Ssl

與 Dovecot 的 IMAP 連接不斷失敗(超時)

  • March 16, 2018

*** TLDR ; 如果您遇到連接問題,不僅要確保已將所需的規則添加到防火牆,還要確保 ( $ iptables -L -v) 規則的順序正確!***


現在已經有幾天了,我無法弄清楚為什麼我的 IMAP 設置(在埠 993 上)拒絕工作(使用 Dovecot,版本 2.2.22)。連接不成功,由於某種原因我看不到。

使用 openssl 對連接進行故障排除:在埠 993 上連接不起作用:

$ openssl s_client -connect my-domain.com:993

返回:

connect: Connection timed out
connect:errno=110

但是使用的埠(993)似乎是開放的:

$ ufw status

返回:

Status: active

To                         Action      From
--                         ------      ----
22/tcp                     ALLOW       Anywhere                  
80/tcp                     ALLOW       Anywhere                  
443/tcp                    ALLOW       Anywhere                  
25/tcp                     ALLOW       Anywhere                  
587/tcp                    ALLOW       Anywhere                  
993/tcp                    ALLOW       Anywhere                  
143/tcp                    ALLOW       Anywhere                  
465/tcp                    ALLOW       Anywhere                  
110/tcp                    ALLOW       Anywhere                  
995/tcp                    ALLOW       Anywhere                  
22/tcp (v6)                ALLOW       Anywhere (v6)             
80/tcp (v6)                ALLOW       Anywhere (v6)             
443/tcp (v6)               ALLOW       Anywhere (v6)             
25/tcp (v6)                ALLOW       Anywhere (v6)             
587/tcp (v6)               ALLOW       Anywhere (v6)             
993/tcp (v6)               ALLOW       Anywhere (v6)             
143/tcp (v6)               ALLOW       Anywhere (v6)             
465/tcp (v6)               ALLOW       Anywhere (v6)             
110/tcp (v6)               ALLOW       Anywhere (v6)             
995/tcp (v6)               ALLOW       Anywhere (v6)            

我的鴿舍配置是:

$ dovecot -n

# 2.2.22 (fe789d2): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.13 (7b14904)
# OS: Linux 4.4.0-38-generic x86_64 Ubuntu 16.04.1 LTS ext4
auth_debug = yes
auth_debug_passwords = yes
auth_mechanisms = plain login
auth_verbose = yes
auth_verbose_passwords = sha1
mail_debug = yes
mail_location = maildir:/var/mail/vhosts/%d/%n
mail_privileged_group = mail
namespace inbox {
 inbox = yes
 location = 
 mailbox Drafts {
   special_use = \Drafts
 }
 mailbox Junk {
   special_use = \Junk
 }
 mailbox Sent {
   special_use = \Sent
 }
 mailbox "Sent Messages" {
   special_use = \Sent
 }
 mailbox Trash {
   special_use = \Trash
 }
 prefix = 
}
passdb {
 args = /etc/dovecot/dovecot-sql.conf.ext
 driver = sql
}
protocols = imap pop3 lmtp
service auth-worker {
 user = vmail
}
service auth {
 unix_listener /var/spool/postfix/private/auth {
   group = postfix
   mode = 0666
   user = postfix
 }
 unix_listener auth-userdb {
   mode = 0600
   user = vmail
 }
 user = dovecot
}
service imap-login {
 inet_listener imaps {
   port = 993
   ssl = yes
 }
}
service lmtp {
 unix_listener /var/spool/postfix/private/dovecot-lmtp {
   group = postfix
   mode = 0600
   user = postfix
 }
}
service pop3-login {
 inet_listener pop3s {
   port = 995
   ssl = yes
 }
}
ssl = required
ssl_cert = </etc/ssl/localcerts/www.my-domain.com.chained.crt
ssl_key = </etc/ssl/localcerts/www.my-domain.com.key
userdb {
 args = uid=vmail gid=vmail home=/var/mail/vhosts/%d/%n
 driver = static
}
verbose_ssl = yes

編輯1:

密鑰和證書確實匹配:

$ (openssl x509 -noout -modulus -in /etc/ssl/localcerts/www.my-domain.com.crt | openssl md5 ;\
openssl rsa -noout -modulus -in /etc/ssl/localcerts/www.my-domain.com.key | openssl md5) | uniq

僅返回 1 個標識符:

(stdin)= cfcbed2e4061910c47c5008d8732e522

編輯2:

啟用 Dovecot 的最大日誌記錄,其中:

auth_verbose=yes
auth_debug=yes
auth_debug_passwords=yes
mail_debug=yes
verbose_ssl=yes
auth_verbose_passwords=sha1

