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Message-Id: <1527250929.3424.146.camel@linux.vnet.ibm.com>
Date: Fri, 25 May 2018 08:22:09 -0400
From: Mimi Zohar <zohar@...ux.vnet.ibm.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
"Luis R . Rodriguez" <mcgrof@...nel.org>,
kexec@...ts.infradead.org, Andres Rodriguez <andresx7@...il.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Kees Cook <keescook@...omium.org>,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v3 1/7] security: rename security_kernel_read_file() hook
On Thu, 2018-05-24 at 15:49 -0500, Eric W. Biederman wrote:
Thank you for the sample code below. It needs to be broken up into
proper patches, with some changes, but it is a good start.
Mimi
> diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
> index 358354148dec..04536ff81bd2 100644
> --- a/drivers/base/firmware_loader/fallback.c
> +++ b/drivers/base/firmware_loader/fallback.c
> @@ -294,9 +294,7 @@ static ssize_t firmware_loading_store(struct device *dev,
> dev_err(dev, "%s: map pages failed\n",
> __func__);
> else
> - rc = security_kernel_post_read_file(NULL,
> - fw_priv->data, fw_priv->size,
> - READING_FIRMWARE);
> + rc = security_kernel_arg(KARG_FIRMWARE);
>
> /*
> * Same logic as fw_load_abort, only the DONE bit
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 0e4647e0eb60..9fb42736ba29 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -11,6 +11,7 @@
> #define _LINUX_IMA_H
>
> #include <linux/fs.h>
> +#include <linux/security.h>
> #include <linux/kexec.h>
> struct linux_binprm;
>
> @@ -19,7 +20,7 @@ extern int ima_bprm_check(struct linux_binprm *bprm);
> extern int ima_file_check(struct file *file, int mask, int opened);
> extern void ima_file_free(struct file *file);
> extern int ima_file_mmap(struct file *file, unsigned long prot);
> -extern int ima_read_file(struct file *file, enum kernel_read_file_id id);
> +extern int ima_kernel_arg(enum kernel_arg_id id);
> extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
> enum kernel_read_file_id id);
> extern void ima_post_path_mknod(struct dentry *dentry);
> @@ -49,7 +50,7 @@ static inline int ima_file_mmap(struct file *file, unsigned long prot)
> return 0;
> }
>
> -static inline int ima_read_file(struct file *file, enum kernel_read_file_id id)
> +static inline int ima_kernel_arg(enum kernel_arg_id id)
> {
> return 0;
> }
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 9d0b286f3dba..7f8bc3030784 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -576,6 +576,10 @@
> * userspace to load a kernel module with the given name.
> * @kmod_name name of the module requested by the kernel
> * Return 0 if successful.
> + * @kernel_arg:
> + * Use a syscall argument
> + * @id kernel argument identifier
> + * Return 0 if permission is granted.
> * @kernel_read_file:
> * Read a file specified by userspace.
> * @file contains the file structure pointing to the file being read
> @@ -1577,6 +1581,7 @@ union security_list_options {
> int (*kernel_act_as)(struct cred *new, u32 secid);
> int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
> int (*kernel_module_request)(char *kmod_name);
> + int (*kernel_arg)(enum kernel_arg_id id);
> int (*kernel_read_file)(struct file *file, enum kernel_read_file_id id);
> int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size,
> enum kernel_read_file_id id);
> @@ -1866,6 +1871,7 @@ struct security_hook_heads {
> struct hlist_head cred_getsecid;
> struct hlist_head kernel_act_as;
> struct hlist_head kernel_create_files_as;
> + struct hlist_head kernel_arg;
> struct hlist_head kernel_read_file;
> struct hlist_head kernel_post_read_file;
> struct hlist_head kernel_module_request;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 200920f521a1..6cf1bd87f041 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -159,6 +159,32 @@ extern int mmap_min_addr_handler(struct ctl_table *table, int write,
> typedef int (*initxattrs) (struct inode *inode,
> const struct xattr *xattr_array, void *fs_data);
>
> +#define __kernel_arg_id(id) \
> + id(UNKNOWN, unknown) \
> + id(FIRMWARE, firmware) \
> + id(MODULE, kernel-module) \
> + id(MAX_ID, )
