Permit pre-existing keypair to be used for remote user creation

SSH/Create-SSH-User.bash

@@ -137,30 +137,52 @@ usage() {
 
     Example:
       --user User1")
+
   $(arg_required "-H") <hostName: string> | $(arg_required "--host-name") <hostName: string>
     $(arg_description \
     "The SSH hostname for the given host, MUST exist within your ssh configuration; typically located at ~/.ssh/config
 
     Example:
       --host-name gitlab.orion-technologies.io")
+
   $(arg_optional "-L") <loginUser: string> | $(arg_optional "--login-user") <loginUser: string>
     $(arg_description \
     "The user used to login to your host, must be a privileged sudo user. Default user is root.
 
     Example:
       --login-user Admin")
+
   $(arg_optional "-K") <keyType: string> | $(arg_optional "--key-type") <keyType: string>
     $(arg_description \
     "The SSH key type to generate, passed to ssh-keygen's -t flag.
 
     Example:
       --key-type rsa")
+
   $(arg_optional "-B") <keyBits: int> | $(arg_optional "--bits") <keyBits: int>
     $(arg_description \
     "The number of bits used to generate the given key, default is set at 512.
 
     Example:
-      --bits 2048")"
+      --bits 2048")
+
+  $(arg_optional "-E") <existingPrivateKey: file> | $(arg_optional "--existing-key") <existingPrivateKey: file>
+    $(arg_description \
+    "An existing private key that will be used to login the remote server. An important note, if the --pub-key option
+    is not passed then this will default to looking for the private key file name concatenated with .pub -- for example:
+    given a private-key file named id_rsa, by default this will look for id_rsa.pub in the same directory; this
+    behavior can be overwritten with the --pub-key option below.
+
+    Example:
+      --existing-key ~/.ssh/id_rsa")
+
+  $(arg_optional "-P") <existingPublicKey: file> | $(arg_optional "--pub-key") <existingPublicKey: file>
+    $(arg_description \
+    "An existing public key that will be sent to the remote server's authorized_hosts file.
+    Depends upon the --existing-key option being passed.
+
+    Example:
+      --public-key ~/.ssh/id_rsa.pub")"
 
 }
 
@@ -169,6 +191,8 @@ ssh_host_name=""
 ssh_key_type="ed25519"
 ssh_key_bits=512
 ssh_login_user="root"
+existing_ssh_key=""
+existing_pub_key=""
 
 parse_args() {
   # Parse input arguments
@@ -199,6 +223,28 @@ parse_args() {
         log "error" "No argument provided for ${1}" &&
         exit 1
       ;;
+    -E | --existing-key)
+      existing_ssh_key="${2}"
+      [[ ! -f "${existing_ssh_key}" ]] &&
+        log "error" "Given file, ${existing_ssh_key}, does not exist or is not a file!" &&
+        exit 1
+      local first_line
+      first_line="$(head -n 1 "${existing_ssh_key}")"
+
+      # Remove case sensitivity from string matching
+      shopt -s nocasematch
+      if [[ ! "${first_line}" = *"OPENSSH PRIVATE KEY"* ]]; then
+        log "warning" "Given key, ${existing_ssh_key}, could not be determined to be an OpenSSH Private Key!"
+        sleep 5
+      fi
+      shopt -u nocasematch
+      ;;
+    -P | --pub-key)
+      existing_pub_key="${2}"
+      [[ ! -f "${existing_pub_key}" ]] &&
+        log "error" "Given file, ${existing_pub_key}, does not exist or is not a file!" &&
+        exit 1
+      ;;
     -K | --key-type)
       ssh_key_type="${2}"
       [[ -z "${ssh_key_type}" ]] &&
@@ -238,8 +284,27 @@ parse_args() {
   done
 }
 
+### ENTRY POINT ###
+
 parse_args "$@"
 