返回:

$ tail -f /var/log/mail.log

dovecot: master: Dovecot v2.2.22 (fe789d2) starting up for imap, pop3, lmtp (core dumps disabled)
[...]
dovecot: lmtp(5491): Connect from local
dovecot: lmtp(info@my-domain.com): +rg7LUpw6ldzFQAAxWOCog: msgid=<57ea704a99e89_b638aedb491d2@chbh.mail>: saved mail to INBOX
dovecot: lmtp(5491): Disconnect from local: Successful quit

編輯 3:

通過 SSL 連接到在埠 443 上使用相同證書和密鑰的網路伺服器(Nginx)完全可以正常工作:

$ openssl s_client -connect my-domain.com:443

編輯4:

我在舊伺服器上使用了相同版本的 Dovecot、相同的 Dovecot 配置和相同的證書+密鑰,其中與 Dovecot 的 IMAP 連接完全正常。

編輯 5:

嘗試openssl s_client使用參數在 IMAP 埠 993(通過)上建立連接-dtls1似乎做了一些事情:

$ openssl s_client -connect my-domain.com:993 -dtls1 -debug

返回(非常緩慢)這樣的東西:

CONNECTED(00000003)
write to 0x1425de0 [0x142f970] (202 bytes => 202 (0xCA))
0000 - 16 fe ff 00 00 00 00 00-00 00 00 00 bd 01 00 00   ................
0010 - b1 00 00 00 00 00 00 00-b1 fe ff 79 ab 6e 7d 25   ...........y.n}%
0020 - ac b9 bb 4b d9 4e 10 70-d4 fa 89 1b 72 bc 10 c1   ...K.N.p....r...
0030 - 46 30 c6 16 d8 46 63 4d-9f 75 9c 00 00 00 56 c0   F0...FcM.u....V.
[...]
0090 - 03 00 0a 00 ff 01 00 00-31 00 0b 00 04 03 00 01   ........1.......
00a0 - 02 00 0a 00 1c 00 1a 00-17 00 19 00 1c 00 1b 00   ................
00b0 - 18 00 1a 00 16 00 0e 00-0d 00 0b 00 0c 00 09 00   ................
00c0 - 0a 00 23 00 00 00 0f 00-01 01                     ..#.......
read from 0x1425de0 [0x142b413] (17741 bytes => -1 (0xFFFFFFFFFFFFFFFF))
write to 0x1425de0 [0x1434ed0] (202 bytes => 202 (0xCA))
0000 - 16 fe ff 00 00 00 00 00-00 00 01 00 bd 01 00 00   ................
0010 - b1 00 00 00 00 00 00 00-b1 fe ff 79 ab 6e 7d 25   ...........y.n}%
0020 - ac b9 bb 4b d9 4e 10 70-d4 fa 89 1b 72 bc 10 c1   ...K.N.p....r...
0030 - 46 30 c6 16 d8 46 63 4d-9f 75 9c 00 00 00 56 c0   F0...FcM.u....V.
[...]
00a0 - 02 00 0a 00 1c 00 1a 00-17 00 19 00 1c 00 1b 00   ................
00b0 - 18 00 1a 00 16 00 0e 00-0d 00 0b 00 0c 00 09 00   ................
00c0 - 0a 00 23 00 00 00 0f 00-01 01                     ..#.......
[...]
0070 - 45 00 44 00 43 00 42 c0-0e c0 04 00 2f 00 96 00   E.D.C.B...../...
0080 - 41 c0 12 c0 08 00 16 00-13 00 10 00 0d c0 0d c0   A...............
0090 - 03 00 0a 00 ff 01 00 00-31 00 0b 00 04 03 00 01   ........1.......
00a0 - 02 00 0a 00 1c 00 1a 00-17 00 19 00 1c 00 1b 00   ................
00b0 - 18 00 1a 00 16 00 0e 00-0d 00 0b 00 0c 00 09 00   ................
00c0 - 0a 00 23 00 00 00 0f 00-01 01                     ..#.......
read from 0x1e8dde0 [0x1e93413] (17741 bytes => -1 (0xFFFFFFFFFFFFFFFF))
139876009338520:error:1413C138:SSL routines:dtls1_check_timeout_num:read timeout expired:d1_lib.c:495:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 2424 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
   Protocol  : DTLSv1
   Cipher    : 0000
   Session-ID: 
   Session-ID-ctx: 
   Master-Key: 
   Key-Arg   : None
   PSK identity: None
   PSK identity hint: None
   SRP username: None
   Start Time: 1474892601
   Timeout   : 7200 (sec)
   Verify return code: 0 (ok)
---

