[libvirt] [PATCH v3 02/18] security: Include security_util

This file implements wrappers over XATTR getter/setter. It ensures the proper XATTR namespace is used. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/security/Makefile.inc.am | 2 + src/security/security_util.c | 256 +++++++++++++++++++++++++++++++++++ src/security/security_util.h | 32 +++++ 3 files changed, 290 insertions(+) create mode 100644 src/security/security_util.c create mode 100644 src/security/security_util.h diff --git a/src/security/Makefile.inc.am b/src/security/Makefile.inc.am index f88b82df7b..0ade97d355 100644 --- a/src/security/Makefile.inc.am +++ b/src/security/Makefile.inc.am @@ -14,6 +14,8 @@ SECURITY_DRIVER_SOURCES = \ security/security_dac.c \ security/security_manager.h \ security/security_manager.c \ + security/security_util.h \ + security/security_util.c \ $(NULL) SECURITY_DRIVER_SELINUX_SOURCES = \ diff --git a/src/security/security_util.c b/src/security/security_util.c new file mode 100644 index 0000000000..194343c407 --- /dev/null +++ b/src/security/security_util.c @@ -0,0 +1,256 @@ +/* + * Copyright (C) 2018 Red Hat, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library. If not, see + * <http://www.gnu.org/licenses/>;. + */ + +#include <config.h> + +#include "viralloc.h" +#include "virfile.h" +#include "virstring.h" +#include "virerror.h" + +#include "security_util.h" + +#define VIR_FROM_THIS VIR_FROM_SECURITY + +/* There are four namespaces available on Linux (xattr(7)): + * + * user - can be modified by anybody, + * system - used by ACLs + * security - used by SELinux + * trusted - accessibly by CAP_SYS_ADMIN processes only + * + * Looks like the last one is way to go. + * Unfortunately, FreeBSD only supports: + * + * user - can be modified by anybody, + * system - accessible by CAP_SYS_ADMIN processes only + * + * Note that 'system' on FreeBSD corresponds to 'trusted' on + * Linux. So far the only point where FreeBSD and Linux can meet + * is NFS which still doesn't support XATTRs. Therefore we can + * use different namespace on each system. If NFS gains support + * for XATTRs then we have to find a way to deal with the + * different namespaces. But that is a problem for future me. + */ +#if defined(__linux__) +# define XATTR_NAMESPACE "trusted" +#elif defined(__FreeBSD__) +# define XATTR_NAMESPACE "system" +#endif + +static char * +virSecurityGetAttrName(const char *name ATTRIBUTE_UNUSED) +{ + char *ret = NULL; +#ifdef XATTR_NAMESPACE + ignore_value(virAsprintf(&ret, XATTR_NAMESPACE".libvirt.security.%s", name)); +#else + errno = ENOSYS; + virReportSystemError(errno, "%s", + _("Extended attributes are not supported on this system")); +#endif + return ret; +} + + +static char * +virSecurityGetRefCountAttrName(const char *name ATTRIBUTE_UNUSED) +{ + char *ret = NULL; +#ifdef XATTR_NAMESPACE + ignore_value(virAsprintf(&ret, XATTR_NAMESPACE".libvirt.security.ref_%s", name)); +#else + errno = ENOSYS; + virReportSystemError(errno, "%s", + _("Extended attributes are not supported on this system")); +#endif + return ret; +} + + +/** + * virSecurityGetRememberedLabel: + * @name: security driver name + * @path: file name + * @label: label + * + * For given @path and security driver (@name) fetch remembered + * @label. The caller must not restore label if an error is + * indicated or if @label is NULL upon return. + * + * The idea is that the first time + * virSecuritySetRememberedLabel() is called over @path the + * @label is recorded and refcounter is set to 1. Each subsequent + * call to virSecuritySetRememberedLabel() increases the counter. + * Counterpart to this is virSecurityGetRememberedLabel() which + * decreases the counter and reads the @label only if the counter + * reached value of zero. For any other call (i.e. when the + * counter is not zero), virSecurityGetRememberedLabel() set + * @label to NULL (to notify the caller that the refcount is not + * zero) and returns zero. + * + * Returns: 0 on success, + * -1 otherwise (with error reported) + */ +int +virSecurityGetRememberedLabel(const char *name, + const char *path, + char **label) +{ + char *ref_name = NULL; + char *attr_name = NULL; + char *value = NULL; + unsigned int refcount = 0; + int ret = -1; + + *label = NULL; + + if (!