+### ENTRY POINT ###
+
+
+### NON-BOILERPLATE FUNCTIONS ###
+
+rollback_ssh() {
+  if [[ -z "${existing_ssh_key}" ]]; then
+    log "info" "Deleting generated SSH keypair"
+    rm "${SSH_KEY_FILE}"{,.pub}
+  fi
+  log "info" "Restoring old SSH Config from ${SSH_BACKUP_FILE}"
+  mv "${SSH_BACKUP_FILE}" "${SSH_CONFIG_FILE}"
+}
+
+
+### PRIMARY LOGIC ###
+
 [[ -z "${ssh_user_to_create}" ]] &&
   log "error" "User may not be empty" &&
   exit 1
@@ -248,41 +313,46 @@ parse_args "$@"
   log "error" "--host-name may not be empty" &&
   exit 1
 
-SSH_KEY_DIRECTORY="${HOME}/.ssh/keys/${ssh_host_name}/"
 
-log "info" "Creating directory ${SSH_KEY_DIRECTORY} for the ssh key if it doesn't exist"
+if [[ -z "${existing_ssh_key}" ]]; then
-mkdir -p "${SSH_KEY_DIRECTORY}" > /dev/null
+  log "info" "Existing key not given, generating a new keypair"
+  SSH_KEY_DIRECTORY="${HOME}/.ssh/keys/${ssh_host_name}/"
 
-SSH_KEY_FILE="${SSH_KEY_DIRECTORY}/${ssh_user_to_create}-id_${ssh_key_type}"
+  log "info" "Creating directory ${SSH_KEY_DIRECTORY} for the ssh key if it doesn't exist"
+  mkdir -p "${SSH_KEY_DIRECTORY}" > /dev/null
 
-[[ -f "${SSH_KEY_FILE}" ]] &&
+  SSH_KEY_FILE="${SSH_KEY_DIRECTORY}/${ssh_user_to_create}-id_${ssh_key_type}"
-  log "error" "${SSH_KEY_FILE} already exists! This may lead to major errors, check your SSH configuration and remove the SSH entry as well as the SSH key file or create a different user if you wish to continue." &&
-  exit 1
 
-log "info" "Generating SSH key file for ${ssh_user_to_create}@${ssh_host_name} at ${SSH_KEY_FILE}"
+  [[ -f "${SSH_KEY_FILE}" ]] &&
-ssh-keygen -b 512 -t ed25519 -f "${SSH_KEY_FILE}" -N "" > /dev/null || exit "${?}"
+    log "error" "${SSH_KEY_FILE} already exists! This may lead to major errors, check your SSH configuration and remove the SSH entry as well as the SSH key file or create a different user if you wish to continue." &&
-chmod 600 "${SSH_KEY_FILE}" > /dev/null
+    exit 1
-log "info" "SSH key successfully created"
 
-PUB_KEY_CONTENTS="$(cat "${SSH_KEY_FILE}.pub")"
+  ssh-keygen -t "${ssh_key_type}" -b "${ssh_key_bits}" -N "" -f "${SSH_KEY_FILE}" > /dev/null
-
+  log "info" "Generated a private key file located at ${SSH_KEY_FILE}"
-log "info" "Logging into remote server as ${ssh_login_user}@${ssh_host_name} to create ${ssh_user_to_create} and directories"
+else
-ssh "${ssh_login_user}"@"${ssh_host_name}" > /dev/null <<__EOF__
+  log "info" "An existing SSH key was given, skipping generation of a keypair"
-sudo useradd ${ssh_user_to_create}
+  SSH_KEY_DIRECTORY="$(dirname "${existing_ssh_key}")"
-mkdir -p /home/${ssh_user_to_create}/.ssh
+  SSH_KEY_FILE="${existing_ssh_key}"
-echo ${PUB_KEY_CONTENTS} >> /home/${ssh_user_to_create}/.ssh/authorized_keys
+  log "info" "SSH key given: ${existing_ssh_key}"
-chown -R ${ssh_user_to_create}:${ssh_user_to_create} /home/${ssh_user_to_create}/.ssh
-__EOF__
-
-if [[ "${?}" -ne "0" ]]; then
-  log "error" "Unable to login to remote server with ${ssh_login_user}@${ssh_host_name}"
-  log "error" "Verify the correct user and host name have been provided and that an SSH configuration exists for the pair in your SSH configuration"
-  rm "${SSH_KEY_FILE}"
-  exit 1
 fi
 
