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[libvirt] [PATCH v2 3/4] virfile: Introduce internal API for managing ACL



For now, only two APIs are implemented:
virFileSetACL for setting requested permissions for a specific user,
virFileRemoveACL to remove those permissions.

Both these traverse the whole path from root directory and set or
unset S_IXUSR flag on all directories met so user can really
access the file.
---
 configure.ac             |   1 +
 libvirt.spec.in          |   3 +
 src/libvirt_private.syms |   2 +
 src/util/virfile.c       | 202 +++++++++++++++++++++++++++++++++++++++++++++++
 src/util/virfile.h       |   7 ++
 5 files changed, 215 insertions(+)

diff --git a/configure.ac b/configure.ac
index cbb20c4..0df8a72 100644
--- a/configure.ac
+++ b/configure.ac
@@ -276,6 +276,7 @@ AM_CONDITIONAL([HAVE_LIBTASN1], [test "x$ac_cv_header_libtasn1_h" = "xyes"])
 
 AC_CHECK_LIB([intl],[gettext],[])
 AC_CHECK_LIB([attr],[getxattr])
+AC_CHECK_LIB([acl], [acl_init])
 
 dnl Do we have rpcgen?
 AC_PATH_PROG([RPCGEN], [rpcgen], [no])
diff --git a/libvirt.spec.in b/libvirt.spec.in
index 90629c8..67c5799 100644
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -580,6 +580,9 @@ BuildRequires: scrub
 # For xattr
 BuildRequires: libattr-devel
 
+# For ACL
+BuildRequires: libacl-devel
+
 %if %{with_numad}
 BuildRequires: numad
 %endif
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index fc7568e..980e3ea 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1275,8 +1275,10 @@ virFileFclose;
 virFileFdopen;
 virFileGetAttr;
 virFileLoopDeviceAssociate;
+virFileRemoveACL;
 virFileRemoveAttr;
 virFileRewrite;
+virFileSetACL;
 virFileSetAttr;
 virFileTouch;
 virFileUpdatePerm;
diff --git a/src/util/virfile.c b/src/util/virfile.c
index aa4579e..5d4254d 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -42,6 +42,11 @@
 # include <sys/types.h>
 #endif
 