(ref_name = virSecurityGetRefCountAttrName(name))) + goto cleanup; + + if (virFileGetXAttr(path, ref_name, &value) < 0) { + if (errno == ENOSYS || errno == ENODATA || errno == ENOTSUP) { + ret = 0; + } else { + virReportSystemError(errno, + _("Unable to get XATTR %s on %s"), + ref_name, + path); + } + goto cleanup; + } + + if (virStrToLong_ui(value, NULL, 10, &refcount) < 0) { + virReportError(VIR_ERR_INTERNAL_ERROR, + _("malformed refcount %s on %s"), + value, path); + goto cleanup; + } + + VIR_FREE(value); + + refcount--; + + if (refcount > 0) { + if (virAsprintf(&value, "%u", refcount) < 0) + goto cleanup; + + if (virFileSetXAttr(path, ref_name, value) < 0) + goto cleanup; + } else { + if (virFileRemoveXAttr(path, ref_name) < 0) + goto cleanup; + + if (!(attr_name = virSecurityGetAttrName(name))) + goto cleanup; + + if (virFileGetXAttr(path, attr_name, label) < 0) + goto cleanup; + + if (virFileRemoveXAttr(path, attr_name) < 0) + goto cleanup; + } + + ret = 0; + cleanup: + VIR_FREE(value); + VIR_FREE(attr_name); + VIR_FREE(ref_name); + return ret; +} + + +/** + * virSecuritySetRememberedLabel: + * @name: security driver name + * @path: file name + * @label: label + * + * For given @path and security driver (@name), if called the + * first time over @path, set the @label to remember (i.e. the + * original owner of the @path). Any subsequent call over @path + * will increment refcounter. It is strongly recommended that the + * caller checks for the return value and if it is greater than 1 + * (meaning that some domain is already using @path) the current + * label is required instead of setting a new one. + * + * See also virSecurityGetRememberedLabel. + * + * Returns: the new refcount value on success, + * -1 otherwise (with error reported) + */ +int +virSecuritySetRememberedLabel(const char *name, + const char *path, + const char *label) +{ + char *ref_name = NULL; + char *attr_name = NULL; + char *value = NULL; + unsigned int refcount = 0; + int ret = -1; + + if (!(ref_name = virSecurityGetRefCountAttrName(name))) + goto cleanup; + + if (virFileGetXAttr(path, ref_name, &value) < 0) { + if (errno == ENOSYS || errno == ENOTSUP) { + ret = 0; + goto cleanup; + } else if (errno != ENODATA) { + virReportSystemError(errno, + _("Unable to get XATTR %s on %s"), + ref_name, + path); + goto cleanup; + } + } + + if (value && + virStrToLong_ui(value, NULL, 10, &refcount) < 0) { + virReportError(VIR_ERR_INTERNAL_ERROR, + _("malformed refcount %s on %s"), + value, path); + goto cleanup; + } + + VIR_FREE(value); + + refcount++; + + if (refcount == 1) { + if (!(attr_name = virSecurityGetAttrName(name))) + goto cleanup; + + if (virFileSetXAttr(path, attr_name, label) < 0) + goto cleanup; + } + + if (virAsprintf(&value, "%u", refcount) < 0) + goto cleanup; + + if (virFileSetXAttr(path, ref_name, value) < 0) + goto cleanup; + + ret = refcount; + cleanup: + VIR_FREE(value); + VIR_FREE(attr_name); + VIR_FREE(ref_name); + return ret; +} diff --git a/src/security/security_util.h b/src/security/security_util.h new file mode 100644 index 0000000000..a6e67f4390 --- /dev/null +++ b/src/security/security_util.h @@ -0,0 +1,32 @@ +/* + * Copyright (C) 2018 Red Hat, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library. If not, see + * <http://www.gnu.org/licenses/>;. + */ + +#ifndef __SECURITY_UTIL_H__ +# define __SECURITY_UTIL_H__ + +int +virSecurityGetRememberedLabel(const char *name, + const char *path, + char **label); + +int +virSecuritySetRememberedLabel(const char *name, + const char *path, + const char *label); + +#endif /* __SECURITY_UTIL_H__ */ -- 2.19.2