env-util: replace unsetenv_erase() by new getenv_steal_erase() helper

The new helper combines a bunch of steps every invocation of
unsetenv_erase() did so far: getenv() + strdup() + unsetenv_erase().
Let's unify this into one helper that is harder to use incorrectly. It's
in inspired by TAKE_PTR() in a way: get the env var out and invalidate
where it was before.

2 files changed, 11 insertions, 24 deletions

diff --git a/src/cryptenroll/cryptenroll-password.c b/src/cryptenroll/cryptenroll-password.c
index 1775912d8e..9b7c8b5400 100644
--- a/src/cryptenroll/cryptenroll-password.c
+++ b/src/cryptenroll/cryptenroll-password.c
@@ -17,20 +17,13 @@ int enroll_password(
         _cleanup_free_ char *error = NULL;
         const char *node;
         int r, keyslot;
-        char *e;
 
         assert_se(node = crypt_get_device_name(cd));
 
-        e = getenv("NEWPASSWORD");
-        if (e) {
-
-                new_password = strdup(e);
-                if (!new_password)
-                        return log_oom();
-
-                assert_se(unsetenv_erase("NEWPASSWORD") >= 0);
-
-        } else {
+        r = getenv_steal_erase("NEWPASSWORD", &new_password);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire password from environment: %m");
+        if (r == 0) {
                 _cleanup_free_ char *disk_path = NULL;
                 unsigned i = 5;
                 const char *id;
diff --git a/src/cryptenroll/cryptenroll.c b/src/cryptenroll/cryptenroll.c
index c9bc9a2489..e13f5b7ac8 100644
--- a/src/cryptenroll/cryptenroll.c
+++ b/src/cryptenroll/cryptenroll.c
@@ -409,8 +409,8 @@ static int prepare_luks(
                 size_t *ret_volume_key_size) {
 
         _cleanup_(crypt_freep) struct crypt_device *cd = NULL;
+        _cleanup_(erase_and_freep) char *envpw = NULL;
         _cleanup_(erase_and_freep) void *vk = NULL;
-        char *e = NULL;
         size_t vks;
         int r;
 
@@ -445,23 +445,17 @@ static int prepare_luks(
         if (!vk)
                 return log_oom();
 
-        e = getenv("PASSWORD");
-        if (e) {
-                _cleanup_(erase_and_freep) char *password = NULL;
-
-                password = strdup(e);
-                if (!password)
-                        return log_oom();
-
-                assert_se(unsetenv_erase("PASSWORD") >= 0);
-
+        r = getenv_steal_erase("PASSWORD", &envpw);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire password from environment: %m");
+        if (r > 0) {
                 r = crypt_volume_key_get(
                                 cd,
                                 CRYPT_ANY_SLOT,
                                 vk,
                                 &vks,
-                                password,
-                                strlen(password));
+                                envpw,
+                                strlen(envpw));
                 if (r < 0)
                         return log_error_errno(r, "Password from environment variable $PASSWORD did not work.");
         } else {