Verify whether a given private SSH key is authorized on a series of remote servers.

ssh-auth-check.sh

# Key to test
SSH_KEY_PATH=~/.ssh/id_rsa

# Add SSH key to authentication agent
ssh-add -K ${SSH_KEY_PATH}

echo "Verifying SSH access with key at ${SSH_KEY_PATH}"

for ip in \
    "root@1.2.3.4" \
    "root@5.6.7.8" \
    ; do

    # 2>&1 redirects stderr to stdout
    output=$(ssh -i ${SSH_KEY_PATH} \
    -t "${ip}" 'exit; bash -l' 2>&1)

    [[ $(echo ${output}) =~ "denied" ]] || echo "[   OK   ] ${ip}"
    [[ $(echo ${output}) =~ "closed" ]] || echo "[ DENIED ] ${ip}"

done

# Remove SSH key to authentication agent
ssh-add -d ${SSH_KEY_PATH}

# Print keys in authentication agent
ssh-add -l