# [GitHub] 設定 GitHub SSH 連線

###### tags: `GitHub`

## 檢查是否有任何 SSH key
1. 在終端機輸入 `ls -al ~/.ssh`
2. 若有可用的 SSH key，執行 [將 SSH key 加到 GitHub account](#將-SSH-key-加到-GitHub-account)
3. 若無適合的檔案或看到 `No such file or directory` 之類的訊息（代表沒有任何 SSH key），執行 [產生新的 SSH key](#產生新的-SSH-key)

## 產生新的 SSH key
1. 在終端機輸入 `ssh-keygen -t ed25519 -C "你的 GitHub email"`
2. 會出現確認訊息，若不打算變更檔案儲存的位置或名稱，直接按 `Enter` 鍵
* 若要修改，輸入要儲存的位置及檔名，例：`/Users/xxxx/.ssh/github_xxxx_ed25519`

    Generating public/private ed25519 key pair.
    Enter file in which to save the key (/Users/xxxx/.ssh/id_ed25519):

4. 設定密碼，若不打算設定密碼，不輸入任何字直接按 `Enter` 鍵
* 若有設定密碼，但不想每次使用時都要輸入密碼，可考慮將 key 加到 SSH agent，詳細步驟可參考 [GitHub Docs - Adding your SSH key to the ssh-agent](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent#adding-your-ssh-key-to-the-ssh-agent)

    # 若沒有 .ssh 資料夾，會自動創建
    Created directory '/Users/xxxx/.ssh'.
    
    Enter passphrase (empty for no passphrase):
    Enter same passphrase again:

6. 產生 SSH key

    Your identification has been saved in /Users/xxxx/.ssh/id_ed25519
    Your public key has been saved in /Users/xxxx/.ssh/id_ed25519.pub
    The key fingerprint is:
    SHA256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

## 將 SSH key 加到 GitHub account
網址：[GitHub SSH and GPG keys](https://github.com/settings/keys)
1. 點 `New SSH Key` 按鈕
2. 輸入 `Title` 內容
3. 將公鑰 `.pub` 內容複製貼到 `Key` 欄位
4. 點 `Add SSH Key` 按鈕

## 測試和 GitHub 的 SSH 連線
1. 在終端機輸入以下內容`ssh -T [e-mail]`

### 失敗
#### 失敗訊息一

The authenticity of host 'github.com (IP ADDRESS)' can't be established.
ED25519 key fingerprint is SHA256:+DiY3wvvV6TuJJhbpZisF/zLDA0zPMSvHdkr4UvCOqU.
Are you sure you want to continue connecting (yes/no)?

* 檢查訊息中的 fingerprint 是否和 [GitHub's public key fingerprint](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints) 匹配，是的話輸入 `yes`
#### 失敗訊息二

[e-mail]: Permission denied (publickey).

* 檢查是否有文件中提到的狀況 [Error: Permission denied (publickey) - GitHub Docs](https://docs.github.com/en/authentication/troubleshooting-ssh/error-permission-denied-publickey)
* 若有變更 SSH key 檔名
* GitHub 支援的公鑰的檔名為 `id_rsa.pub` 或 `id_ecdsa.pub` 或 `id_ed25519.pub`，若檔名不同，要 [設定 config](#設定-config)
* 設定 config 後，測試連線的指令要改成 `ssh -T git@設定的Host alias`，例：`ssh -T git@github-xxxx`

### 成功
#### 成功訊息

Hi USERNAME! You've successfully authenticated, but GitHub does not provide shell access.

## 設定 config
在 `~/.ssh` 資料夾內新增 `config` 檔案，範例如下

# Host               alias
# HostName           domain 或 ip
# Port               port
# IdentitiesOnly     指定key，值: yes
# IdentityFile       指定的 key 路徑和檔名
# User               登入的 username

# GitHub xxxx
Host github-xxxx
  HostName github.com
  IdentitiesOnly yes
  IdentityFile ~/.ssh/github_xxxx_ed25519

* 若有自訂的 Host 名稱，clone repository 時不能直接使用 `GitHub` > `Clone` > `SSH` 提供的 URL
* 例：`[e-mail]:帳號/repository-name.git` 要改成 `git@github-xxxx:帳號/repository-name.git`

## 參考資料
* [Checking for existing SSH keys - GitHub Docs](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/checking-for-existing-ssh-keys)
* [Generating a new SSH key and adding it to the ssh-agent - GitHub Docs](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent)
* [Adding a new SSH key to your GitHub account - GitHub Docs](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/adding-a-new-ssh-key-to-your-github-account)
* [Testing your SSH connection - GitHub Docs](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/testing-your-ssh-connection)
* [【Git】使用 SSH 金鑰與 GitHub 連線 by 辛西亞．Cynthia](https://cynthiachuang.github.io/Generating-a-Ssh-Key-and-Adding-It-to-the-Github/)

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:::info
建立日期：2024-01-21
更新日期：2024-01-22
:::