Hi,

After reading more information on this kind of error I captured a few transactions with Wireshark running on the raspberry pi hosting squid 4.6 and opensll 1.1.1d. I captured some transactions when trying to access ebay.fr which is currently not successful with the setup I have with the error of inappropriate fallback mentioned below.

I am not familiar with TLS transactions so I will try to present a high level view of the transactions between the raspberry pi and the ebay.fr server. I hope you can guide me as to what I should focus on to understand, if possible, the issue I have.

A bird's eye view of the transactions from Wireshark over time is :

     23 0.175795327    192.168.1.32 192.168.1.1           DNS      71     Standard query 0x057e A www.ebay.fr      24 0.214678299    192.168.1.1           192.168.1.32 DNS      165    Standard query response 0x057e A www.ebay.fr CNAME slot11847.ebay.com.edgekey.net CNAME e11847.g.akamaiedge.net A 23.57.6.166      25 0.301067317    192.168.1.32          23.57.6.166 TCP      74     53934 → 443 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=365186690 TSecr=0 WS=128      26 0.302488046    192.168.1.32          23.57.6.166 TCP      74     53936 → 443 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=365186691 TSecr=0 WS=128      27 0.328959454    23.57.6.166           192.168.1.32 TCP      74     443 → 53934 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3470404062 TSecr=365186690 WS=128      28 0.329115340    192.168.1.32          23.57.6.166 TCP      66     53934 → 443 [ACK] Seq=1 Ack=1 Win=64256 Len=0 TSval=365186718 TSecr=3470404062      29 0.329752684    192.168.1.32          23.57.6.166 TLSv1.2  583    Client Hello      30 0.330530288    23.57.6.166           192.168.1.32 TCP      74     443 → 53936 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3470404064 TSecr=365186691 WS=128      31 0.330644819    192.168.1.32          23.57.6.166 TCP      66     53936 → 443 [ACK] Seq=1 Ack=1 Win=64256 Len=0 TSval=365186719 TSecr=3470404064      32 0.331192579    192.168.1.32          23.57.6.166 TLSv1.2  583    Client Hello      35 0.351054404    192.168.1.32          192.168.1.98 TCP      54     5900 → 49903 [ACK] Seq=14256 Ack=97 Win=501 Len=0      36 0.363323884    23.57.6.166           192.168.1.32 TCP      66     443 → 53934 [ACK] Seq=1 Ack=518 Win=64768 Len=0 TSval=3470404096 TSecr=365186719      37 0.364291801    23.57.6.166           192.168.1.32 TLSv1.2  1514   Server Hello      38 0.364347270    192.168.1.32          23.57.6.166 TCP      66     53934 → 443 [ACK] Seq=518 Ack=1449 Win=64128 Len=0 TSval=365186753 TSecr=3470404096      39 0.365482999    23.57.6.166           192.168.1.32 TCP      1514   443 → 53934 [PSH, ACK] Seq=1449 Ack=518 Win=64768 Len=1448 TSval=3470404096 TSecr=365186719 [TCP segment of a reassembled PDU]      40 0.365535030    192.168.1.32          23.57.6.166 TCP      66     53934 → 443 [ACK] Seq=518 Ack=2897 Win=64128 Len=0 TSval=365186754 TSecr=3470404096      41 0.366217999    23.57.6.166           192.168.1.32 TCP      1266   443 → 53934 [PSH, ACK] Seq=2897 Ack=518 Win=64768 Len=1200 TSval=3470404096 TSecr=365186719 [TCP segment of a reassembled PDU]      42 0.366279041    192.168.1.32          23.57.6.166 TCP      66     53934 → 443 [ACK] Seq=518 Ack=4097 Win=64128 Len=0 TSval=365186755 TSecr=3470404096      43 0.366321697    23.57.6.166           192.168.1.32 TCP      74     [TCP Retransmission] 443 → 53936 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3470404096 