ed25519-cert-v01@openssh.com': [['6.5']],
             'ssh-ed448': [[]],
             'ssh-ed448-cert-v01@openssh.com': [[], [], [], [INFO_NEVER_IMPLEMENTED_IN_OPENSSH]],
@@ -335,7 +336,7 @@ class SSH2_KexDB:  # pylint: disable=too-few-public-methods
             'cast128-ecb': [[], [FAIL_CAST], [WARN_CIPHER_MODE]],
             'cast128-ofb': [[], [FAIL_CAST], [WARN_CIPHER_MODE]],
             'chacha20-poly1305': [[], [], [], [INFO_DEFAULT_OPENSSH_CIPHER]],
-            'chacha20-poly1305@openssh.com': [['6.5'], [], [], [INFO_DEFAULT_OPENSSH_CIPHER]],
+            'chacha20-poly1305@openssh.com': [['6.5,d2020.79'], [], [], [INFO_DEFAULT_OPENSSH_CIPHER]],
             'crypticore128@ssh.com': [[], [FAIL_UNPROVEN]],
             'des-cbc': [[], [FAIL_DES], [WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],
             'des-cfb': [[], [FAIL_DES], [WARN_CIPHER_MODE, WARN_BLOCK_SIZE]],

test/docker/expected_results/dropbear_2019.78_test1.json

@@ -96,7 +96,7 @@
             "algorithm": "curve25519-sha256",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 7.4 to 8.9",
                     "available since OpenSSH 7.4, Dropbear SSH 2018.76"
                 ]
             }
@@ -105,7 +105,7 @@
             "algorithm": "curve25519-sha256@libssh.org",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 6.5 to 7.3",
                     "available since OpenSSH 6.4, Dropbear SSH 2013.62"
                 ]
             }

test/docker/expected_results/dropbear_2019.78_test1.txt

@@ -6,9 +6,9 @@
 
 # key exchange algorithms
 (kex) curve25519-sha256              -- [info] available since OpenSSH 7.4, Dropbear SSH 2018.76
-                                     `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                     `- [info] default key exchange from OpenSSH 7.4 to 8.9
 (kex) curve25519-sha256@libssh.org   -- [info] available since OpenSSH 6.4, Dropbear SSH 2013.62
-                                     `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                     `- [info] default key exchange from OpenSSH 6.5 to 7.3
 (kex) ecdh-sha2-nistp521             -- [fail] using elliptic curves that are suspected as being backdoored by the U.S. National Security Agency
                                      `- [info] available since OpenSSH 5.7, Dropbear SSH 2013.62
 (kex) ecdh-sha2-nistp384             -- [fail] using elliptic curves that are suspected as being backdoored by the U.S. National Security Agency

test/docker/expected_results/openssh_8.0p1_custom_policy_test17.json

@@ -0,0 +1,6 @@
+{
+    "errors": [],
+    "host": "localhost",
+    "passed": true,
+    "policy": "Docker policy: test17 (version 1)"
+}

test/docker/expected_results/openssh_8.0p1_custom_policy_test17.txt

@@ -0,0 +1,3 @@
+Host:   localhost:2222
+Policy: Docker policy: test17 (version 1)
+Result: ✔ Passed

test/docker/expected_results/openssh_8.0p1_test1.json

@@ -40,7 +40,7 @@
             "notes": {
                 "info": [
                     "default cipher since OpenSSH 6.9",
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ],
                 "warn": [
                     "vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation"
@@ -115,7 +115,7 @@
             "algorithm": "curve25519-sha256",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 7.4 to 8.9",
                     "available since OpenSSH 7.4, Dropbear SSH 2018.76"
                 ]
             }
@@ -124,7 +124,7 @@
             "algorithm": "curve25519-sha256@libssh.org",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 6.5 to 7.3",
                     "available since OpenSSH 6.4, Dropbear SSH 2013.62"
                 ]
             }
@@ -229,7 +229,7 @@
             "keysize": 3072,
             "notes": {
                 "info": [
-                    "available since OpenSSH 7.2"
+                    "available since OpenSSH 7.2, Dropbear SSH 2020.79"
                 ]
             }
         },
@@ -264,7 +264,7 @@
             "algorithm": "ssh-ed25519",
             "notes": {
                 "info": [
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ]
             }
         }

test/docker/expected_results/openssh_8.0p1_test1.txt

@@ -1,7 +1,7 @@
 # general
 (gen) banner: SSH-2.0-OpenSSH_8.0
 (gen) software: OpenSSH 8.0
-(gen) compatibility: OpenSSH 7.4+, Dropbear SSH 2018.76+
+(gen) compatibility: OpenSSH 7.4+, Dropbear SSH 2020.79+
 (gen) compression: enabled (zlib@openssh.com)
 
