acct-user.eclass: allow opt-out of user modification

In some setups where users are changed/managed not only via ebuilds,
for example through configuration management systems, it could be
problematic if acct-user.eclass will restore user/group settings
to values set in ebuild.

Setting ACCT_USER_NO_MODIFY to a non-zero value will allow system
administrator to disable modification of any existing user.

Note: Lock/unlock when acct-* package will be installed/removed
      will still happen.

Signed-off-by: Thomas Deutschmann <whissi@gentoo.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/eclass/acct-user.eclass b/eclass/acct-user.eclass
index ba2fff43a191..ee4358b5c75c 100644
--- a/eclass/acct-user.eclass
+++ b/eclass/acct-user.eclass
@@ -73,6 +73,11 @@ readonly ACCT_USER_NAME
 # Overlays should set this to -1 to dynamically allocate UID.  Using -1
 # in ::gentoo is prohibited by policy.
 
+# @ECLASS-VARIABLE: _ACCT_USER_ALREADY_EXISTS
+# @INTERNAL
+# @DESCRIPTION:
+# Status variable which indicates if user already exists.
+
 # @ECLASS-VARIABLE: ACCT_USER_ENFORCE_ID
 # @DESCRIPTION:
 # If set to a non-null value, the eclass will require the user to have
@@ -80,6 +85,13 @@ readonly ACCT_USER_NAME
 # the UID is taken by another user, the install will fail.
 : ${ACCT_USER_ENFORCE_ID:=}
 
+# @ECLASS-VARIABLE: ACCT_USER_NO_MODIFY
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# If set to a non-null value, the eclass will not make any changes
+# to an already existing user.
+: ${ACCT_USER_NO_MODIFY:=}
+
 # @ECLASS-VARIABLE: ACCT_USER_SHELL
 # @DESCRIPTION:
 # The shell to use for the user.  If not specified, a 'nologin' variant
@@ -390,6 +402,13 @@ acct-user_src_install() {
 acct-user_pkg_preinst() {
 	debug-print-function ${FUNCNAME} "${@}"
 
+	# check if user already exists
+	_ACCT_USER_ALREADY_EXISTS=
+	if [[ -n $(egetent passwd "${ACCT_USER_NAME}") ]]; then
+		_ACCT_USER_ALREADY_EXISTS=1
+	fi
+	readonly _ACCT_USER_ALREADY_EXISTS
+
 	enewuser ${ACCT_USER_ENFORCE_ID:+-F} -M "${ACCT_USER_NAME}" \
 		"${_ACCT_USER_ID}" "${_ACCT_USER_SHELL}" "${_ACCT_USER_HOME}" \
 		"${_ACCT_USER_GROUPS// /,}"
@@ -425,6 +444,14 @@ acct-user_pkg_postinst() {
 		return 0
 	fi
 
+	if [[ -n ${ACCT_USER_NO_MODIFY} && -n ${_ACCT_USER_ALREADY_EXISTS} ]]; then
+		eunlockuser "${ACCT_USER_NAME}"
+
+		ewarn "User ${ACCT_USER_NAME} already exists; Not touching existing user"
+		ewarn "due to set ACCT_USER_NO_MODIFY."
+		return 0
+	fi
+
 	# NB: eset* functions check current value
 	esethome "${ACCT_USER_NAME}" "${_ACCT_USER_HOME}"
 	esetshell "${ACCT_USER_NAME}" "${_ACCT_USER_SHELL}"