> +
> +#define __karg_enumify(ENUM, dummy) KARG_ ## ENUM,
> +#define __karg_stringify(dummy, str) #str,
> +
> +enum kernel_arg_id {
> + __kernel_arg_id(__karg_enumify)
> +};
> +
> +static const char * const kernel_arg_str[] = {
> + __kernel_arg_id(__karg_stringify)
> +};
> +
> +static inline const char *kernel_arg_id_str(enum kernel_arg_id id)
> +{
> + if ((unsigned)id >= KARG_MAX_ID)
> + return kernel_arg_str[KARG_UNKNOWN];
> +
> + return kernel_arg_str[id];
> +}
> +
> +
> #ifdef CONFIG_SECURITY
>
> struct security_mnt_opts {
> @@ -326,6 +352,7 @@ void security_cred_getsecid(const struct cred *c, u32 *secid);
> int security_kernel_act_as(struct cred *new, u32 secid);
> int security_kernel_create_files_as(struct cred *new, struct inode *inode);
> int security_kernel_module_request(char *kmod_name);
> +int security_kernel_arg(enum kernel_arg_id id);
> int security_kernel_read_file(struct file *file, enum kernel_read_file_id id);
> int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
> enum kernel_read_file_id id);
> @@ -923,6 +950,11 @@ static inline int security_kernel_module_request(char *kmod_name)
> return 0;
> }
>
> +static inline int security_kernel_arg(enum kernel_arg_id id)
> +{
> + return 0;
> +}
> +
> static inline int security_kernel_read_file(struct file *file,
> enum kernel_read_file_id id)
> {
> diff --git a/kernel/module.c b/kernel/module.c
> index ce8066b88178..03a1dd21ad4a 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2879,7 +2879,7 @@ static int copy_module_from_user(const void __user *umod, unsigned long len,
> if (info->len < sizeof(*(info->hdr)))
> return -ENOEXEC;
>
> - err = security_kernel_read_file(NULL, READING_MODULE);
> + err = security_kernel_arg(KARG_MODULE);
> if (err)
> return err;
>
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 74d0bd7e76d7..d51a8ca97238 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -421,32 +421,6 @@ void ima_post_path_mknod(struct dentry *dentry)
> iint->flags |= IMA_NEW_FILE;
> }
>
> -/**
> - * ima_read_file - pre-measure/appraise hook decision based on policy
> - * @file: pointer to the file to be measured/appraised/audit
> - * @read_id: caller identifier
> - *
> - * Permit reading a file based on policy. The policy rules are written
> - * in terms of the policy identifier. Appraising the integrity of
> - * a file requires a file descriptor.
> - *
> - * For permission return 0, otherwise return -EACCES.
> - */
> -int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
> -{
> - bool sig_enforce = is_module_sig_enforced();
> -
> - if (!file && read_id == READING_MODULE) {
> - if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
> - (ima_appraise & IMA_APPRAISE_ENFORCE)) {
> - pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
> - return -EACCES; /* INTEGRITY_UNKNOWN */
> - }
> - return 0; /* We rely on module signature checking */
> - }
> - return 0;
> -}
> -
> static int read_idmap[READING_MAX_ID] = {
> [READING_FIRMWARE] = FIRMWARE_CHECK,
> [READING_MODULE] = MODULE_CHECK,
> @@ -474,21 +448,7 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> enum ima_hooks func;
> u32 secid;
>
> - if (!file && read_id == READING_FIRMWARE) {
> - if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
> - (ima_appraise & IMA_APPRAISE_ENFORCE))
> - return -EACCES; /* INTEGRITY_UNKNOWN */
> - return 0;
> - }
> -
> - if (!file && read_id == READING_MODULE) /* MODULE_SIG_FORCE enabled */
> - return 0;
> -
> - /* permit signed certs */
> - if (!file && read_id == READING_X509_CERTIFICATE)
> - return 0;
> -
> - if (!file || !buf || size == 0) { /* should never happen */
> + if (!buf || size == 0) { /* should never happen */
> if (ima_appraise & IMA_APPRAISE_ENFORCE)
> return -EACCES;
> return 0;
> @@ -500,6 +460,40 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> MAY_READ, func, 0);
> }
>
> +/**
> + * ima_kernel_arg - pre-measure/appraise hook decision based on policy
> + * @id: caller identifier
> + *
> + * Permit using an argument to a syscall based on policy. The policy
> + * rules are written in terms of the policy identifier.
> + *
> + * For permission return 0, otherwise return -EACCES.