…然後連接關閉。

但是,使用參數-tls1(TLSv1) 或-tls1_1(TLSv1.1) 或-tls1_2(TLSv1.2) 會返回超時消息:connect: Connection timed outconnect:errno=110

編輯 6:

如果我在 Dovecot 中啟用了安全 POP 埠 995,請重新啟動它,在防火牆中打開此埠,然後嘗試:

openssl s_client -connect my-domain.com:995

…我也收到超時錯誤connect: Connection timed outconnect:errno=110顯然表明問題的根源適用於 IMAPPOP。

編輯 7:

正確的程序似乎在正確的埠上偵聽:

$ netstat -tulpn

返回:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN      2597/master     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      2827/nginx      
tcp        0      0 127.0.0.1:8891          0.0.0.0:*               LISTEN      2327/opendkim   
tcp        0      0 127.0.0.1:2812          0.0.0.0:*               LISTEN      1918/monit      
tcp        0      0 127.0.0.1:34305         0.0.0.0:*               LISTEN      2915/public     
tcp        0      0 0.0.0.0:993             0.0.0.0:*               LISTEN      2306/dovecot    
tcp        0      0 0.0.0.0:995             0.0.0.0:*               LISTEN      2306/dovecot    
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      2269/mysqld     
tcp        0      0 0.0.0.0:587             0.0.0.0:*               LISTEN      2597/master     
tcp        0      0 0.0.0.0:110             0.0.0.0:*               LISTEN      2306/dovecot    
tcp        0      0 0.0.0.0:143             0.0.0.0:*               LISTEN      2306/dovecot    
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      2827/nginx      
tcp        0      0 0.0.0.0:465             0.0.0.0:*               LISTEN      2597/master     
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2249/sshd       
tcp6       0      0 :::25                   :::*                    LISTEN      2597/master     
tcp6       0      0 :::993                  :::*                    LISTEN      2306/dovecot    
tcp6       0      0 :::995                  :::*                    LISTEN      2306/dovecot    
tcp6       0      0 :::587                  :::*                    LISTEN      2597/master     
tcp6       0      0 :::110                  :::*                    LISTEN      2306/dovecot    
tcp6       0      0 :::143                  :::*                    LISTEN      2306/dovecot    
tcp6       0      0 :::465                  :::*                    LISTEN      2597/master   

編輯 8:

Telnet 僅適用於埠 80 和 443(由 Nginx 使用),所有其他埠似乎都沒有響應(超時)。

編輯 9:

我剛剛使用它進行了埠掃描nmap 12.34.56.78,它只顯示22/tcp | open | sshand80/tcp | open | http443/tcp | open | https。如果您查看ufw status上面發布的結果,您可以看到我允許了一個完整的埠列表,這些埠沒有被 nmap “找到”。造成這種情況的原因和解決方法是什麼?(我知道這不是我的網路或提供商——我可以連接到我的舊/“相同”伺服器,並且 nmap 掃描將所需的 IMAP 埠顯示為“打開”)。

編輯 10:

$ iptables -L -v

返回:

Chain INPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target     prot opt in     out     source               destination         
387K   57M f2b-HTTPS  tcp  --  any    any     anywhere             anywhere             tcp dpt:https
118K 7235K f2b-SSH    tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh
387K   57M f2b-HTTPS  tcp  --  any    any     anywhere             anywhere             tcp dpt:https
488K   64M f2b-nginx-http-auth  tcp  --  any    any     anywhere             anywhere             multiport dports http,https
118K 7228K f2b-sshd   tcp  --  any    any     anywhere             anywhere             multiport dports ssh
118K 7226K f2b-SSH    tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh
387K   57M f2b-HTTPS  tcp  --  any    any     anywhere             anywhere             tcp dpt:https
387K   57M f2b-HTTPS  tcp  --  any    any     anywhere             anywhere             tcp dpt:https
488K   64M f2b-nginx-http-auth  tcp  --  any    any     anywhere             anywhere             multiport dports http,https
118K 7226K f2b-sshd   tcp  --  any    any     anywhere             anywhere             multiport dports ssh
1381K  214M ACCEPT     all  --  lo     any     anywhere             anywhere            
222K   45M ACCEPT     all  --  any    any     anywhere             anywhere             ctstate RELATED,ESTABLISHED
 398 23248 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh
7903  443K ACCEPT     tcp  --  any    any     anywhere             anywhere             multiport dports http,https
7460  441K DROP       all  --  any    any     anywhere             anywhere            
   0     0 ufw-before-logging-input  all  --  any    any     anywhere             anywhere            
   0     0 ufw-before-input  all  --  any    any     anywhere             anywhere            
   0     0 ufw-after-input  all  --  any    any     anywhere             anywhere            
   0     0 ufw-after-logging-input  all  --  any    any     anywhere             anywhere            
   0     0 ufw-reject-input  all  --  any    any     anywhere             anywhere            
   0     0 ufw-track-input  all  --  any    any     anywhere             anywhere            

Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target     prot opt in     out     source               destination         
   0     0 ufw-before-logging-forward  all  --  any    any     anywhere             anywhere            
   0     0 ufw-before-forward  all  --  any    any     anywhere             anywhere            
   0     0 ufw-after-forward  all  --  any    any     anywhere             anywhere            
   0     0 ufw-after-logging-forward  all  --  any    any     anywhere             anywhere            
   0     0 ufw-reject-forward  all  --  any    any     anywhere             anywhere            
   0     0 ufw-track-forward  all  --  any    any     anywhere             anywhere            

Chain OUTPUT (policy ACCEPT 53 packets, 3160 bytes)
pkts bytes target     prot opt in     out     source               destination         
1575K  531M ufw-before-logging-output  all  --  any    any     anywhere             anywhere            
1575K  531M ufw-before-output  all  --  any    any     anywhere             anywhere            
 537 97799 ufw-after-output  all  --  any    any     anywhere             anywhere            
 537 97799 ufw-after-logging-output  all  --  any    any     anywhere             anywhere            
 537 97799 ufw-reject-output  all  --  any    any     anywhere             anywhere            
 537 97799 ufw-track-output  all  --  any    any     anywhere             anywhere            

Chain f2b-HTTPS (4 references)
pkts bytes target     prot opt in     out     source               destination         
1547K  228M RETURN     all  --  any    any     anywhere             anywhere            
   0     0 RETURN     all  --  any    any     anywhere             anywhere            
   0     0 RETURN     all  --  any    any     anywhere             anywhere            
   0     0 RETURN     all  --  any    any     anywhere             anywhere            

Chain f2b-SSH (2 references)
pkts bytes target     prot opt in     out     source               destination         
235K   14M RETURN     all  --  any    any     anywhere             anywhere            
   0     0 RETURN     all  --  any    any     anywhere             anywhere            

Chain f2b-nginx-http-auth (2 references)
pkts bytes target     prot opt in     out     source               destination         
975K  128M RETURN     all  --  any    any     anywhere             anywhere            
   0     0 RETURN     all  --  any    any     anywhere             anywhere            

Chain f2b-sshd (2 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 REJECT     all  --  any    any     62-210-106-228.rev.poneytelecom.eu  anywhere             reject-with icmp-port-unreachable
235K   14M RETURN     all  --  any    any     anywhere             anywhere            
   0     0 RETURN     all  --  any    any     anywhere             anywhere            

Chain ufw-after-forward (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-after-input (1 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 ufw-skip-to-policy-input  udp  --  any    any     anywhere             anywhere             udp dpt:netbios-ns
   0     0 ufw-skip-to-policy-input  udp  --  any    any     anywhere             anywhere             udp dpt:netbios-dgm
   0     0 ufw-skip-to-policy-input  tcp  --  any    any     anywhere             anywhere             tcp dpt:netbios-ssn
   0     0 ufw-skip-to-policy-input  tcp  --  any    any     anywhere             anywhere             tcp dpt:microsoft-ds
   0     0 ufw-skip-to-policy-input  udp  --  any    any     anywhere             anywhere             udp dpt:bootps
   0     0 ufw-skip-to-policy-input  udp  --  any    any     anywhere             anywhere             udp dpt:bootpc
   0     0 ufw-skip-to-policy-input  all  --  any    any     anywhere             anywhere             ADDRTYPE match dst-type BROADCAST

Chain ufw-after-logging-forward (1 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 LOG        all  --  any    any     anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-after-logging-input (1 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 LOG        all  --  any    any     anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-after-logging-output (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-after-output (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-before-forward (1 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 ACCEPT     all  --  any    any     anywhere             anywhere             ctstate RELATED,ESTABLISHED
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp destination-unreachable
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp source-quench
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp time-exceeded
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp parameter-problem
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp echo-request
   0     0 ufw-user-forward  all  --  any    any     anywhere             anywhere            

