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completes ssh

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waldek 2021-07-13 14:26:37 +02:00
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modules/qualifying/learning_ssh.md
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@ -13,13 +13,13 @@ You should never use the following the following programs anymore but it's good
* rcp * rcp
* telnet (still has some legitimate usage such as with munin) * telnet (still has some legitimate usage such as with munin)
The main advantage of SSH is it's encryption. The main advantage of SSH is it's **encryption**.
It works similarly to SSL which you use all the time to do most of your web browsing. It works similarly to SSL which you use all the time to do most of your web browsing.
When using encryption it becomes **very** hard to sniff the data traveling between the client and the server. When using encryption it becomes **very** hard to sniff the data traveling between the client and the server.
There are two versions of SSH, version 1 and version 2, and you should only use version 2 as the former is not considered [secure]() anymore. There are two versions of SSH, version 1 and version 2, and you should only use version 2 as the former is not considered [secure]() anymore.
The recommended encryption used by most SSH servers is [AES](https://en.wikipedia.org/wiki/Advanced_Encryption_Standard). The recommended encryption used by most SSH servers is [AES](https://en.wikipedia.org/wiki/Advanced_Encryption_Standard).
If you're interested in understanding the mathematics behind AES, [this](https://www.youtube.com/channel/UC1usFRN4LCMcfIV7UjHNuQg) class is exceptionally good but not for the faint of heart. If you're interested in understanding the mathematics behind AES, [this](https://www.youtube.com/channel/UC1usFRN4LCMcfIV7UjHNuQg) class is exceptionally good but not for the faint of heart.
It's not mandatory to fully understand the math behind encryption to use it though. It's however not mandatory to fully understand the math behind encryption to use it though.
The main takeaway would be the number of **bit's used** where **higher** is **better**. The main takeaway would be the number of **bit's used** where **higher** is **better**.
By default ssh uses a very secure cipher but you can specify which one you want with the `-c` flag to `ssh`. By default ssh uses a very secure cipher but you can specify which one you want with the `-c` flag to `ssh`.
Do keep in mind that the server needs to support the cipher you're requesting. Do keep in mind that the server needs to support the cipher you're requesting.
@ -227,6 +227,31 @@ permitted by applicable law.
student@helloworld:~$ student@helloworld:~$
``` ```
So, how did I add my public key to the `student`'s account authorized keys?
There is a program called `ssh-copy-id` that can do it for you, but I personally always just copy and paste it to the users `~/.ssh/authorized_keys` file.
This is an example of a server I use with the public keys that are allowed to log in.
As you can see there are **four** key's that are allowed to log in.
```
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC9FDWJ6Dr45xQsv/dwqxBVtXuHORtfKtw7tuIe0nq4wRAhdz9XGJ+3s1Czj2YvlMV6rjxjpShG39A6Tnj9oQmqcWdxhmrXAjBQNgVJP6Gpg1NaXSsysEDcKjOcKqqwCHxQ6mYZCl7/vtQotZsTQ+aQW65+D+L6vxNEO6m+XDI283dM1FGQhn7OAN/tZf+tLRT6A4QCF1YEtb2uOsNsU8B+ilBNreqekvJRJ2dYT2QHdNdS2aEMhnHWzsnh4f2bzbpugoiWPGKiHwazePisWUU2/DjQmDq6d3sJ4AeQCt8R4ZlptOleGLdTNCjhRMDvUAMcNsR9OyeFiSok7DFHQw3Z waldek@leanone
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDGKt7Qn9SSSJ7apRbCAqOYltUP+oM5wOIRQ3TLHwiGPYYHt38XWUrUjklRKWH+hagMnHiPHxbloYTtm/OzS9OXOTQJH4n+5c0Jq3OHrMQDztsqWK//gsxBZd7wlA/j6O/7Pr/6jxL0w+bwt1k+VDZR/3Mms3mRfmvGMeg5Wmr2/5GrTZocrUrKH4zgINoAk+6698T9E4YUQp1SLCg634KHA5HqupB9H7aLMovJ1p4K+qOV/MtspzgDvIkZMTFRZ9JvDqYWovaYlr5/zHBnag6/tPgBl+kmEDx6q8mybdtsB9oeARM2O2KKUISzA0PawBFbCNcI3RUSd91trzlhhUQ8 pi@pizone
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDRFprKfRnfxs5lxJXfB5166OHPHHUFr4x2bqxAUc/vtkfmopytf/rhRtgnUeffoZW+KmzhWXuUKw+AjXOfO2OtsyMkbQoJKb3gsZ+KknsWsLEWCx5f8V0sc7y5UHedAuaE9Ax+KqnbPnXJWNtRVxjJCcsWnZNSKERwSjNV/K4yWsFwcdwQirurLB1AZXF0wSNd9ch4/fNX8CjOTuEkOhsUgZ9NZbNAV0LgiVeqghY9JsNt40kYNYX2BQNWk9oEaKdn0YCP+em6CPrDA6MT/rkScr+DPOGpT6GBtXirj+Krw924KjF6eSH9dnWy/ysKlp0CvflQOaVN1zEVZjDGwiAz waldek@vps-42975ad1
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCnKJ8fwHAEe6NS7MTqlAtqzUzqA0ATibR1XP8nirZritVQv7uDNVH91SKM5GSP5gTOzCmW4NQVVv47KvmRQ6yp6BugCsKL96rPMA6m/b9cTA5YDwm90cfb5I6h+kRL2mp4O63ahgGDAb5XgVy3Tq2qyxLbbkKylhw6VQFsHQXObTevSvMrRzc8t29DwS/tfbhT3R6opa2j+5woXDLpKaHrBsw9LFoelkh8jgQ9fbDx2hXwzeccaT3qpycRjtwhraVtt/FTEpJ60R+ooB/Nx2ndlT4qs3P/G3HFrbvlLzjMGlAcjHNkXgQRy6850ACC8RtM6+s4K1RCNU0fPXSy3tkb waldek@helloworld
```
![ssh connection overview](./assets/ssh_connection_01.jpg)
![ssh communication overview](./assets/ssh_connection_02.jpg)
### Keys for gitea
Now that you know how to **create** your own RSA keys I would like you to:
* create one (and save it somewhere safe)
* use it to push/pull from your personal [gitea](https://gitea.86thumbs.net)
I'll let you figure it out by yourself but if you're stuck have a look at [this](https://gitea.86thumbs.net/user/settings/keys) and [this](https://pandammonium.org/how-to-change-a-git-repository-from-https-to-ssh/).
## Standard usage ## Standard usage
## Tweaking the sshd configuration file ## Tweaking the sshd configuration file