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Fixed pylint errors, consolidated error checking for granular GEX tests, renamed functions for better readability.

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Joe Testa 2022-03-13 20:58:22 -04:00
parent 19f192d21f
commit 11905ed44a
4 changed files with 51 additions and 65 deletions
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1
README.md
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@ -172,6 +172,7 @@ For convenience, a web front-end on top of the command-line tool is available at
## ChangeLog
### v2.6.0-dev
- Added `-g` and `--gex-test` for granular GEX modulus size tests; credit [Adam Russell](https://github.com/thecliguy).
- Snap packages now print more user-friendly error messages when permission errors are encountered.
- JSON 'target' field now always includes port number; credit [tomatohater1337](https://github.com/tomatohater1337).
- Added 24 new key exchanges: `ecdh-sha2-1.3.132.0.1`, `ecdh-sha2-1.2.840.10045.3.1.1`, `ecdh-sha2-1.3.132.0.33`, `ecdh-sha2-1.3.132.0.26`, `ecdh-sha2-1.3.132.0.27`, `ecdh-sha2-1.2.840.10045.3.1.7`, `ecdh-sha2-1.3.132.0.16`, `ecdh-sha2-1.3.132.0.34`, `ecdh-sha2-1.3.132.0.36`, `ecdh-sha2-1.3.132.0.37`, `ecdh-sha2-1.3.132.0.35`, `ecdh-sha2-1.3.132.0.38`, `ecdh-sha2-4MHB+NBt3AlaSRQ7MnB4cg==`, `ecdh-sha2-5pPrSUQtIaTjUSt5VZNBjg==`, `ecdh-sha2-VqBg4QRPjxx1EXZdV0GdWQ==`, `ecdh-sha2-zD/b3hu/71952ArpUG4OjQ==`, `ecdh-sha2-qCbG5Cn/jjsZ7nBeR7EnOA==`, `ecdh-sha2-9UzNcgwTlEnSCECZa7V1mw==`, `ecdh-sha2-wiRIU8TKjMZ418sMqlqtvQ==`, `ecdh-sha2-qcFQaMAMGhTziMT0z+Tuzw==`, `ecdh-sha2-m/FtSAmrV4j/Wy6RVUaK7A==`, `ecdh-sha2-D3FefCjYoJ/kfXgAyLddYA==`, `ecdh-sha2-h/SsxnLCtRBh7I9ATyeB3A==`, `ecdh-sha2-mNVwCXAoS1HGmHpLvBC94w==`.

40
src/ssh_audit/gextest.py
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@ -21,13 +21,12 @@
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
"""
import traceback
# pylint: disable=unused-import
from typing import Dict, List, Set, Sequence, Tuple, Iterable # noqa: F401
from typing import Callable, Optional, Union, Any # noqa: F401
import traceback
from ssh_audit.kexdh import KexGroupExchange_SHA1, KexGroupExchange_SHA256
from ssh_audit.ssh2_kexdb import SSH2_KexDB
from ssh_audit.ssh2_kex import SSH2_Kex
@ -71,11 +70,10 @@ class GEXTest:
return True
# Tests for modulus size in bits against the specified target.
@staticmethod
def modulus_size_test(out: 'OutputBuffer', s: 'SSH_Socket', kex: 'SSH2_Kex', bits_min: int, bits_pref: int, bits_max: int, modulus_dict: Dict[str, List[int]]) -> int:
def granular_modulus_size_test(out: 'OutputBuffer', s: 'SSH_Socket', kex: 'SSH2_Kex', bits_min: int, bits_pref: int, bits_max: int, modulus_dict: Dict[str, List[int]]) -> int:
'''
Tests for modulus size in bits against the target target.
Tests for granular modulus sizes.
Builds a dictionary, where a key represents a DH algorithm name and the
values are the modulus sizes (in bits) that have been returned by the
target server.