TSecr=365186691 WS=128      44 0.366410135    192.168.1.32          23.57.6.166 TCP      66     [TCP Dup ACK 31#1] 53936 → 443 [ACK] Seq=518 Ack=1 Win=64256 Len=0 TSval=365186755 TSecr=3470404064      45 0.366709770    23.57.6.166           192.168.1.32 TLSv1.2  991    Certificate, Certificate Status, Server Key Exchange, Server Hello Done      46 0.366754978    192.168.1.32          23.57.6.166 TCP      66     53934 → 443 [ACK] Seq=518 Ack=5022 Win=64128 Len=0 TSval=365186756 TSecr=3470404097      47 0.369138676    23.57.6.166           192.168.1.32 TCP      66     443 → 53936 [ACK] Seq=1 Ack=518 Win=64768 Len=0 TSval=3470404102 TSecr=365186720      48 0.370432739    23.57.6.166           192.168.1.32 TLSv1.2  1514   Server Hello      49 0.370506906    192.168.1.32          23.57.6.166 TCP      66     53936 → 443 [ACK] Seq=518 Ack=1449 Win=64128 Len=0 TSval=365186759 TSecr=3470404102      50 0.371401125    23.57.6.166           192.168.1.32 TCP      1514   443 → 53936 [PSH, ACK] Seq=1449 Ack=518 Win=64768 Len=1448 TSval=3470404102 TSecr=365186720 [TCP segment of a reassembled PDU]      51 0.371449250    192.168.1.32          23.57.6.166 TCP      66     53936 → 443 [ACK] Seq=518 Ack=2897 Win=64128 Len=0 TSval=365186760 TSecr=3470404102      52 0.372385968    23.57.6.166           192.168.1.32 TCP      1266   443 → 53936 [PSH, ACK] Seq=2897 Ack=518 Win=64768 Len=1200 TSval=3470404102 TSecr=365186720 [TCP segment of a reassembled PDU]      53 0.372438156    192.168.1.32          23.57.6.166 TCP      66     53936 → 443 [ACK] Seq=518 Ack=4097 Win=64128 Len=0 TSval=365186761 TSecr=3470404102      54 0.372859562    23.57.6.166           192.168.1.32 TLSv1.2  991    Certificate, Certificate Status, Server Key Exchange, Server Hello Done      55 0.372905395    192.168.1.32          23.57.6.166 TCP      66     53936 → 443 [ACK] Seq=518 Ack=5022 Win=64128 Len=0 TSval=365186762 TSecr=3470404103      56 0.374064614    192.168.1.32          23.57.6.166 TCP      66     53934 → 443 [FIN, ACK] Seq=518 Ack=5022 Win=64128 Len=0 TSval=365186763 TSecr=3470404097      57 0.382856646    192.168.1.32          23.57.6.166 TCP      66     53936 → 443 [FIN, ACK] Seq=518 Ack=5022 Win=64128 Len=0 TSval=365186772 TSecr=3470404103      58 0.387044251    192.168.1.32          23.57.6.166 TCP      74     53938 → 443 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=365186776 TSecr=0 WS=128      59 0.401877325    192.168.1.32          23.57.6.166 TCP      74     53940 → 443 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=365186791 TSecr=0 WS=128      60 0.402472117    23.57.6.166           192.168.1.32 TCP      66     443 → 53934 [FIN, ACK] Seq=5022 Ack=519 Win=64768 Len=0 TSval=3470404136 TSecr=365186763      61 0.402574981    192.168.1.32          23.57.6.166 TCP      66     53934 → 443 [ACK] Seq=519 Ack=5023 Win=64128 Len=0 TSval=365186791 TSecr=3470404136      62 0.410122326    23.57.6.166           192.168.1.32 TCP      66     443 → 53936 [FIN, ACK] Seq=5022 Ack=519 Win=64768 Len=0 TSval=3470404143 TSecr=365186772      63 0.410185971    192.168.1.32          23.57.6.166 TCP      66     53936 → 443 [ACK] Seq=519 Ack=5023 Win=64128 Len=0 TSval=365186799 TSecr=3470404143      64 0.415533941    23.57.6.166           192.168.1.32 TCP      74     443 → 53938 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3470404148 TSecr=365186776 WS=128      65 0.415615607    192.168.1.32          23.57.6.166 TCP      66     53938 → 443 [ACK] Seq=1 Ack=1 Win=64256 Len=0 