Introduce <securityfs>/integrity/diglim/digest_list_add, which can be used to upload a digest list and add the digests to the hash table; passed data are interpreted as file path if the first byte is / or as the digest list itself otherwise.
diglim_ima_get_info() is called to retrieve from IMA the digest of the passed digest list (file or buffer), and the actions performed (measure/ appraise/appraise with signature).
Also introduce <securityfs>/integrity/diglim/digest_list_del, which can be used to upload a digest list and delete the digests from the hash table; data are interpreted in the same way as described for digest_list_add.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- .../security/diglim/implementation.rst | 9 + MAINTAINERS | 1 + include/linux/kernel_read_file.h | 1 + security/integrity/diglim/Makefile | 2 +- security/integrity/diglim/diglim.h | 2 + security/integrity/diglim/fs.c | 276 ++++++++++++++++++ 6 files changed, 290 insertions(+), 1 deletion(-) create mode 100644 security/integrity/diglim/fs.c
diff --git a/Documentation/security/diglim/implementation.rst b/Documentation/security/diglim/implementation.rst index 626af0d245ef..f7b48c093f39 100644 --- a/Documentation/security/diglim/implementation.rst +++ b/Documentation/security/diglim/implementation.rst @@ -217,3 +217,12 @@ back when one of the steps fails.
#. digest_list_parse() deletes the struct digest_list_item on unsuccessful add or successful delete. + + +Interfaces +---------- + +This section introduces the interfaces in +``<securityfs>/integrity/diglim`` necessary to interact with DIGLIM. + +.. kernel-doc:: security/integrity/diglim/fs.c diff --git a/MAINTAINERS b/MAINTAINERS index f10690dda734..826f628f4fab 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5514,6 +5514,7 @@ F: Documentation/security/diglim/introduction.rst F: include/linux/diglim.h F: include/uapi/linux/diglim.h F: security/integrity/diglim/diglim.h +F: security/integrity/diglim/fs.c F: security/integrity/diglim/ima.c F: security/integrity/diglim/methods.c F: security/integrity/diglim/parser.c diff --git a/include/linux/kernel_read_file.h b/include/linux/kernel_read_file.h index 575ffa1031d3..636ecdfdc616 100644 --- a/include/linux/kernel_read_file.h +++ b/include/linux/kernel_read_file.h @@ -14,6 +14,7 @@ id(KEXEC_INITRAMFS, kexec-initramfs) \ id(POLICY, security-policy) \ id(X509_CERTIFICATE, x509-certificate) \ + id(DIGEST_LIST, digest-list) \ id(MAX_ID, )
#define __fid_enumify(ENUM, dummy) READING_ ## ENUM, diff --git a/security/integrity/diglim/Makefile b/security/integrity/diglim/Makefile index 880dc5300792..5cb1a8bfa0fc 100644 --- a/security/integrity/diglim/Makefile +++ b/security/integrity/diglim/Makefile @@ -5,4 +5,4 @@
obj-$(CONFIG_DIGLIM) += diglim.o
-diglim-y := methods.o parser.o ima.o +diglim-y := methods.o parser.o ima.o fs.o diff --git a/security/integrity/diglim/diglim.h b/security/integrity/diglim/diglim.h index ebe8936520b5..c597c2e7a52a 100644 --- a/security/integrity/diglim/diglim.h +++ b/security/integrity/diglim/diglim.h @@ -227,4 +227,6 @@ int digest_list_parse(loff_t size, void *buf, enum ops op, u8 actions, int diglim_ima_get_info(struct file *file, u8 *buffer, size_t buffer_len, char *event_name, u8 *digest, size_t digest_len, enum hash_algo *algo, u8 *actions); + +ssize_t digest_list_read(struct path *root, char *path, enum ops op); #endif /*__DIGLIM_INTERNAL_H*/ diff --git a/security/integrity/diglim/fs.c b/security/integrity/diglim/fs.c