Chain ufw-before-input (1 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 ACCEPT     all  --  lo     any     anywhere             anywhere            
   0     0 ACCEPT     all  --  any    any     anywhere             anywhere             ctstate RELATED,ESTABLISHED
   0     0 ufw-logging-deny  all  --  any    any     anywhere             anywhere             ctstate INVALID
   0     0 DROP       all  --  any    any     anywhere             anywhere             ctstate INVALID
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp destination-unreachable
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp source-quench
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp time-exceeded
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp parameter-problem
   0     0 ACCEPT     icmp --  any    any     anywhere             anywhere             icmp echo-request
   0     0 ACCEPT     udp  --  any    any     anywhere             anywhere             udp spt:bootps dpt:bootpc
   0     0 ufw-not-local  all  --  any    any     anywhere             anywhere            
   0     0 ACCEPT     udp  --  any    any     anywhere             224.0.0.251          udp dpt:mdns
   0     0 ACCEPT     udp  --  any    any     anywhere             239.255.255.250      udp dpt:1900
   0     0 ufw-user-input  all  --  any    any     anywhere             anywhere            

Chain ufw-before-logging-forward (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-before-logging-input (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-before-logging-output (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-before-output (1 references)
pkts bytes target     prot opt in     out     source               destination         
1381K  214M ACCEPT     all  --  any    lo      anywhere             anywhere            
194K  317M ACCEPT     all  --  any    any     anywhere             anywhere             ctstate RELATED,ESTABLISHED
 537 97799 ufw-user-output  all  --  any    any     anywhere             anywhere            

Chain ufw-logging-allow (0 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 LOG        all  --  any    any     anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW ALLOW] "

Chain ufw-logging-deny (2 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 RETURN     all  --  any    any     anywhere             anywhere             ctstate INVALID limit: avg 3/min burst 10
   0     0 LOG        all  --  any    any     anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-not-local (1 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 RETURN     all  --  any    any     anywhere             anywhere             ADDRTYPE match dst-type LOCAL
   0     0 RETURN     all  --  any    any     anywhere             anywhere             ADDRTYPE match dst-type MULTICAST
   0     0 RETURN     all  --  any    any     anywhere             anywhere             ADDRTYPE match dst-type BROADCAST
   0     0 ufw-logging-deny  all  --  any    any     anywhere             anywhere             limit: avg 3/min burst 10
   0     0 DROP       all  --  any    any     anywhere             anywhere            

Chain ufw-reject-forward (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-reject-input (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-reject-output (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-skip-to-policy-forward (0 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 DROP       all  --  any    any     anywhere             anywhere            

Chain ufw-skip-to-policy-input (7 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 DROP       all  --  any    any     anywhere             anywhere            

Chain ufw-skip-to-policy-output (0 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 ACCEPT     all  --  any    any     anywhere             anywhere            

Chain ufw-track-forward (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-track-input (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-track-output (1 references)
pkts bytes target     prot opt in     out     source               destination         
 112 10791 ACCEPT     tcp  --  any    any     anywhere             anywhere             ctstate NEW
 300 22604 ACCEPT     udp  --  any    any     anywhere             anywhere             ctstate NEW

Chain ufw-user-forward (1 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-user-input (1 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh
   0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:http
   0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:https
   0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:smtp
   0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:submission
   0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:imaps

Chain ufw-user-limit (0 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 LOG        all  --  any    any     anywhere             anywhere             limit: avg 3/min burst 5 LOG level warning prefix "[UFW LIMIT BLOCK] "
   0     0 REJECT     all  --  any    any     anywhere             anywhere             reject-with icmp-port-unreachable

Chain ufw-user-limit-accept (0 references)
pkts bytes target     prot opt in     out     source               destination         
   0     0 ACCEPT     all  --  any    any     anywhere             anywhere            

Chain ufw-user-logging-forward (0 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-user-logging-input (0 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-user-logging-output (0 references)
pkts bytes target     prot opt in     out     source               destination         

Chain ufw-user-output (1 references)
pkts bytes target     prot opt in     out     source               destination   

ufw您在拒絕imaps連接的規則之前有一個 DROP 規則。這不是唯一會產生問題的規則。您應該檢查他們是如何到達那裡的,也許您使用-I的是-Ainbefore.rulesafter.rules

1381K  214M ACCEPT     all  --  lo     any     anywhere             anywhere            
222K   45M ACCEPT     all  --  any    any     anywhere             anywhere             ctstate RELATED,ESTABLISHED
 398 23248 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh
7903  443K ACCEPT     tcp  --  any    any     anywhere             anywhere             multiport dports http,https
7460  441K DROP       all  --  any    any     anywhere             anywhere 

以上所有規則都插入在ufw規則之前,可能會產生問題。例如,如果您配置ufw為拒絕 http 或 https,則這些規則無論如何都會允許這些埠。

引用自:https://serverfault.com/questions/804443