> + */
> +int ima_kernel_arg(enum kernel_arg_id id)
> +{
> + if (id == KARG_MODULE) {
> + bool sig_enforce = is_module_sig_enforced();
> + if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
> + (ima_appraise & IMA_APPRAISE_ENFORCE)) {
> + pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
> + return -EACCES; /* INTEGRITY_UNKNOWN */
> + }
> + return 0; /* We rely on module signature checking */
> + }
> + else if (id == KARG_FIRMWARE) {
> + if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
> + (ima_appraise & IMA_APPRAISE_ENFORCE))
> + return -EACCES; /* INTEGRITY_UNKNOWN */
> + return 0;
> + }
> + else {
> + if (ima_appraise & IMA_APPRAISE_ENFORCE)
> + return -EACCES;
> + return 0;
> + }
> + return 0;
> +}
> +
> static int __init init_ima(void)
> {
> int error;
> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
> index 5fa191252c8f..f5333e5abac9 100644
> --- a/security/loadpin/loadpin.c
> +++ b/security/loadpin/loadpin.c
> @@ -121,23 +121,24 @@ static void loadpin_sb_free_security(struct super_block *mnt_sb)
> }
> }
>
> -static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
> +static int loadpin_read_data(enum kernel_read_data_id id)
> {
> - struct super_block *load_root;
> - const char *origin = kernel_read_file_id_str(id);
> + const char *origin = kernel_arg_id_str(id);
>
> /* This handles the older init_module API that has a NULL file. */
> - if (!file) {
> - if (!enabled) {
> - report_load(origin, NULL, "old-api-pinning-ignored");
> - return 0;
> - }
> -
> - report_load(origin, NULL, "old-api-denied");
> - return -EPERM;
> + if (!enabled) {
> + report_load(origin, NULL, "old-api-pinning-ignored");
> + return 0;
> }
>
> - load_root = file->f_path.mnt->mnt_sb;
> + report_load(origin, NULL, "old-api-denied");
> + return -EPERM;
> +}
> +
> +static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
> +{
> + struct super_block *load_root;
> + const char *origin = kernel_read_file_id_str(id);
>
> /* First loaded module/firmware defines the root for all others. */
> spin_lock(&pinned_root_spinlock);
> @@ -175,6 +176,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
>
> static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
> + LSM_HOOK_INIT(kernel_read_data, loadpin_read_data),
> LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
> };
>
> diff --git a/security/security.c b/security/security.c
> index 7bc2fde023a7..9b5f43c24ee2 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1033,14 +1033,19 @@ int security_kernel_module_request(char *kmod_name)
> return call_int_hook(kernel_module_request, 0, kmod_name);
> }
>
> -int security_kernel_read_file(struct file *file, enum kernel_read_file_id id)
> +int security_kernel_arg(enum kernel_arg_id id)
> {
> int ret;
>
> - ret = call_int_hook(kernel_read_file, 0, file, id);
> - if (ret)
> - return ret;
> - return ima_read_file(file, id);
> + ret = call_int_hook(kernel_arg, 0, id);
> + if (!ret)
> + ret = ima_kernel_arg(id);
> + return ret;
> +}
> +
> +int security_kernel_read_file(struct file *file, enum kernel_read_file_id id)
> +{
> + return call_int_hook(kernel_read_file, 0, file, id);
> }
> EXPORT_SYMBOL_GPL(security_kernel_read_file);
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 4cafe6a19167..76843099fed6 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -4010,6 +4010,15 @@ static int selinux_kernel_module_request(char *kmod_name)
> SYSTEM__MODULE_REQUEST, &ad);
> }
>
> +static int selinux_kernel_module_arg(void)
> +{
> + /* init_module */
> + u32 sid = current_sid();
> + return avc_has_perm(&selinux_state,
> + sid, sid, SECCLASS_SYSTEM,
> + SYSTEM__MODULE_LOAD, NULL);
> +}
> +
> static int selinux_kernel_module_from_file(struct file *file)
> {
> struct common_audit_data ad;
> @@ -4018,12 +4027,6 @@ static int selinux_kernel_module_from_file(struct file *file)
> u32 sid = current_sid();
> int rc;
>
> - /* init_module */
> - if (file == NULL)
> - return avc_has_perm(&selinux_state,
> - sid, sid, SECCLASS_SYSTEM,
> - SYSTEM__MODULE_LOAD, NULL);
> -
> /* finit_module */
>
> ad.type = LSM_AUDIT_DATA_FILE;
> @@ -4043,6 +4046,20 @@ static int selinux_kernel_module_from_file(struct file *file)
> SYSTEM__MODULE_LOAD, &ad);
> }
>
> +static int selinux_kernel_arg(enum kernel_arg_id id)
> +{
> + int rc = 0;
> +
> + switch (id) {
> + case KARG_MODULE:
> + rc = selinux_kernel_module_arg();
> + break;
> + default:
> + break;
> + }
> + return rc;
> +}
> +
> static int selinux_kernel_read_file(struct file *file,
> enum kernel_read_file_id id)
> {
> @@ -6938,6 +6955,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as),
> LSM_HOOK_INIT(kernel_create_files_as, selinux_kernel_create_files_as),
> LSM_HOOK_INIT(kernel_module_request, selinux_kernel_module_request),
> + LSM_HOOK_INIT(kernel_arg, selinux_kernel_arg),
> LSM_HOOK_INIT(kernel_read_file, selinux_kernel_read_file),
> LSM_HOOK_INIT(task_setpgid, selinux_task_setpgid),
> LSM_HOOK_INIT(task_getpgid, selinux_task_getpgid),
>
> --
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