 # security
@@ -12,9 +12,9 @@
 
 # key exchange algorithms
 (kex) curve25519-sha256                     -- [info] available since OpenSSH 7.4, Dropbear SSH 2018.76
-                                            `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                            `- [info] default key exchange from OpenSSH 7.4 to 8.9
 (kex) curve25519-sha256@libssh.org          -- [info] available since OpenSSH 6.4, Dropbear SSH 2013.62
-                                            `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                            `- [info] default key exchange from OpenSSH 6.5 to 7.3
 (kex) ecdh-sha2-nistp256                    -- [fail] using elliptic curves that are suspected as being backdoored by the U.S. National Security Agency
                                             `- [info] available since OpenSSH 5.7, Dropbear SSH 2013.62
 (kex) ecdh-sha2-nistp384                    -- [fail] using elliptic curves that are suspected as being backdoored by the U.S. National Security Agency
@@ -33,18 +33,18 @@
 
 # host-key algorithms
 (key) rsa-sha2-512 (3072-bit)               -- [info] available since OpenSSH 7.2
-(key) rsa-sha2-256 (3072-bit)               -- [info] available since OpenSSH 7.2
+(key) rsa-sha2-256 (3072-bit)               -- [info] available since OpenSSH 7.2, Dropbear SSH 2020.79
 (key) ssh-rsa (3072-bit)                    -- [fail] using broken SHA-1 hash algorithm
                                             `- [info] available since OpenSSH 2.5.0, Dropbear SSH 0.28
                                             `- [info] deprecated in OpenSSH 8.8: https://www.openssh.com/txt/release-8.8
 (key) ecdsa-sha2-nistp256                   -- [fail] using elliptic curves that are suspected as being backdoored by the U.S. National Security Agency
                                             `- [warn] using weak random number generator could reveal the key
                                             `- [info] available since OpenSSH 5.7, Dropbear SSH 2013.62
-(key) ssh-ed25519                           -- [info] available since OpenSSH 6.5
+(key) ssh-ed25519                           -- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
 
 # encryption algorithms (ciphers)
 (enc) chacha20-poly1305@openssh.com         -- [warn] vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation
-                                            `- [info] available since OpenSSH 6.5
+                                            `- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
                                             `- [info] default cipher since OpenSSH 6.9
 (enc) aes128-ctr                            -- [info] available since OpenSSH 3.7, Dropbear SSH 0.52
 (enc) aes192-ctr                            -- [info] available since OpenSSH 3.7

test/docker/expected_results/openssh_8.0p1_test2.json

@@ -40,7 +40,7 @@
             "notes": {
                 "info": [
                     "default cipher since OpenSSH 6.9",
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ],
                 "warn": [
                     "vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation"
@@ -105,7 +105,7 @@
             "algorithm": "curve25519-sha256",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 7.4 to 8.9",
                     "available since OpenSSH 7.4, Dropbear SSH 2018.76"
                 ]
             }
@@ -114,7 +114,7 @@
             "algorithm": "curve25519-sha256@libssh.org",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 6.5 to 7.3",
                     "available since OpenSSH 6.4, Dropbear SSH 2013.62"
                 ]
             }
@@ -209,7 +209,7 @@
             "algorithm": "ssh-ed25519",
             "notes": {
                 "info": [
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ]
             }
         },

test/docker/expected_results/openssh_8.0p1_test2.txt

@@ -1,7 +1,7 @@
 # general
 (gen) banner: SSH-2.0-OpenSSH_8.0
 (gen) software: OpenSSH 8.0
-(gen) compatibility: OpenSSH 7.4+, Dropbear SSH 2018.76+
+(gen) compatibility: OpenSSH 7.4+, Dropbear SSH 2020.79+
 (gen) compression: enabled (zlib@openssh.com)
 
 # security
@@ -12,9 +12,9 @@
 
 # key exchange algorithms
 (kex) curve25519-sha256                     -- [info] available since OpenSSH 7.4, Dropbear SSH 2018.76
-                                            `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                            `- [info] default key exchange from OpenSSH 7.4 to 8.9
 (kex) curve25519-sha256@libssh.org          -- [info] available since OpenSSH 6.4, Dropbear SSH 2013.62
-                                            `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                            `- [info] default key exchange from OpenSSH 6.5 to 7.3
 (kex) ecdh-sha2-nistp256                    -- [fail] using elliptic curves that are suspected as being backdoored by the U.S. National Security Agency
                                             `- [info] available since OpenSSH 5.7, Dropbear SSH 2013.62
 (kex) ecdh-sha2-nistp384                    -- [fail] using elliptic curves that are suspected as being backdoored by the U.S. National Security Agency
@@ -32,12 +32,12 @@
                                             `- [info] available since OpenSSH 3.9, Dropbear SSH 0.53
 
