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Merge pull request #2014 from sebres/sshd-fix-connects-with-mult-pub-keys 

stop ban of legitimate users with multiple public keys (e. g. git, etc)
pull/2019/merge
Serg G. Brester 2018-01-11 10:27:35 +01:00 committed by GitHub
parent c36fbdf743 1c0fc73e48
commit 6251fcf5f7
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 35 additions and 7 deletions
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8
ChangeLog
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@ -50,9 +50,11 @@ ver. 0.10.2-dev-1 (2017/??/??) - development edition
- fixed syntax error in achnor definition (documentation, see gh-1919);
- enclose ports in braces for multiport jails (see gh-1925);
* `action.d/firewallcmd-ipset.conf`: fixed create of set for ipv6 (missing `family inet6`, gh-1990)
* `filter.d/sshd.conf`: extended failregex for modes "extra"/"aggressive": now finds all possible (also future)
forms of "no matching (cipher|mac|MAC|compression method|key exchange method|host key type) found",
see "ssherr.c" for all possible SSH_ERR_..._ALG_MATCH errors (gh-1943, gh-1944);
* `filter.d/sshd.conf`:
- extended failregex for modes "extra"/"aggressive": now finds all possible (also future)
forms of "no matching (cipher|mac|MAC|compression method|key exchange method|host key type) found",
see "ssherr.c" for all possible SSH_ERR_..._ALG_MATCH errors (gh-1943, gh-1944);
- fixed failregex in order to avoid banning of legitimate users with multiple public keys (gh-2014, gh-1263);
### New Features
* datedetector: extended default date-patterns (allows extra space between the date and time stamps);

4
config/filter.d/sshd.conf
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@ -34,7 +34,8 @@ prefregex = ^<F-MLFID>%(__prefix_line)s</F-MLFID>%(__pref)s<F-CONTENT>.+</F-CONT
cmnfailre = ^[aA]uthentication (?:failure|error|failed) for <F-USER>.*</F-USER> from <HOST>( via \S+)?\s*%(__suff)s$
^User not known to the underlying authentication module for <F-USER>.*</F-USER> from <HOST>\s*%(__suff)s$
^Failed \S+ for (?P<cond_inv>invalid user )?<F-USER>(?P<cond_user>\S+)|(?(cond_inv)(?:(?! from ).)*?|[^:]+)</F-USER> from <HOST>%(__on_port_opt)s(?: ssh\d*)?(?(cond_user): |(?:(?:(?! from ).)*)$)
^Failed \S+ for invalid user <F-USER>(?P<cond_user>\S+)|(?:(?! from ).)*?</F-USER> from <HOST>%(__on_port_opt)s(?: ssh\d*)?(?(cond_user): |(?:(?:(?! from ).)*)$)
^Failed \b(?!publickey)\S+ for (?P<cond_inv>invalid user )?<F-USER>(?P<cond_user>\S+)|(?(cond_inv)(?:(?! from ).)*?|[^:]+)</F-USER> from <HOST>%(__on_port_opt)s(?: ssh\d*)?(?(cond_user): |(?:(?:(?! from ).)*)$)
^<F-USER>ROOT</F-USER> LOGIN REFUSED.* FROM <HOST>\s*%(__suff)s$
^[iI](?:llegal|nvalid) user <F-USER>.*?</F-USER> from <HOST>%(__on_port_opt)s\s*$
^User <F-USER>.+</F-USER> from <HOST> not allowed because not listed in AllowUsers\s*%(__suff)s$
@ -50,6 +51,7 @@ cmnfailre = ^[aA]uthentication (?:failure|error|failed) for <F-USER>.*</F-USER>
^<F-MLFFORGET>Disconnecting</F-MLFFORGET>: Too many authentication failures(?: for <F-USER>.+?</F-USER>)?%(__suff)s
^<F-NOFAIL>Received <F-MLFFORGET>disconnect</F-MLFFORGET></F-NOFAIL> from <HOST>: 11:
^<F-NOFAIL>Connection <F-MLFFORGET>closed</F-MLFFORGET></F-NOFAIL> by <HOST>%(__suff)s$
^<F-MLFFORGET><F-NOFAIL>Accepted publickey</F-NOFAIL></F-MLFFORGET> for \S+ from <HOST>(?:\s|$)
mdre-normal =