@ -89,10 +87,6 @@ class GEXTest:
out.d("Bits Pref: " + str(bits_pref))
out.d("Bits Max: " + str(bits_max))
if all(x < 0 for x in (bits_min, bits_pref, bits_max)):
out.fail("min, pref and max values cannot be negative.")
return exitcodes.FAILURE
GEX_ALGS = {
'diffie-hellman-group-exchange-sha1': KexGroupExchange_SHA1,
'diffie-hellman-group-exchange-sha256': KexGroupExchange_SHA256,
@ -100,11 +94,11 @@ class GEXTest:
# Check if the server supports any of the group-exchange
# algorithms. If so, test each one.
for gex_alg in GEX_ALGS:
for gex_alg, kex_group_class in GEX_ALGS.items():
if gex_alg not in kex.kex_algorithms:
out.d('Server does not support the algorithm "' + gex_alg + '".', write_now=True)
else:
kex_group = GEX_ALGS[gex_alg]()
kex_group = kex_group_class()
out.d('Preparing to perform DH group exchange using ' + gex_alg + ' with min, pref and max modulus sizes of ' + str(bits_min) + ' bits, ' + str(bits_pref) + ' bits and ' + str(bits_max) + ' bits...', write_now=True)
# It has been observed that reconnecting to some SSH servers
@ -121,11 +115,8 @@ class GEXTest:
kex_group.recv_reply(s, False)
modulus_size_returned = kex_group.get_dh_modulus_size()
out.d('Modulus size returned by server: ' + str(modulus_size_returned) + ' bits', write_now=True)
except Exception as e:
out.d('[exception] ' + str(e), write_now=True)
# import traceback
# print(traceback.format_exc())
pass
except Exception:
out.d('[exception] ' + str(traceback.format_exc()), write_now=True)
finally:
# The server is in a state that is not re-testable,
# so there's nothing else to do with this open
@ -159,8 +150,7 @@ class GEXTest:
# algorithms. If so, test each one.
for gex_alg, kex_group_class in GEX_ALGS.items():
if gex_alg in kex.kex_algorithms:
weak_sizes = 512, 1024, 1536
out.d('Preparing to perform DH group exchange using ' + gex_alg + ' with min, pref and max modulus sizes of ' + str(weak_sizes[0]) + ' bits, ' + str(weak_sizes[1]) + ' bits and ' + str(weak_sizes[2]) + ' bits...', write_now=True)
out.d('Preparing to perform DH group exchange using ' + gex_alg + ' with min, pref and max modulus sizes of 512 bits, 1024 bits and 1536 bits...', write_now=True)
if GEXTest.reconnect(out, s, kex, gex_alg) is False:
break
@ -170,7 +160,7 @@ class GEXTest:
# First try a range of weak sizes.
try:
kex_group.send_init_gex(s, weak_sizes[0], weak_sizes[1], weak_sizes[2])
kex_group.send_init_gex(s, 512, 1024, 1536)
kex_group.recv_reply(s, False)
# Its been observed that servers will return a group
@ -179,9 +169,8 @@ class GEXTest:
smallest_modulus = kex_group.get_dh_modulus_size()
out.d('Modulus size returned by server: ' + str(smallest_modulus) + ' bits', write_now=True)
except Exception as e:
out.d('[exception] ' + str(e), write_now=True)
pass
except Exception:
out.d('[exception] ' + str(traceback.format_exc()), write_now=True)
finally:
s.close()
@ -205,11 +194,8 @@ class GEXTest:
kex_group.recv_reply(s, False)
smallest_modulus = kex_group.get_dh_modulus_size()
out.d('Modulus size returned by server: ' + str(smallest_modulus) + ' bits', write_now=True)
except Exception as e:
out.d('[exception] ' + str(e), write_now=True)
# import traceback
# print(traceback.format_exc())
pass
except Exception:
out.d('[exception] ' + str(traceback.format_exc()), write_now=True)
finally:
# The server is in a state that is not re-testable,
# so there's nothing else to do with this open

52
src/ssh_audit/ssh_audit.py
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@ -87,7 +87,7 @@ def usage(err: Optional[str] = None) -> None:
uout.info(' -b, --batch batch output')
uout.info(' -c, --client-audit starts a server on port 2222 to audit client\n software config (use -p to change port;\n use -t to change timeout)')
uout.info(' -d, --debug debug output')
uout.info(' -g, --gex-test=<n[,n,...] | min:pref:max[,min:pref:max,...] | n-n[:step]> dh gex modulus size test')
uout.info(' -g, --gex-test=<x[,y,...] | min:pref:max[,min:pref:max,...] | x-y[:step]> dh gex modulus size test')
uout.info(' -j, --json JSON output (use -jj to enable indents)')
uout.info(' -l, --level=<level> minimum output level (info|warn|fail)')
uout.info(' -L, --list-policies list all the official, built-in policies')
@ -654,10 +654,29 @@ def process_commandline(out: OutputBuffer, args: List[str], usage_cb: Callable[.