 # host-key algorithms
-(key) ssh-ed25519                           -- [info] available since OpenSSH 6.5
+(key) ssh-ed25519                           -- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
 (key) ssh-ed25519-cert-v01@openssh.com (256-bit cert/256-bit ssh-ed25519 CA) -- [info] available since OpenSSH 6.5
 
 # encryption algorithms (ciphers)
 (enc) chacha20-poly1305@openssh.com         -- [warn] vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation
-                                            `- [info] available since OpenSSH 6.5
+                                            `- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
                                             `- [info] default cipher since OpenSSH 6.9
 (enc) aes128-ctr                            -- [info] available since OpenSSH 3.7, Dropbear SSH 0.52
 (enc) aes192-ctr                            -- [info] available since OpenSSH 3.7

test/docker/expected_results/openssh_8.0p1_test3.json

@@ -40,7 +40,7 @@
             "notes": {
                 "info": [
                     "default cipher since OpenSSH 6.9",
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ],
                 "warn": [
                     "vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation"
@@ -105,7 +105,7 @@
             "algorithm": "curve25519-sha256",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 7.4 to 8.9",
                     "available since OpenSSH 7.4, Dropbear SSH 2018.76"
                 ]
             }
@@ -114,7 +114,7 @@
             "algorithm": "curve25519-sha256@libssh.org",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 6.5 to 7.3",
                     "available since OpenSSH 6.4, Dropbear SSH 2013.62"
                 ]
             }
@@ -135,7 +135,7 @@
             "algorithm": "ssh-ed25519",
             "notes": {
                 "info": [
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ]
             }
         }

test/docker/expected_results/openssh_8.0p1_test3.txt

@@ -1,7 +1,7 @@
 # general
 (gen) banner: SSH-2.0-OpenSSH_8.0
 (gen) software: OpenSSH 8.0
-(gen) compatibility: OpenSSH 7.4+, Dropbear SSH 2018.76+
+(gen) compatibility: OpenSSH 7.4+, Dropbear SSH 2020.79+
 (gen) compression: enabled (zlib@openssh.com)
 
 # security
@@ -12,18 +12,18 @@
 
 # key exchange algorithms
 (kex) curve25519-sha256                     -- [info] available since OpenSSH 7.4, Dropbear SSH 2018.76
-                                            `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                            `- [info] default key exchange from OpenSSH 7.4 to 8.9
 (kex) curve25519-sha256@libssh.org          -- [info] available since OpenSSH 6.4, Dropbear SSH 2013.62
-                                            `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                            `- [info] default key exchange from OpenSSH 6.5 to 7.3
 (kex) diffie-hellman-group-exchange-sha256 (4096-bit) -- [info] available since OpenSSH 4.4
                                                       `- [info] OpenSSH's GEX fallback mechanism was triggered during testing. Very old SSH clients will still be able to create connections using a 2048-bit modulus, though modern clients will use 4096. This can only be disabled by recompiling the code (see https://github.com/openssh/openssh-portable/blob/V_9_4/dh.c#L477).
 
 # host-key algorithms
-(key) ssh-ed25519                           -- [info] available since OpenSSH 6.5
+(key) ssh-ed25519                           -- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
 
 # encryption algorithms (ciphers)
 (enc) chacha20-poly1305@openssh.com         -- [warn] vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation
-                                            `- [info] available since OpenSSH 6.5
+                                            `- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
                                             `- [info] default cipher since OpenSSH 6.9
 (enc) aes256-gcm@openssh.com                -- [info] available since OpenSSH 6.2
 (enc) aes128-gcm@openssh.com                -- [info] available since OpenSSH 6.2

test/docker/expected_results/tinyssh_20190101_test1.json

@@ -18,7 +18,7 @@
             "notes": {
                 "info": [
                     "default cipher since OpenSSH 6.9",
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ],
                 "warn": [
                     "vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation"
@@ -43,7 +43,7 @@
             "algorithm": "curve25519-sha256",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 7.4 to 8.9",
                     "available since OpenSSH 7.4, Dropbear SSH 2018.76"
                 ]
             }
@@ -52,7 +52,7 @@
             "algorithm": "curve25519-sha256@libssh.org",
             "notes": {
                 "info": [
-                    "default key exchange from OpenSSH 6.4 to 8.9",
+                    "default key exchange from OpenSSH 6.5 to 7.3",
                     "available since OpenSSH 6.4, Dropbear SSH 2013.62"
                 ]
             }
@@ -75,7 +75,7 @@
             "algorithm": "ssh-ed25519",
             "notes": {
                 "info": [
-                    "available since OpenSSH 6.5"
+                    "available since OpenSSH 6.5, Dropbear SSH 2020.79"
                 ]
             }
         }