+#ifdef HAVE_LIBACL
+# include <sys/acl.h>
+# include <sys/types.h>
+#endif
+
 #include "vircommand.h"
 #include "configmake.h"
 #include "viralloc.h"
@@ -750,3 +755,200 @@ virFileRemoveAttr(const char *file ATTRIBUTE_UNUSED,
     return -1;
 }
 #endif /* HAVE_LIBATTR */
+
+#ifdef HAVE_LIBACL /* HAVE_LIBACL */
+static acl_entry_t
+findACLEntry(acl_t acl, acl_tag_t type, id_t id)
+{
+    acl_entry_t ent;
+    acl_tag_t e_type;
+    id_t *e_id_p;
+
+    /* acl_get_entry returns 1 if there's an entry in @acl */
+    if (acl_get_entry(acl, ACL_FIRST_ENTRY, &ent) != 1)
+        return NULL;
+
+    while (true) {
+        acl_get_tag_type(ent, &e_type);
+        if (e_type == type) {
+            if (id == ACL_UNDEFINED_ID)
+                return ent;
+
+            if (!(e_id_p = acl_get_qualifier(ent)))
+                return NULL;
+            if (*e_id_p == id) {
+                acl_free(e_id_p);
+                return ent;
+            }
+            acl_free(e_id_p);
+        }
+        if (acl_get_entry(acl, ACL_NEXT_ENTRY, &ent) != 1)
+            return NULL;
+    }
+}
+
+static void
+setACLPerms(acl_entry_t ent, mode_t perms)
+{
+    acl_permset_t set;
+
+    acl_get_permset(ent, &set);
+    if (perms & S_IRUSR)
+        acl_add_perm(set, ACL_READ);
+    else
+        acl_delete_perm(set, ACL_READ);
+    if (perms & S_IWUSR)
+        acl_add_perm(set, ACL_WRITE);
+    else
+        acl_delete_perm(set, ACL_WRITE);
+    if (perms & S_IXUSR)
+        acl_add_perm(set, ACL_EXECUTE);
+    else
+        acl_delete_perm(set, ACL_EXECUTE);
+}
+
+static int
+cloneACLEntry(acl_t fromAcl, acl_tag_t fromType, id_t user,
+              acl_t *toAcl, acl_tag_t toType)
+{
+    acl_entry_t fromEntry, toEntry;
+    if (!(fromEntry = findACLEntry(fromAcl, fromType, user)))
+        return 1;
+
+    if (acl_create_entry(toAcl, &toEntry) != 0) {
+        virReportSystemError(errno, "%s", _("Unable to clone ACL entry"));
+        return -1;
+    }
+
+    acl_copy_entry(toEntry, fromEntry);
+    acl_set_tag_type(toEntry, toType);
+    return 0;
+}
+
+static int
+virFileSetOrRemoveACLHelper(const char *path,
+                            uid_t user,
+                            mode_t perms,
+                            bool set)
+{
+    int ret = -1;
+    acl_t acl;
+    acl_entry_t ent;
+
+    if (!(acl = acl_get_file(path, ACL_TYPE_ACCESS))) {
+        virReportSystemError(errno, _("Unable to get ACL on %s"), path);
+        return ret;
+    }
+
+    ent = findACLEntry(acl, ACL_USER, user);
+    if (!ent && set) {
+        if (acl_create_entry(&acl, &ent) < 0) {
+            virReportSystemError(errno, "%s", _("Unable to create ACL entity"));
+            goto cleanup;
+        }
+        acl_set_tag_type(ent, ACL_USER);
+        acl_set_qualifier(ent, &user);
+
+        setACLPerms(ent, perms);
+
+        /* Recompute mask */
+        if (!findACLEntry(acl, ACL_MASK, ACL_UNDEFINED_ID) &&
+            cloneACLEntry(acl, ACL_USER, user, &acl, ACL_MASK) < 0)
+            goto cleanup;
+    } else if (ent && !set) {
+        if (acl_delete_entry(acl, ent) < 0) {
+            virReportSystemError(errno, "%s", _("Unable to delete ACL entity"));
+            goto cleanup;
+        }
+
+        if ((ent = findACLEntry(acl, ACL_MASK, user)) &&
+            acl_delete_entry(acl, ent) < 0) {
+                virReportSystemError(errno, "%s", _("Unable to delete ACL entity"));
+                goto cleanup;
+            }
+    }
+
+    if (acl_set_file(path, ACL_TYPE_ACCESS, acl) < 0) {
+        virReportSystemError(errno, _("Unable to set ACL on %s"), path);
+        goto cleanup;
+    }
+
+    ret = 0;
+cleanup:
+    acl_free(acl);
+    return ret;
+}
+
+static int
+virFileSetOrRemoveACL(const char *file,
+                      uid_t user,
+                      mode_t perms,
+                      bool set)
+{
+    int ret = -1;
+    char *fileDup = NULL;
+    char *p;
+
+    if (!(fileDup = strdup(file))) {
+        virReportOOMError();
+        return ret;
+    }
+
+    if (virFileSetOrRemoveACLHelper(file, user, perms, set) < 0)
+        goto cleanup;
+
+    /* For parent directories we want executable flag */
+    perms |= S_IXUSR;
+
+    while ((p = strrchr(fileDup, '/')) != fileDup) {
+        if (!p) {
+            virReportSystemError(EINVAL, _("Invalid relative path '%s'"), file);
+            goto cleanup;
+        }
+
+        *p = '\0';
+
+        if (virFileSetOrRemoveACLHelper(fileDup, user, perms, set) < 0)
+            goto cleanup;
+    }
+
+    ret = 0;
+
+cleanup:
+    VIR_FREE(fileDup);
+    return ret;
+}
+
+int
+virFileSetACL(const char *file,
+              uid_t user,
+              mode_t perms)
+{
+    return virFileSetOrRemoveACL(file, user, perms, true);
+}
+
+int
+virFileRemoveACL(const char *file,
+                 uid_t user)
+{
+    return virFileSetOrRemoveACL(file, user, 0, false);
+}
+
+#else /* HAVE_LIBACL */
+int
+virFileSetACL(const char *file ATTRIBUTE_UNUSED,
+              uid_t user ATTRIBUTE_UNUSED,
+              mode_t perms ATTRIBUTE_UNUSED)
+{
+    virReportSystemError(ENOSYS, "%s", _("Unable to set ACL"));
+    return -1;
+}
+
+int
+virFileRemoveACL(const char *file ATTRIBUTE_UNUSED,
+                 uid_t user ATTRIBUTE_UNUSED)
+{
+    virReportSystemError(ENOSYS, "%s", _("Unable to remove ACL"));
+    return -1;
+}
+#endif /* HAVE_LIBACL */
diff --git a/src/util/virfile.h b/src/util/virfile.h
index 3b4d672..b530aed 100644
--- a/src/util/virfile.h
+++ b/src/util/virfile.h
@@ -120,4 +120,11 @@ int virFileGetAttr(const char *file,
 int virFileRemoveAttr(const char *file,
                       const char *name);
 
+int virFileSetACL(const char *file,
+                  uid_t user,
+                  mode_t perms);
+
+int virFileRemoveACL(const char *file,
+                     uid_t user);
+
 #endif /* __VIR_FILES_H */
-- 
1.8.1.5


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