aconf.debug = True
out.debug = True
elif o in ('-g', '--gex-test'):
if not((any(re.search(regex_str, a) for regex_str in get_permitted_syntax_for_gex_test().values()))):
permitted_syntax = get_permitted_syntax_for_gex_test()
if not any(re.search(regex_str, a) for regex_str in permitted_syntax.values()):
usage_cb('{} {} is not valid'.format(o, a))
if re.search(permitted_syntax['RANGE'], a):
extracted_digits = re.findall(r'\d+', a)
bits_left_bound = int(extracted_digits[0])
bits_right_bound = int(extracted_digits[1])
bits_step = 1
if (len(extracted_digits)) == 3:
bits_step = int(extracted_digits[2])
if bits_step <= 0:
usage_cb('{} {} is not valid'.format(o, bits_step))
if all(x < 0 for x in (bits_left_bound, bits_right_bound)):
usage_cb('{} {} {} is not valid'.format(o, bits_left_bound, bits_right_bound))
aconf.gex_test = a
if len(args) == 0 and aconf.client_audit is False and aconf.target_file is None and aconf.list_policies is False and aconf.lookup == '' and aconf.manual is False:
usage_cb()
@ -928,8 +947,7 @@ def audit(out: OutputBuffer, aconf: AuditConf, sshv: Optional[int] = None, print
if aconf.client_audit is False:
HostKeyTest.run(out, s, kex)
if aconf.gex_test != '':
program_retval = invoke_modulus_size_test(out, s, kex, aconf)
return program_retval
return run_gex_granular_modulus_size_test(out, s, kex, aconf)
else:
GEXTest.run(out, s, kex)
@ -1079,15 +1097,11 @@ def get_permitted_syntax_for_gex_test() -> Dict[str, str]:
return syntax
def invoke_modulus_size_test(out: OutputBuffer, s: 'SSH_Socket', kex: 'SSH2_Kex', aconf: AuditConf) -> int:
def run_gex_granular_modulus_size_test(out: OutputBuffer, s: 'SSH_Socket', kex: 'SSH2_Kex', aconf: AuditConf) -> int:
'''Extracts the user specified modulus sizes and submits them for testing against the target server. Returns an exitcodes.* flag.'''
permitted_syntax = get_permitted_syntax_for_gex_test()
if not((any(re.search(regex_str, aconf.gex_test) for regex_str in permitted_syntax.values()))):
out.fail("Invalid syntax.")
return exitcodes.FAILURE
mod_dict: Dict[str, List[int]] = {}
# Range syntax.
@ -1096,18 +1110,9 @@ def invoke_modulus_size_test(out: OutputBuffer, s: 'SSH_Socket', kex: 'SSH2_Kex'
bits_left_bound = int(extracted_digits[0])
bits_right_bound = int(extracted_digits[1])
bits_step = 1
if (len(extracted_digits)) == 3:
bits_step = int(extracted_digits[2])
else:
bits_step = 1
if bits_step <= 0:
out.fail("Step value must be greater than zero.")
return exitcodes.FAILURE
if all(x < 0 for x in (bits_left_bound, bits_right_bound)):
out.fail("Start and end values cannot be negative.")