test/docker/expected_results/tinyssh_20190101_test1.txt

@@ -1,23 +1,23 @@
 # general
 (gen) software: TinySSH noversion
-(gen) compatibility: OpenSSH 8.0-8.4, Dropbear SSH 2018.76+
+(gen) compatibility: OpenSSH 8.0-8.4, Dropbear SSH 2020.79+
 (gen) compression: disabled
 
 # key exchange algorithms
 (kex) curve25519-sha256                       -- [info] available since OpenSSH 7.4, Dropbear SSH 2018.76
-                                              `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                              `- [info] default key exchange from OpenSSH 7.4 to 8.9
 (kex) curve25519-sha256@libssh.org            -- [info] available since OpenSSH 6.4, Dropbear SSH 2013.62
-                                              `- [info] default key exchange from OpenSSH 6.4 to 8.9
+                                              `- [info] default key exchange from OpenSSH 6.5 to 7.3
 (kex) sntrup4591761x25519-sha512@tinyssh.org  -- [warn] using experimental algorithm
                                               `- [info] available since OpenSSH 8.0
                                               `- [info] the sntrup4591761 algorithm was withdrawn, as it may not provide strong post-quantum security
 
 # host-key algorithms
-(key) ssh-ed25519                             -- [info] available since OpenSSH 6.5
+(key) ssh-ed25519                             -- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
 
 # encryption algorithms (ciphers)
 (enc) chacha20-poly1305@openssh.com           -- [warn] vulnerable to the Terrapin attack (CVE-2023-48795), allowing message prefix truncation
-                                              `- [info] available since OpenSSH 6.5
+                                              `- [info] available since OpenSSH 6.5, Dropbear SSH 2020.79
                                               `- [info] default cipher since OpenSSH 6.9
 
 # message authentication code algorithms

test/docker/policies/policy_test17.txt

@@ -0,0 +1,15 @@
+#
+# Docker policy: test17
+#
+
+name = "Docker policy: test17"
+version = 1
+allow_larger_keys = true
+banner = "SSH-2.0-OpenSSH_8.0"
+compressions = none, zlib@openssh.com
+host keys = rsa-sha2-512, rsa-sha2-256, ssh-rsa, ecdsa-sha2-nistp256, ssh-ed25519
+key exchanges = curve25519-sha256, curve25519-sha256@libssh.org, ecdh-sha2-nistp256, ecdh-sha2-nistp384, ecdh-sha2-nistp521, diffie-hellman-group-exchange-sha256, diffie-hellman-group16-sha512, diffie-hellman-group18-sha512, diffie-hellman-group14-sha256, diffie-hellman-group14-sha1
+ciphers = chacha20-poly1305@openssh.com, aes128-ctr, aes192-ctr, aes256-ctr, aes128-gcm@openssh.com, aes256-gcm@openssh.com
+macs = umac-64-etm@openssh.com, umac-128-etm@openssh.com, hmac-sha2-256-etm@openssh.com, hmac-sha2-512-etm@openssh.com, hmac-sha1-etm@openssh.com, umac-64@openssh.com, umac-128@openssh.com, hmac-sha2-256, hmac-sha2-512, hmac-sha1
+host_key_sizes = {"ssh-rsa": {"hostkey_size": 2048}, "rsa-sha2-256": {"hostkey_size": 2048}, "rsa-sha2-512": {"hostkey_size": 2048}, "ssh-ed25519": {"hostkey_size": 256}}
+dh_modulus_sizes = {"diffie-hellman-group-exchange-sha256": 2048}

test/test_policy.py

@@ -297,7 +297,7 @@ macs = mac_alg1, mac_alg2, mac_alg3'''
         pol_data = pol_data.replace(date.today().strftime('%Y/%m/%d'), '[todays date]')
 
         # Instead of writing out the entire expected policy--line by line--just check that it has the expected hash.
-        assert hashlib.sha256(pol_data.encode('ascii')).hexdigest() == '4b504b799f6b964a20ccbe8af7edd26c7b5f0e0b98070e754ea41dccdace33b4'
+        assert hashlib.sha256(pol_data.encode('ascii')).hexdigest() == 'fb84bce442cff2bce9bf653d6373a8a938e3bfcfbd1e876f51a08c1842df3cff'
 
 
     def test_policy_evaluate_passing_1(self):