TSval=365186804 TSecr=3470404148      66 0.416199514    192.168.1.32          23.57.6.166 TLSv1.2  583    Client Hello      67 0.429629098    23.57.6.166           192.168.1.32 TCP      74     443 → 53940 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3470404163 TSecr=365186791 WS=128      68 0.429722796    192.168.1.32          23.57.6.166 TCP      66     53940 → 443 [ACK] Seq=1 Ack=1 Win=64256 Len=0 TSval=365186819 TSecr=3470404163      69 0.430195036    192.168.1.32          23.57.6.166 TLSv1.2  583    Client Hello      70 0.449937225    23.57.6.166           192.168.1.32 TCP      66     443 → 53938 [ACK] Seq=1 Ack=518 Win=64768 Len=0 TSval=3470404182 TSecr=365186805      71 0.451000037    23.57.6.166           192.168.1.32 TLSv1.2  1514   Server Hello      72 0.451064100    192.168.1.32          23.57.6.166 TCP      66     53938 → 443 [ACK] Seq=518 Ack=1449 Win=64128 Len=0 TSval=365186840 TSecr=3470404183      73 0.451980194    23.57.6.166           192.168.1.32 TCP      1514   443 → 53938 [PSH, ACK] Seq=1449 Ack=518 Win=64768 Len=1448 TSval=3470404183 TSecr=365186805 [TCP segment of a reassembled PDU]      74 0.452031756    192.168.1.32          23.57.6.166 TCP      66     53938 → 443 [ACK] Seq=518 Ack=2897 Win=64128 Len=0 TSval=365186841 TSecr=3470404183      75 0.452935767    23.57.6.166           192.168.1.32 TCP      1266   443 → 53938 [PSH, ACK] Seq=2897 Ack=518 Win=64768 Len=1200 TSval=3470404183 TSecr=365186805 [TCP segment of a reassembled PDU]      76 0.452991027    192.168.1.32          23.57.6.166 TCP      66     53938 → 443 [ACK] Seq=518 Ack=4097 Win=64128 Len=0 TSval=365186842 TSecr=3470404183      77 0.453443475    23.57.6.166           192.168.1.32 TLSv1.2  991    Certificate, Certificate Status, Server Key Exchange, Server Hello Done      78 0.453498215    192.168.1.32          23.57.6.166 TCP      66     53938 → 443 [ACK] Seq=518 Ack=5022 Win=64128 Len=0 TSval=365186842 TSecr=3470404184      79 0.461625715    192.168.1.32          23.57.6.166 TCP      66     53938 → 443 [FIN, ACK] Seq=518 Ack=5022 Win=64128 Len=0 TSval=365186850 TSecr=3470404184      80 0.463463320    23.57.6.166           192.168.1.32 TCP      66     443 → 53940 [ACK] Seq=1 Ack=518 Win=64768 Len=0 TSval=3470404196 TSecr=365186819      81 0.464344413    23.57.6.166           192.168.1.32 TLSv1.2  1514   Server Hello      82 0.464433476    192.168.1.32          23.57.6.166 TCP      66     53940 → 443 [ACK] Seq=518 Ack=1449 Win=64128 Len=0 TSval=365186853 TSecr=3470404197      83 0.465538632    23.57.6.166           192.168.1.32 TCP      1514   443 → 53940 [PSH, ACK] Seq=1449 Ack=518 Win=64768 Len=1448 TSval=3470404197 TSecr=365186819 [TCP segment of a reassembled PDU]      84 0.465628789    192.168.1.32          23.57.6.166 TCP      66     53940 → 443 [ACK] Seq=518 Ack=2897 Win=64128 Len=0 TSval=365186854 TSecr=3470404197      85 0.466298945    23.57.6.166           192.168.1.32 TCP      1266   443 → 53940 [PSH, ACK] Seq=2897 Ack=518 Win=64768 Len=1200 TSval=3470404197 TSecr=365186819 [TCP segment of a reassembled PDU]      86 0.466437851    192.168.1.32          23.57.6.166 TCP      66     53940 → 443 [ACK] Seq=518 Ack=4097 Win=64128 Len=0 TSval=365186855 TSecr=3470404197      87 0.467042591    23.57.6.166           192.168.1.32 TLSv1.2  991    Certificate, Certificate Status, Server Key Exchange, Server Hello Done      88 0.467190976    192.168.1.32          23.57.6.166 TCP      66     53940 → 443 [ACK] Seq=518 Ack=5022 Win=64128 Len=0 TSval=365186856 TSecr=3470404197