3
fail2ban/tests/config/filter.d/zzz-sshd-obsolete-multiline.conf
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@ -31,7 +31,8 @@ __alg_match = (?:(?:\w+ (?!found\b)){0,2}\w+)
cmnfailre = ^%(__prefix_line_sl)s[aA]uthentication (?:failure|error|failed) for .* from <HOST>( via \S+)?\s*%(__suff)s$
^%(__prefix_line_sl)sUser not known to the underlying authentication module for .* from <HOST>\s*%(__suff)s$
^%(__prefix_line_sl)sFailed \S+ for (?P<cond_inv>invalid user )?(?P<user>(?P<cond_user>\S+)|(?(cond_inv)(?:(?! from ).)*?|[^:]+)) from <HOST>%(__on_port_opt)s(?: ssh\d*)?(?(cond_user): |(?:(?:(?! from ).)*)$)
^%(__prefix_line_sl)sFailed \S+ for invalid user <F-USER>(?P<cond_user>\S+)|(?:(?! from ).)*?</F-USER> from <HOST>%(__on_port_opt)s(?: ssh\d*)?(?(cond_user): |(?:(?:(?! from ).)*)$)
^%(__prefix_line_sl)sFailed \b(?!publickey)\S+ for (?P<cond_inv>invalid user )?<F-USER>(?P<cond_user>\S+)|(?(cond_inv)(?:(?! from ).)*?|[^:]+)</F-USER> from <HOST>%(__on_port_opt)s(?: ssh\d*)?(?(cond_user): |(?:(?:(?! from ).)*)$)
^%(__prefix_line_sl)sROOT LOGIN REFUSED.* FROM <HOST>\s*%(__suff)s$
^%(__prefix_line_sl)s[iI](?:llegal|nvalid) user .*? from <HOST>%(__on_port_opt)s\s*$
^%(__prefix_line_sl)sUser .+ from <HOST> not allowed because not listed in AllowUsers\s*%(__suff)s$

27
fail2ban/tests/files/logs/sshd
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@ -141,10 +141,33 @@ Nov 11 08:04:52 redbamboo sshd[2737]: Failed password for invalid user test from
# failJSON: { "time": "2004-11-11T08:04:52", "match": true , "host": "127.0.0.1", "desc": "More complex injecting on auth-info ssh test@localhost, auth-info: ' from 10.10.1.2 port 55555 ssh2'" }
Nov 11 08:04:52 redbamboo sshd[2737]: Failed password for invalid user test from 127.0.0.1 port 58946 ssh2: from 10.10.1.2 port 55555 ssh2
# Failure on connect of invalid user with public keys:
# failJSON: { "time": "2005-07-05T18:22:44", "match": true , "host": "127.0.0.1", "desc": "Failed publickey for ..." }
Jul 05 18:22:44 mercury sshd[4669]: Failed publickey for graysky from 127.0.0.1 port 37954 ssh2: RSA SHA256:v3dpapGleDaUKf$4V1vKyR9ZyUgjaJAmoCTcb2PLljI
Jul 05 18:22:44 mercury sshd[4669]: Failed publickey for invalid user graysky from 127.0.0.1 port 37954 ssh2: RSA SHA256:v3dpapGleDaUKf$4V1vKyR9ZyUgjaJAmoCTcb2PLljI
# failJSON: { "time": "2005-07-05T18:22:45", "match": true , "host": "aaaa:bbbb:cccc:1234::1:1", "desc": "Failed publickey for ..." }
Jul 05 18:22:45 mercury sshd[4670]: Failed publickey for graysky from aaaa:bbbb:cccc:1234::1:1 port 37955 ssh2: RSA SHA256:v3dpapGleDaUKf$4V1vKyR9ZyUgjaJAmoCTcb2PLljI
Jul 05 18:22:45 mercury sshd[4670]: Failed publickey for invalid user graysky from aaaa:bbbb:cccc:1234::1:1 port 37955 ssh2: RSA SHA256:v3dpapGleDaUKf$4V1vKyR9ZyUgjaJAmoCTcb2PLljI
# Ignore tries of legitimate users with multiple public keys (gh-1263):
# failJSON: { "match": false }
Nov 28 09:16:03 srv sshd[32307]: Failed publickey for git from 192.0.2.1 port 57904 ssh2: ECDSA 0e:ff:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
# failJSON: { "match": false }
Nov 28 09:16:03 srv sshd[32307]: Failed publickey for git from 192.0.2.1 port 57904 ssh2: RSA 04:bc:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
# failJSON: { "match": false }
Nov 28 09:16:03 srv sshd[32307]: Postponed publickey for git from 192.0.2.1 port 57904 ssh2 [preauth]
# failJSON: { "match": false }
Nov 28 09:16:03 srv sshd[32307]: Accepted publickey for git from 192.0.2.1 port 57904 ssh2: DSA 36:48:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
# failJSON: { "match": false, "desc": "Should be forgotten by success/accepted public key" }
Nov 28 09:16:03 srv sshd[32307]: Connection closed by 192.0.2.1 [preauth]
# Failure on connect with valid user-name but wrong public keys (retarded to disconnect/too many errors, because of gh-1263):
# failJSON: { "match": false }
Nov 28 09:16:05 srv sshd[32310]: Failed publickey for git from 192.0.2.111 port 57910 ssh2: ECDSA 1e:fe:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
# failJSON: { "match": false }
Nov 28 09:16:05 srv sshd[32310]: Failed publickey for git from 192.0.2.111 port 57910 ssh2: RSA 14:ba:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
# failJSON: { "match": false }
Nov 28 09:16:05 srv sshd[32310]: Disconnecting: Too many authentication failures for git [preauth]
# failJSON: { "time": "2004-11-28T09:16:05", "match": true , "host": "192.0.2.111", "desc": "Should catch failure - no success/no accepted public key" }
Nov 28 09:16:05 srv sshd[32310]: Connection closed by 192.0.2.111 [preauth]
# failJSON: { "match": false }
Nov 23 21:50:19 sshd[8148]: Disconnecting: Too many authentication failures for root [preauth]