+
+if [[ -z "${existing_pub_key}" ]]; then
+  log "info" "A public key was not given, attempting an automatic public key lookup..."
+  [[ ! -f "${SSH_KEY_FILE}.pub" ]] &&
+    log "error" "Unable to find the corresponding public key for ${SSH_KEY_FILE}, should be ${SSH_KEY_FILE}.pub, if you intend to use a different public key pass the --pub-key option" &&
+    exit 1
+  PUB_KEY_CONTENTS="$(cat "${SSH_KEY_FILE}.pub")" || exit 1
+  log "info" "Found a public key: ${SSH_KEY_FILE}.pub"
+else
+  log "info" "A public key was given, using ${existing_pub_key} for public key"
+  PUB_KEY_CONTENTS="$(cat "${existing_pub_key}")" || exit 1
+fi
+
+log "debug" "Pub key contents: ${PUB_KEY_CONTENTS}"
+
 SSH_CONFIG_FILE="${HOME}/.ssh/config"
-log "info" "Finished creating ${ssh_user_to_create}, generating ssh configuration for ${SSH_CONFIG_FILE}"
+log "info" "Generating ssh configuration for ${SSH_CONFIG_FILE}"
 
 SPACE_PADDING="  "
 SSH_LINES_TO_ADD="${SPACE_PADDING}Match user ${ssh_user_to_create} host ${ssh_host_name}
@@ -300,6 +370,7 @@ log "info" "Searching for a Host entry for ${ssh_host_name} within ${SSH_CONFIG_
 # Remove case sensitivity from string matching
 shopt -s nocasematch
 
+wrote_new_data=0
 should_write=0
 while IFS= read -r line; do
   printf "%s\n" "${line}"
@@ -308,8 +379,48 @@ while IFS= read -r line; do
   fi
   if [[ "${should_write}" -eq "1" ]]; then
     printf "%s\n" "${SSH_LINES_TO_ADD}"
+    wrote_new_data=1
     should_write=0
   fi
 done < "${SSH_CONFIG_FILE}" > "ssh_conf.temp" && mv "ssh_conf.temp" "${SSH_CONFIG_FILE}"
 
-log "info" "Successfully wrote the new SSH configuration, login with ${ssh_user_to_create}@${ssh_host_name}"
+cat "${SSH_CONFIG_FILE}"
+shopt -u nocasematch
+
+if [[ "${wrote_new_data}" -eq "1" ]]; then
+  log "info" "Successfully wrote the new SSH configuration, login with ${ssh_user_to_create}@${ssh_host_name}"
+else
+  log "error" "Failed to write to ${SSH_CONFIG_FILE} -- Most likely cause is a missing HostName for ${ssh_host_name}"
+  rollback_ssh
+  exit 1
+fi
+
+
+log "info" "Logging into remote server as ${ssh_login_user}@${ssh_host_name} to create ${ssh_user_to_create} and directories"
+
+log "info" "Verifying that user has sudo permissions"
+ssh "${ssh_login_user}"@"${ssh_host_name}" sudo -v
+
+SSH_RESULT="${?}"
+if [[ "${SSH_RESULT}" -ne "0" ]]; then
+  log "error" "Unable to login to remote server with ${ssh_login_user}@${ssh_host_name}, received error code "${SSH_RESULT}
+  log "error" "Verify the correct user and host name have been provided and that an SSH configuration exists for the pair in your SSH configuration"
+  rollback_ssh
+  exit "${SSH_RESULT}"
+fi
+
+log "info" "User ${ssh_login_user} has sudo permissions, beginning the creation of user ${ssh_user_to_create} and installing the public key for login"
+
+ssh "${ssh_login_user}"@"${ssh_host_name}" > /dev/null << __EOF__
+sudo useradd ${ssh_user_to_create}
+sudo mkdir -p /home/${ssh_user_to_create}/.ssh
+echo ${PUB_KEY_CONTENTS} | sudo tee -a /home/${ssh_user_to_create}/.ssh/authorized_keys
+sudo chown -R ${ssh_user_to_create}:${ssh_user_to_create} /home/${ssh_user_to_create}/.ssh
+__EOF__
+
+
+SSH_RESULT="${?}"
+if [[ "${SSH_RESULT}" -ne "0" ]]; then
+  log "error" "Second set of SSH commands were unable to execute, ssh returned status code ${SSH_RESULT}"
+  exit "${SSH_RESULT}"
+fi