I start my description with a Client Hello step from the raspberry pi to the ebay.fr server :

   No.     Time           Source Destination           Protocol Length Info
         29 0.329752684    192.168.1.32 23.57.6.166           TLSv1.2 
   583    Client Hello

   ...

   Transport Layer Security
        TLSv1.2 Record Layer: Handshake Protocol: Client Hello
            Content Type: Handshake (22)
            Version: TLS 1.0 (0x0301)
            Length: 512
            Handshake Protocol: Client Hello
                Handshake Type: Client Hello (1)
                Length: 508
                Version: TLS 1.2 (0x0303)

Then, there is another Client Hello step which seems quite similar to the previous one :

   No.     Time           Source Destination           Protocol Length Info
         32 0.331192579    192.168.1.32 23.57.6.166           TLSv1.2 
   583    Client Hello

   ...

   Transport Layer Security
        TLSv1.2 Record Layer: Handshake Protocol: Client Hello
            Content Type: Handshake (22)
            Version: TLS 1.0 (0x0301)
            Length: 512
            Handshake Protocol: Client Hello
                Handshake Type: Client Hello (1)
                Length: 508
                Version: TLS 1.2 (0x0303)

Then a Server Hello :

   No.     Time           Source Destination           Protocol Length Info
         37 0.364291801    23.57.6.166 192.168.1.32          TLSv1.2 
   1514   Server Hello

   ...

   Transport Layer Security
        TLSv1.2 Record Layer: Handshake Protocol: Server Hello
            Content Type: Handshake (22)
            Version: TLS 1.2 (0x0303)
            Length: 78
            Handshake Protocol: Server Hello
                Handshake Type: Server Hello (2)
                Length: 74
                Version: TLS 1.2 (0x0303)

                Random:
   08f25b54bfe62d98736a4e5e8cc5a3f4ab97c040c1a892a26110e4d704b2fd9e
                    GMT Unix Time: Oct  4, 1974 08:40:20.000000000
   Paris, Madrid (heure d’été)
                    Random Bytes:
   bfe62d98736a4e5e8cc5a3f4ab97c040c1a892a26110e4d704b2fd9e
                Session ID Length: 0
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
   (0xc02f)

   ...

So it seems the server found a common cipher with the client. I am not sure then what to look for. Frames 43 and 44 are detected by Wireshark as retransmissions but I am not sure it is a problem.

I noticed frame 45 which is about the Certificate, Certificate Status, Server Key Exchange and Server Hello Done

   No.     Time           Source Destination           Protocol Length Info
         45 0.366709770    23.57.6.166 192.168.1.32          TLSv1.2 
   991    Certificate, Certificate Status, Server Key Exchange, Server
   Hello Done

