Enjoy Slackware 15.0!
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
|
howtos:misc:proxying_smtp [2015/11/27 23:01 (UTC)] louigi600 [Scenario 2] |
howtos:misc:proxying_smtp [2016/04/28 07:38 (UTC)] louigi600 [Scenario 3] |
||
|---|---|---|---|
| Line 6: | Line 6: | ||
| Here are some scenarios with examples on how you could go about working around the problem. | Here are some scenarios with examples on how you could go about working around the problem. | ||
| - | Throughout the scenarios we will be referring | + | Throughout the scenarios we will be referring |
| - | Machine A with IP address 192.168.0.2 (cannot send meils directly via internet and cannot | + | * Machine A with IP address 192.168.0.2 (cannot send mails directly via internet and cannot |
| - | + | | |
| - | Machine B with IP address 192.168.1.2 | + | |
| - | + | ||
| - | Local Mail Relay (LMR) with IP address 192.168.2.2 | + | |
| ===== Scenario 1 ===== | ===== Scenario 1 ===== | ||
| - | Machine A cannot | + | * Machine A cannot |
| - | but Machine A has access to machine | + | |
| + | * Machine B can relay thought LMR | ||
| + | * Machine B can reach LMR's port 25 | ||
| - | We can use nc to proxy mail from A to LMR | + | We can use nc on Machine B to proxy mail from A to LMR. In this example it will appear to LMR as if it was Machine B that is sending the email. |
| On machine B | On machine B | ||
| Line 55: | Line 55: | ||
| ===== Scenario 2 ===== | ===== Scenario 2 ===== | ||
| - | Let' | + | * Machine A cannot reach LMR' |
| - | can we use a ssh tunnel between A and LMR to do the job for us ? | + | * Machine A is allowed to relay thought LMR but firewall is preventing it from reaching port 25 on LMR |
| + | * Machine A can reach the LMR but only on port 22. | ||
| + | |||
| + | We use a ssh tunnel between A and LMR to do the job for us. In this example we are bypassing firewall by using ssh to forward traffic trough a encrypted tunnel. For this to work properly the ssh client that is going to be forwarding needs to be executed by an administrative account. | ||
| <note important> | <note important> | ||
| Line 71: | Line 74: | ||
| DATA | DATA | ||
| 354 End data with < | 354 End data with < | ||
| - | FROM:drao@invallee.it | + | FROM:me@localnet.com |
| - | TO:drao@invallee.it | + | TO:dude@localnet.com |
| SUBJECT: | SUBJECT: | ||
| if you get this sending email trough ssh tunnel worked | if you get this sending email trough ssh tunnel worked | ||
| Line 82: | Line 85: | ||
| - | + | ===== Scenario 3 ===== | |
| - | This method may or may not work depending on whether MTA on LMR is configured to allow Machine A to relay trought it. This leads to yet another scenario (see Scenario 3) or an alternative method provided the following conditions are met: | + | |
| * Machine B can relay emails trough LMR | * Machine B can relay emails trough LMR | ||
| + | * Machine B cannot reach LMR's port 25 | ||
| + | * Machine B can access LMR via ssh | ||
| * Machine A has access to Machine B on whatever port we choose to let ssh listen on for forwarding (1024 in the exaple). | * Machine A has access to Machine B on whatever port we choose to let ssh listen on for forwarding (1024 in the exaple). | ||
| Line 91: | Line 95: | ||
| We can then start the ssh socks proxy on Machine B listening on a port Machine A can access: | We can then start the ssh socks proxy on Machine B listening on a port Machine A can access: | ||
| - | On machine B | + | On machine B with a privileged user |
| ssh -2 -D 192.168.1.2: | ssh -2 -D 192.168.1.2: | ||
| Line 105: | Line 109: | ||
| DATA | DATA | ||
| 354 End data with < | 354 End data with < | ||
| - | FROM:drao@invallee.it | + | FROM:me@localnet.com |
| - | TO:drao@invallee.it | + | TO:dude@localnet.com |
| SUBJECT: | SUBJECT: | ||
| if you get this sending email trough ssh tunnel worked | if you get this sending email trough ssh tunnel worked | ||
| Line 116: | Line 120: | ||
| - | ===== Scenario | + | ===== Scenario |
| - | Mostly like Scenario 2 but Machine A is not allowed to relay on LMR dew to MTA configuration. | + | * Machine A cannot reach LMR's port 25 |
| + | * Machine A is not allowed to relay thought | ||
| + | * Machine A cannot proxy on any other machine that is allowed | ||
| + | * Machine A can reach the LMR but only on port 22. | ||
| We can still get the whole command to run on the LMR via ssh: | We can still get the whole command to run on the LMR via ssh: | ||
| + | |||
| + | <note important> | ||
| cat << EOF > send_this_mail | cat << EOF > send_this_mail | ||
| Line 132: | Line 142: | ||
| quit | quit | ||
| exit | exit | ||
| - | | + | " | curl telnet:// |
| + | EOF | ||
| cat send_this_mail |ssh 192.168.2.2 | cat send_this_mail |ssh 192.168.2.2 | ||