return exitcodes.FAILURE
# If the left value is greater than the right value, then the sequence
# operates from right to left.
@ -1119,7 +1124,7 @@ def invoke_modulus_size_test(out: OutputBuffer, s: 'SSH_Socket', kex: 'SSH2_Kex'
out.v("A separate test will be performed against each of the following modulus sizes: " + ", ".join([str(x) for x in bits_in_range_to_test]) + ".", write_now=True)
for i_bits in bits_in_range_to_test:
program_retval = GEXTest.modulus_size_test(out, s, kex, i_bits, i_bits, i_bits, mod_dict)
program_retval = GEXTest.granular_modulus_size_test(out, s, kex, i_bits, i_bits, i_bits, mod_dict)
if program_retval != exitcodes.GOOD:
return program_retval
@ -1128,15 +1133,16 @@ def invoke_modulus_size_test(out: OutputBuffer, s: 'SSH_Socket', kex: 'SSH2_Kex'
bits_in_list_to_test = aconf.gex_test.split(',')
out.v("A separate test will be performed against each of the following modulus sizes: " + ", ".join([str(x) for x in bits_in_list_to_test]) + ".", write_now=True)
for s_bits in bits_in_list_to_test:
program_retval = GEXTest.modulus_size_test(out, s, kex, int(s_bits), int(s_bits), int(s_bits), mod_dict)
program_retval = GEXTest.granular_modulus_size_test(out, s, kex, int(s_bits), int(s_bits), int(s_bits), mod_dict)
if program_retval != exitcodes.GOOD:
return program_retval
if re.search(permitted_syntax['LIST_WITH_MIN_PREF_MAX'], aconf.gex_test):
sets_of_min_pref_max = aconf.gex_test.split(',')
out.v("A separate test will be performed against each of the following sets of 'min:pref:max' modulus sizes: " + ', '.join(sets_of_min_pref_max), write_now=True)
for set_of_min_pref_max in sets_of_min_pref_max:
bits_in_list_to_test = set_of_min_pref_max.split(':')
program_retval = GEXTest.modulus_size_test(out, s, kex, int(bits_in_list_to_test[0]), int(bits_in_list_to_test[1]), int(bits_in_list_to_test[2]), mod_dict)
program_retval = GEXTest.granular_modulus_size_test(out, s, kex, int(bits_in_list_to_test[0]), int(bits_in_list_to_test[1]), int(bits_in_list_to_test[2]), mod_dict)
if program_retval != exitcodes.GOOD:
return program_retval
@ -1150,7 +1156,7 @@ def invoke_modulus_size_test(out: OutputBuffer, s: 'SSH_Socket', kex: 'SSH2_Kex'
for key, value in mod_dict.items():
padding = (max_key_len - len(key)) + 1
out.info(key + " " * padding + '--> ' + ', '.join(map(str, value)))
out.info(key + " " * padding + '--> ' + ', '.join([str(i) for i in value]))
return program_retval

23
ssh-audit.1
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@ -1,4 +1,4 @@
.TH SSH-AUDIT 1 "February 13, 2022"
.TH SSH-AUDIT 1 "March 13, 2022"
.SH NAME
\fBssh-audit\fP \- SSH server & client configuration auditor
.SH SYNOPSIS
@ -52,36 +52,29 @@ Starts a server on port 2222 to audit client software configuration. Use -p/--p
Enable debug output.
.TP
.B -g, \-\-gex-test=<n[,n,...] | min:pref:max[,min:pref:max,...] | n-n[:step]>
.B -g, \-\-gex-test=<x[,y,...] | min1:pref1:max1[,min2:pref2:max2,...] | x-y[:step]>
.br
Runs a Diffie-Hellman Group Exchange modulus size test against a server.
Diffie-Hellman requires the client and server to agree on a generator value and
a modulus value. In the "Group Exchange" implementation of Diffie-Hellman, the
client specifies the size of the modulus in bits by providing the server with
minimum, preferred and maximum values. The server then finds a group that best
matches the client's request, returning the corresponding generator and modulus.
For a full explanation of this process see RFC 4419 and its successors.
Diffie-Hellman requires the client and server to agree on a generator value and a modulus value. In the "Group Exchange" implementation of Diffie-Hellman, the client specifies the size of the modulus in bits by providing the server with minimum, preferred and maximum values. The server then finds a group that best matches the client's request, returning the corresponding generator and modulus. For a full explanation of this process see RFC 4419 and its successors.
This test acts as a client by providing an SSH server with the size of a modulus
and then obtains the size of the modulus returned by the server.
This test acts as a client by providing an SSH server with the size of a modulus and then obtains the size of the modulus returned by the server.
Three types of syntax are supported:
1. <n[,n,...]>
A comma delimited list of modulus sizes.
A test is performed against each value in the list where it acts as the minimum, preferred and maximum modulus size.
2. <min:pref:max[,min:pref:max,...]>
A set of three colon delimited values denoting minimum, preferred and maximum modulus size.
A test is performed against each set.
Multiple sets can specified as a comma separated list.
3. <n-n[:step]>
3. <x-y[:step]>
A range of modulus sizes with an optional step value. Step defaults to 1 if omitted.
If the left value is greater than the right value, then the sequence operates from right to left.
A test is performed against each value in the range where it acts as the minimum, preferred and maximum modulus size.