   Transport Layer Security
        TLSv1.2 Record Layer: Handshake Protocol: Certificate
            Content Type: Handshake (22)
            Version: TLS 1.2 (0x0303)
            Length: 4102
            Handshake Protocol: Certificate
                Handshake Type: Certificate (11)
         ...
   Transport Layer Security
        TLSv1.2 Record Layer: Handshake Protocol: Certificate Status
            Content Type: Handshake (22)
            Version: TLS 1.2 (0x0303)
            Length: 479
            Handshake Protocol: Certificate Status
                Handshake Type: Certificate Status (22)
                Length: 475
                Certificate Status Type: OCSP (1)
                OCSP Response Length: 471
                OCSP Response
   ...
        TLSv1.2 Record Layer: Handshake Protocol: Server Key Exchange
            Content Type: Handshake (22)
            Version: TLS 1.2 (0x0303)
            Length: 333
            Handshake Protocol: Server Key Exchange
                Handshake Type: Server Key Exchange (12)
                Length: 329
                EC Diffie-Hellman Server Params
   ...
        TLSv1.2 Record Layer: Handshake Protocol: Server Hello Done
            Content Type: Handshake (22)
            Version: TLS 1.2 (0x0303)
            Length: 4
            Handshake Protocol: Server Hello Done
                Handshake Type: Server Hello Done (14)
                Length: 0

   ...

I noticed there is a mention of Diffie-Hellman which may require some attention but I am not sure.

I am sorry for all this information but I really look forward to knowing more and managing to sort this issue out. Is there anything in this information that is relevant to understanding the issue I have ? Where should I focus ?

Best regards,

JF

Le 02/01/2021 à 11:26, jean francois hasson a écrit :

Hi,

Thank you Amos Jeffries and Antony Stone. It seems the configuration I have provides the functionality of filtering I am looking for.

There is a strange behavior I can see when accessing some legitimate sites which I see traces of in cache.log :

    2021/01/02 10:55:48 kid1| helperOpenServers: Starting 1/20
    'squidGuard' processes
    2021/01/02 10:57:31 kid1| ERROR: negotiating TLS on FD 39:
    error:1407743E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert
    inappropriate fallback (1/-1/0)
    2021/01/02 10:57:31 kid1| Error negotiating SSL connection on FD
    38: error:00000001:lib(0):func(0):reason(1) (1/-1)
    2021/01/02 10:57:32 kid1| ERROR: negotiating TLS on FD 38:
    error:1407743E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert
    inappropriate fallback (1/-1/0)
    2021/01/02 10:57:32 kid1| Error negotiating SSL connection on FD
    35: error:00000001:lib(0):func(0):reason(1) (1/-1)
    2021/01/02 10:57:40 kid1| Starting new redirector helpers...
    2021/01/02 10:57:40 kid1| helperOpenServers: Starting 1/20
    'squidGuard' processes
    2021/01/02 10:58:09 kid1| ERROR: negotiating TLS on FD 51:
    error:1407743E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert
    inappropriate fallback (1/-1/0)
    2021/01/02 10:58:09 kid1| Error negotiating SSL connection on FD
    40: error:00000001:lib(0):func(0):reason(1) (1/-1)
    2021/01/02 10:58:10 kid1| ERROR: negotiating TLS on FD 51:
    error:1407743E:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert
    inappropriate fallback (1/-1/0)
    2021/01/02 10:58:10 kid1| Error negotiating SSL connection on FD
    40: error:00000001:lib(0):func(0):reason(1) (1/-1)

I noticed other users of squid encountered similar issues but I did not find a clear answer to the issue. Is there a problem with my setup ? I am not sure to be able to solve it on my own ! Any help would be appreciated.

Best regards,

JF Hasson

Le 31/12/2020 à 10:14, Antony Stone a écrit :
On Thursday 31 December 2020 at 10:10:11, jean francois hasson wrote:

If I set up on a device connected to the access point a proxy manually
ie 10.3.141.1 on port 8080, I can access the internet. If I put the
following rules for iptables to use in files rules.v4 :

*nat
-A PREROUTING -i eth0 -p tcp -m tcp --dport 80 -j DNAT --to-destination
10.3.141.1:3128
-A PREROUTING -i eth0 -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128
-A PREROUTING -i eth0 -p tcp -m tcp --dport 443 -j DNAT --to-destination
10.3.141.1:3129
-A PREROUTING -i eth0 -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 3129
-A POSTROUTING -s 10.3.141.0/24 -o eth0 -j MASQUERADE
Try removing the DNAT rules above.  You should be using REDIRECT for intercept
mode to work correctly.


Antony.


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