[PATCH 1/2] util: extend virGetUserID and virGetGroupID to support names and IDs

[Marcelo Cerri <mhcerri@xxxxxxxxxxxxxxxxxx>]

This patch updates virGetUserID and virGetGroupID to be able to parse a
user or group name in a similar way to coreutils' chown. This means that
a numeric value with a leading plus sign is always parsed as an ID,
otherwise the functions try to parse the input first as a user or group
name and if this fails they try to parse it as an ID.
---
 src/util/util.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 74 insertions(+), 13 deletions(-)

diff --git a/src/util/util.c b/src/util/util.c
index 43fdaf1..694ed3d 100644
--- a/src/util/util.c
+++ b/src/util/util.c
@@ -2495,9 +2495,11 @@ char *virGetGroupName(gid_t gid)
     return virGetGroupEnt(gid);
 }
 
-
-int virGetUserID(const char *name,
-                 uid_t *uid)
+/* Search in the password database for a user id that matches the user name
+ * `name`. Returns 0 on success, -1 on a critical failure or 1 if name cannot
+ * be parsed.
+ */
+static int virGetUserIDByName(const char *name, uid_t *uid)
 {
     char *strbuf;
     struct passwd pwbuf;
@@ -2530,11 +2532,10 @@ int virGetUserID(const char *name,
         }
     }
     if (rc != 0 || pw == NULL) {
-        virReportSystemError(rc,
-                             _("Failed to find user record for name '%s'"),
-                             name);
+        VIR_DEBUG("Failed to find user record for user '%s' (error = %d)",
+                  name, rc);
         VIR_FREE(strbuf);
-        return -1;
+        return 1;
     }
 
     *uid = pw->pw_uid;
@@ -2544,9 +2545,41 @@ int virGetUserID(const char *name,
     return 0;
 }
 
+/* Try to match a user id based on `user`. The default behavior is to parse
+ * `user` first as a user name and then as a user id. However if `user`
+ * contains a leading '+', the rest of the string is always parsed as a uid.
+ *
+ * Returns 0 on success and -1 otherwise.
+ */
+int virGetUserID(const char *user, uid_t *uid)
+{
+    unsigned int uint_uid;
 
-int virGetGroupID(const char *name,
-                  gid_t *gid)
+    if (*user == '+') {
+        user++;
+    } else {
+        int rc = virGetUserIDByName(user, uid);
+        if (rc <= 0)
+            return rc;
+    }
+
+    if (virStrToLong_ui(user, NULL, 10, &uint_uid) < 0 ||
+        ((uid_t) uint_uid) != uint_uid) {
+        virReportError(VIR_ERR_INVALID_ARG, _("Failed to parse user '%s'"),
+                       user);
+        return -1;
+    }
+
+    *uid = uint_uid;
+
+    return 0;
+}
+
+/* Search in the group database for a group id that matches the group name
+ * `name`. Returns 0 on success, -1 on a critical failure or 1 if name cannot
+ * be parsed.
+ */
+static int virGetGroupIDByName(const char *name, gid_t *gid)
 {
     char *strbuf;
     struct group grbuf;
@@ -2579,11 +2612,10 @@ int virGetGroupID(const char *name,
         }
     }
     if (rc != 0 || gr == NULL) {
-        virReportSystemError(rc,
-                             _("Failed to find group record for name '%s'"),
-                             name);
+        VIR_DEBUG("Failed to find group record for group '%s' (error = %d)",
+                  name, rc);
         VIR_FREE(strbuf);
-        return -1;
+        return 1;
     }
 
     *gid = gr->gr_gid;
@@ -2593,6 +2625,35 @@ int virGetGroupID(const char *name,
     return 0;
 }
 
+/* Try to match a group id based on `group`. The default behavior is to parse
+ * `group` first as a group name and then as a group id. However if `group`
+ * contains a leading '+', the rest of the string is always parsed as a guid.
+ *
+ * Returns 0 on success and -1 otherwise.
+ */
+int virGetGroupID(const char *group, gid_t *gid)
+{
+    unsigned int uint_gid;
+
+    if (*group == '+') {
+        group++;
+    } else {
+        int rc = virGetGroupIDByName(group, gid);
+        if (rc <= 0)
+            return rc;
+    }
+
+    if (virStrToLong_ui(group, NULL, 10, &uint_gid) < 0 ||
+        ((gid_t) uint_gid) != uint_gid) {
+        virReportError(VIR_ERR_INVALID_ARG, _("Failed to parse user '%s'"),
+                       group);
+        return -1;
+    }
+
+    *gid = uint_gid;
+
+    return 0;
+}
 
 /* Set the real and effective uid and gid to the given values, and call
  * initgroups so that the process has all the assumed group membership of
-- 
1.7.12

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