Repository: felipe-lavratti/ssh-allow-friend
Branch: master
Commit: aa59f367d570
Files: 5
Total size: 5.9 KB

Directory structure:
gitextract_6i_iabsu/

├── .travis.yml
├── LICENSE.md
├── README.md
├── ssh-allow-friend
└── test.sh

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FILE CONTENTS
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================================================
FILE: .travis.yml
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os:
  - linux
  - osx

script: ./test.sh


================================================
FILE: LICENSE.md
================================================
Copyright (c) 2017: Felipe Lavratti

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


================================================
FILE: README.md
================================================
**ssh-allow-friend**

This is a bash script to temporarily allow a ssh login using friends public key
automatically fetched from online servers.

Example usage:
```sh
./ssh-allow-friend --github my-friend-user-name
```

The script will fetch `my-friend-user-name`'s public key from github and add to
current user authorized keys. After running the command, in a machine where
$USER is `fanl` and the local ip is `192.168.2.13`, the script will print:

```
Acquired key for user my-friend-user-name from github,
your friend is now able to login via ssh using:
    ssh fanl@192.168.2.13

Login authorization will be ceased after this
program terminates.
Press ^C to exit.
```

Your friend can now login with the command `fanl@192.168.2.13`.

If you need to select a different user to your friend ssh session, use:

```sh
sudo -H -u another_user ./ssh-allow-friend --github my-friend-user-name
```


================================================
FILE: ssh-allow-friend
================================================
#!/bin/bash

print_help () {
    echo ""
    echo "    Temporarily allow a ssh login using friends public key"
    echo " fetched from online servers."
    echo ""
    echo "Usage:"
    echo "    $0 [options] <friend_user_name>"
    echo ""
    echo "[options]"
    echo "    -h | --help          Print this help;"
    echo "    -g | --github        Select Github as public key server."
    echo ""
    echo "<friend_user_name>"
    echo "    It is the username used to download keys from selected"
    echo "    server."
    echo ""
    echo "Advanced example:"
    echo ""
    echo "    Allow user \`john-doe\` from Github to login as user"
    echo "    \`myself\`:"
    echo "      sudo -H -u myself $0 --github john-doe"
    echo ""
}

print_usage () {
    echo "Usage example: $0 --github <user_name>"
}

#
# Configuration vars
GITHUB=0
USERNAME=''
USERKEY=''
SERVICENAME=''
LOCALIPADDRESS=''

#
# Test dependencies
getopt --test > /dev/null
if [[ $? -ne 4 ]]; then
    echo "$0: \`getopt --test\` failed in this environment."
    exit 1
fi

curl --help > /dev/null
if [[ $? -ne 0 ]]; then
    echo "$0: \`curl --help\` failed in this environment."
    exit 1
fi

IP_CMD=$(which ip 2> /dev/null)
if [[ $? -ne 0 ]]; then
    echo "$0: ip command not available."
    exit 1
fi

SSH_KEYGEN_CMD=$(which ssh-keygen 2> /dev/null)
if [[ $? -ne 0 ]]; then
    echo "$0: ssh-keygen command not available."
    exit 1
fi

#
# Parse arguments
SHORT=gh
LONG=github,help

PARSED=`getopt --options $SHORT --longoptions $LONG --name "$0" -- "$@"`
if [[ $? -ne 0 ]]; then
    # e.g. $? == 1
    echo "$0: Invalid parameters."
    print_usage
    exit 2
fi
eval set -- "$PARSED"

while true; do
    case "$1" in
        -h|--help)
            print_help
            exit 0
            ;;
        -g|--github)
            GITHUB=1
            shift
            ;;
        --)
            shift
            break
            ;;
        *)
            echo "Programming error"
            exit 3
            ;;
    esac
done

if [[ $# -ne 1 ]]; then
    echo "$0: A single user name is required."
    print_usage
    exit 4
fi

USERNAME=$1

#
# Get user keys from server
github_download_key () {
    SERVICENAME='github'
    USERKEY=`curl -s https://github.com/$USERNAME.keys`

    if [[ -z $USERKEY ]]; then
        echo "User $USERNAME has no keys in Github."
        exit 5
    fi

    if [[ "$USERKEY" == "Not Found" ]]; then
        echo "User $USERNAME not found in Github."
        exit 5
    fi
}

if [[ $GITHUB -eq 1 ]]; then
    github_download_key
else
    echo "$0: No service selected."
    print_usage
    exit 5
fi

#
# Check keys integrity
TMP_KEY_FILE=/tmp/.ssh-allow-friend.$USERNAME-$USER-$SERVICENAME.keys
echo $USERKEY > $TMP_KEY_FILE
ssh-keygen -l -f $TMP_KEY_FILE > /dev/null
if [[ $? -ne 0 ]]; then
    echo "$0: Downloaded key is invalid."
    exit 6
fi
rm -f $TMP_KEY_FILE


#
# Get local ip address
LOCALIPADDRESS=$($IP_CMD -o addr show scope global | awk '{gsub(/\/.*/,"",$4); print $4}')

echo "Acquired key for user $USERNAME from $SERVICENAME,"
echo "your friend is now able to login via ssh using:"
echo "$LOCALIPADDRESS" | while read a; do echo "    ssh $USER@$a"; done
echo ""
echo "Login authorization will be ceased after this program"
echo "terminates."
echo "Press ^C to exit."

setup () {
    (
        flock 200

        mkdir -p $HOME/.ssh/
        echo "$USERKEY" >> $HOME/.ssh/authorized_keys
    ) 200>/tmp/.ssh-allow-friend.$USER.lock
}

teardown () {
    (
        flock 200

        # remove key from file, or the entire file if empty
        if grep -v "$USERKEY" $HOME/.ssh/authorized_keys > $HOME/.ssh/tmp; then
            cat $HOME/.ssh/tmp > $HOME/.ssh/authorized_keys && rm $HOME/.ssh/tmp;
        else
            rm $HOME/.ssh/authorized_keys && rm $HOME/.ssh/tmp;
        fi
    ) 200>/tmp/.ssh-allow-friend.$USER.lock
}

trap "teardown; exit 0" SIGHUP SIGINT SIGTERM
setup
sleep infinity &
wait


================================================
FILE: test.sh
================================================
#!/bin/bash
set -e

./ssh-allow-friend -g flplv &
sleep 10
cat $HOME/.ssh/authorized_keys
kill $!