【Git笔记】"error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed"解决方法

        使用git通过https方式从github clone git repo源码时，报错如下：

Cloning into 'git'...
fatal: unable to access 'https://github.com/git/git.git/': SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

        开启curl verbose选项（用于调试）并重新执行git clone，详细报错信息：

$ export GIT_CURL_VERBOSE=1
$ git clone https://github.com/git/git.git   
Cloning into 'git'...
* Couldn't find host github.com in the .netrc file, using defaults
* About to connect() to github.com port 443
*   Trying 192.30.252.128... * connected
* Connected to github.com (192.30.252.128) port 443
* successfully set certificate verify locations:
*   CAfile: /usr/share/ssl/certs/ca-bundle.crt
  CApath: none
* SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
* Closing connection #0
fatal: unable to access 'https://github.com/git/git.git/': SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

        从错误提示可知，git通过curl访问https地址时，未能在本机未找到ca证书，从而导致ssl certificate verify failed。

        解决方法：
         Setp1： 从curl官网下载cacert.pem文件（下载链接参见 这里 ，关于curl的Server SSL Certificates细节参见 这里 ，其中提到，从curl  7.18.0开始，编译安装curl时默认安装ca证书，而我机器的curl version=7.12.1，curl --version可查看）：

      ~$ mkdir ~/tools/https-ca
      ~$ cd ~/tools/https-ca
      ~$ curl http://curl.haxx.se/ca/cacert.pem -o cacert.pem

        Step2：终端执行下面的命令，以便为git配置ca认证信息：    

      ~$ git config --global http.sslCAInfo /home/slvher/tools/https-ca/cacert.pem

        可打开~/.gitconfig确认cainfo配置成功写入git配置文件

        完成以上两步后，执行git clone https://github.com/git/git.git成功，问题解决。

【参考资料】
1. StackOverflow: SSL certificate rejected trying to access GitHub over HTTPS behind firewall
2. cURL: Details on Server SSL Certificates

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