new file mode 100644 index 000000000000..5698afd2d18a --- /dev/null +++ b/security/integrity/diglim/fs.c @@ -0,0 +1,276 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2005,2006,2007,2008 IBM Corporation + * Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu roberto.sassu@huawei.com + * + * Functions for the interfaces exposed in securityfs. + */ + +#include <linux/fcntl.h> +#include <linux/kernel_read_file.h> +#include <linux/module_signature.h> +#include <linux/slab.h> +#include <linux/init.h> +#include <linux/seq_file.h> +#include <linux/rculist.h> +#include <linux/rcupdate.h> +#include <linux/parser.h> +#include <linux/vmalloc.h> +#include <linux/namei.h> +#include <linux/ima.h> + +#include "diglim.h" + +#define MAX_DIGEST_LIST_SIZE (64 * 1024 * 1024 - 1) + +static struct dentry *diglim_dir; +/** + * DOC: digest_list_add + * + * digest_list_add can be used to upload a digest list and add the digests + * to the hash table; passed data are interpreted as file path if the first + * byte is ``/`` or as the digest list itself otherwise. + * + * diglim_ima_get_info() is called to retrieve from IMA the digest of the passed + * digest list (file or buffer), and the actions performed (measure/appraise/ + * appraise with signature). + */ +static struct dentry *digest_list_add_dentry; +/** + * DOC: digest_list_del + * + * digest_list_del can be used to upload a digest list and delete the + * digests from the hash table; data are interpreted in the same way as + * described for digest_list_add. + */ +static struct dentry *digest_list_del_dentry; +char digest_list_label[NAME_MAX + 1]; + +/* + * check_modsig: detect appended signature + */ +static int check_modsig(u8 *buf, size_t buf_len) +{ + const size_t marker_len = strlen(MODULE_SIG_STRING); + const struct module_signature *sig; + size_t sig_len; + const void *p; + + if (buf_len <= marker_len + sizeof(*sig)) + return -ENOENT; + + p = buf + buf_len - marker_len; + if (memcmp(p, MODULE_SIG_STRING, marker_len)) + return -ENOENT; + + sig = (const struct module_signature *)(p - sizeof(*sig)); + sig_len = be32_to_cpu(sig->sig_len); + return marker_len + sig_len + sizeof(*sig); +} + +/* + * digest_list_read: read and parse the digest list from the path + */ +ssize_t digest_list_read(struct path *root, char *path, enum ops op) +{ + void *data = NULL; + char *datap; + size_t size; + u8 actions = 0; + struct file *file; + char event_name[NAME_MAX + 9 + 1]; + u8 digest[IMA_MAX_DIGEST_SIZE] = { 0 }; + enum hash_algo algo; + int rc, pathlen = strlen(path); + + /* Remove \n. */ + datap = path; + strsep(&datap, "\n"); + + if (root) + file = file_open_root(root, path, O_RDONLY, 0); + else + file = filp_open(path, O_RDONLY, 0); + if (IS_ERR(file)) { + pr_err("unable to open file: %s (%ld)", path, PTR_ERR(file)); + return PTR_ERR(file); + } + + /* Deny writes to the file to obtain stable information from IMA. */ + rc = deny_write_access(file); + if (rc < 0) { + pr_err("unable to deny write access to file: %s (%d)", path, + rc); + goto out; + } + + rc = kernel_read_file(file, 0, &data, INT_MAX, NULL, + READING_DIGEST_LIST); + if (rc < 0) { + pr_err("unable to read file: %s (%d)", path, rc); + goto out_allow_write; + } + + size = rc; + rc = check_modsig(data, size); + if (rc > 0) + size -= rc; + + snprintf(event_name, sizeof(event_name), "%s_file_%s", + op == DIGEST_LIST_ADD ? "add" : "del", + file_dentry(file)->d_name.name); + + rc = diglim_ima_get_info(file, data, size, event_name, digest, + sizeof(digest), &algo, &actions); + if (rc < 0) { + pr_err("unable to retrieve IMA info for %s (%d)\n", path, rc); + goto out_vfree; + } + + rc = digest_list_parse(size, data, op, actions, digest, algo, ""); + if (rc < 0 && rc != -EEXIST) + pr_err("unable to upload digest list %s (%d)\n", path, rc); +out_vfree: + vfree(data); +out_allow_write: + allow_write_access(file); +out: + fput(file); + + if (rc < 0) + return rc; + + return pathlen; +} + +/* + * digest_list_write: write the digest list path or the digest list itself + */ +static ssize_t digest_list_write(struct file *file, const char __user *buf, + size_t datalen, loff_t *ppos) +{ + char *data; + char *digest_list_label_ptr; + ssize_t result; + enum ops op = DIGEST_LIST_ADD; + struct dentry *dentry = file_dentry(file); + u8 digest[IMA_MAX_DIGEST_SIZE]; + char event_name[NAME_MAX + 11 + 1]; + enum hash_algo algo; + u8 actions = 0; + + /* No partial writes. */ + result = -EINVAL; + if (*ppos != 0) + goto out; + + result = -EFBIG; + if (datalen > MAX_DIGEST_LIST_SIZE) + goto out; + + data = memdup_user_nul(buf, datalen); + if (IS_ERR(data)) { + result = PTR_ERR(data); + goto out; + } + + if (dentry == digest_list_del_dentry) + op = DIGEST_LIST_DEL; + + result = -EPERM; + + if (data[0] == '/') { + result = digest_list_read(NULL, data, op); + } else { + /* Remove \n. */ + digest_list_label_ptr = digest_list_label; + strsep(&digest_list_label_ptr, "\n"); + + snprintf(event_name, sizeof(event_name), "%s_buffer_%s", + op == DIGEST_LIST_ADD ? "add" : "del", + digest_list_label); + + result = diglim_ima_get_info(NULL, data, datalen, event_name, + digest, sizeof(digest), &algo, + &actions); + if (result < 0) { + pr_err("unable to retrieve IMA info for buffer (%ld)\n", + result); + goto out_kfree; + } + + memset(digest_list_label, 0, sizeof(digest_list_label)); + + result = digest_list_parse(datalen, data, op, actions, digest, + algo, ""); + if (result < 0 && result != -EEXIST) + pr_err("unable to upload generated digest list\n"); + } +out_kfree: + kfree(data); +out: + return result; +} + +static unsigned long flags; + +/* + * digest_list_open: sequentialize access to the add/del files + */ +static int digest_list_open(struct inode *inode, struct file *filp) +{ + if ((filp->f_flags & O_ACCMODE) != O_WRONLY) + return -EACCES; + + if (test_and_set_bit(0, &flags)) + return -EBUSY; + + return 0; +} + +/* + * digest_list_release - release the add/del files + */ +static int digest_list_release(struct inode *inode, struct file *file) +{ + clear_bit(0, &flags); + return 0; +} + +static const struct file_operations digest_list_upload_ops = { + .open = digest_list_open, + .write = digest_list_write, + .read = seq_read, + .release = digest_list_release, + .llseek = generic_file_llseek, +}; + +static int __init diglim_fs_init(void) +{ + diglim_dir = securityfs_create_dir("diglim", integrity_dir); + if (IS_ERR(diglim_dir)) + return -1; + + digest_list_add_dentry = securityfs_create_file("digest_list_add", 0200, + diglim_dir, NULL, + &digest_list_upload_ops); + if (IS_ERR(digest_list_add_dentry)) + goto out; + + digest_list_del_dentry = securityfs_create_file("digest_list_del", 0200, + diglim_dir, NULL, + &digest_list_upload_ops); + if (IS_ERR(digest_list_del_dentry)) + goto out; + + return 0; +out: + securityfs_remove(digest_list_del_dentry); + securityfs_remove(digest_list_add_dentry); + securityfs_remove(diglim_dir); + return -1; +} + +late_initcall(diglim_fs_init);