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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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#define pr_fmt(fmt) "LoadPin: " fmt
#include <linux/module.h>#include <linux/fs.h>#include <linux/hex.h>#include <linux/kernel_read_file.h>#include <linux/lsm_hooks.h>#include <linux/mount.h>#include <linux/blkdev.h>#include <linux/path.h>#include <linux/sched.h> /* current */#include <linux/string_helpers.h>#include <linux/dm-verity-loadpin.h>#include <uapi/linux/loadpin.h>#include <uapi/linux/lsm.h>
#define VERITY_DIGEST_FILE_HEADER "# LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS"
static void report_load(const char *origin, struct file *file, char *operation){ char *cmdline, *pathname;
pathname = kstrdup_quotable_file(file, GFP_KERNEL); cmdline = kstrdup_quotable_cmdline(current, GFP_KERNEL);
pr_notice("%s %s obj=%s%s%s pid=%d cmdline=%s%s%s\n", origin, operation, (pathname && pathname[0] != '<') ? "\"" : "", pathname, (pathname && pathname[0] != '<') ? "\"" : "", task_pid_nr(current), cmdline ? "\"" : "", cmdline, cmdline ? "\"" : "");
kfree(cmdline); kfree(pathname);}
static int enforce = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCE);static char *exclude_read_files[READING_MAX_ID];static int ignore_read_file_id[READING_MAX_ID] __ro_after_init;static struct super_block *pinned_root;static DEFINE_SPINLOCK(pinned_root_spinlock);#ifdef CONFIG_SECURITY_LOADPIN_VERITYstatic bool deny_reading_verity_digests;#endif
// initialized to falsestatic bool loadpin_root_writable;#ifdef CONFIG_SYSCTL
static int proc_handler_loadpin(const struct ctl_table *table, int dir, void *buffer, size_t *lenp, loff_t *ppos){ if (!loadpin_root_writable && SYSCTL_USER_TO_KERN(dir)) return -EINVAL; return proc_dointvec_minmax(table, dir, buffer, lenp, ppos);}
static const struct ctl_table loadpin_sysctl_table[] = { { .procname = "enforce", .data = &enforce, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_handler_loadpin, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, },};#endif
static void report_writable(struct super_block *mnt_sb, bool writable){ if (mnt_sb->s_bdev) { pr_info("%pg (%u:%u): %s\n", mnt_sb->s_bdev, MAJOR(mnt_sb->s_bdev->bd_dev), MINOR(mnt_sb->s_bdev->bd_dev), writable ? "writable" : "read-only"); } else pr_info("mnt_sb lacks block device, treating as: writable\n");
if (!writable) pr_info("load pinning engaged.\n");}
/* * This must be called after early kernel init, since then the rootdev * is available. */static bool sb_is_writable(struct super_block *mnt_sb){ bool writable = true;
if (mnt_sb->s_bdev) writable = !bdev_read_only(mnt_sb->s_bdev);
return writable;}
static void loadpin_sb_free_security(struct super_block *mnt_sb){ /* * When unmounting the filesystem we were using for load * pinning, we acknowledge the superblock release, but make sure * no other modules or firmware can be loaded when we are in * enforcing mode. Otherwise, allow the root to be reestablished. */ if (!IS_ERR_OR_NULL(pinned_root) && mnt_sb == pinned_root) { if (enforce) { pinned_root = ERR_PTR(-EIO); pr_info("umount pinned fs: refusing further loads\n"); } else { pinned_root = NULL; } }}
static int loadpin_check(struct file *file, enum kernel_read_file_id id){ struct super_block *load_root; const char *origin = kernel_read_file_id_str(id); bool first_root_pin = false;
/* If the file id is excluded, ignore the pinning. */ if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) && ignore_read_file_id[id]) { report_load(origin, file, "pinning-excluded"); return 0; }
/* This handles the older init_module API that has a NULL file. */ if (!file) { if (!enforce) { report_load(origin, NULL, "old-api-pinning-ignored"); return 0; }
report_load(origin, NULL, "old-api-denied"); return -EPERM; }
load_root = file->f_path.mnt->mnt_sb;
/* First loaded module/firmware defines the root for all others. */ spin_lock(&pinned_root_spinlock); /* * pinned_root is only NULL at startup or when the pinned root has * been unmounted while we are not in enforcing mode. Otherwise, it * is either a valid reference, or an ERR_PTR. */ if (!pinned_root) { pinned_root = load_root; first_root_pin = true; } spin_unlock(&pinned_root_spinlock);
if (first_root_pin) { loadpin_root_writable = sb_is_writable(pinned_root); report_writable(pinned_root, loadpin_root_writable); report_load(origin, file, "pinned"); }
if (IS_ERR_OR_NULL(pinned_root) || ((load_root != pinned_root) && !dm_verity_loadpin_is_bdev_trusted(load_root->s_bdev))) { if (unlikely(!enforce)) { report_load(origin, file, "pinning-ignored"); return 0; }
report_load(origin, file, "denied"); return -EPERM; }
return 0;}
static int loadpin_read_file(struct file *file, enum kernel_read_file_id id, bool contents){ /* * LoadPin only cares about the _origin_ of a file, not its * contents, so we can ignore the "are full contents available" * argument here. */ return loadpin_check(file, id);}
static int loadpin_load_data(enum kernel_load_data_id id, bool contents){ /* * LoadPin only cares about the _origin_ of a file, not its * contents, so a NULL file is passed, and we can ignore the * state of "contents". */ return loadpin_check(NULL, (enum kernel_read_file_id) id);}
static const struct lsm_id loadpin_lsmid = { .name = "loadpin", .id = LSM_ID_LOADPIN,};
static struct security_hook_list loadpin_hooks[] __ro_after_init = { LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security), LSM_HOOK_INIT(kernel_read_file, loadpin_read_file), LSM_HOOK_INIT(kernel_load_data, loadpin_load_data),};
static void __init parse_exclude(void){ int i, j; char *cur;
/* * Make sure all the arrays stay within expected sizes. This * is slightly weird because kernel_read_file_str[] includes * READING_MAX_ID, which isn't actually meaningful here. */ BUILD_BUG_ON(ARRAY_SIZE(exclude_read_files) != ARRAY_SIZE(ignore_read_file_id)); BUILD_BUG_ON(ARRAY_SIZE(kernel_read_file_str) < ARRAY_SIZE(ignore_read_file_id));
for (i = 0; i < ARRAY_SIZE(exclude_read_files); i++) { cur = exclude_read_files[i]; if (!cur) break; if (*cur == '\0') continue;
for (j = 0; j < ARRAY_SIZE(ignore_read_file_id); j++) { if (strcmp(cur, kernel_read_file_str[j]) == 0) { pr_info("excluding: %s\n", kernel_read_file_str[j]); ignore_read_file_id[j] = 1; /* * Can not break, because one read_file_str * may map to more than on read_file_id. */ } } }}
static int __init loadpin_init(void){ pr_info("ready to pin (currently %senforcing)\n", enforce ? "" : "not "); parse_exclude();#ifdef CONFIG_SYSCTL if (!register_sysctl("kernel/loadpin", loadpin_sysctl_table)) pr_notice("sysctl registration failed!\n");#endif security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), &loadpin_lsmid);
return 0;}
#ifdef CONFIG_SECURITY_LOADPIN_VERITY
enum loadpin_securityfs_interface_index { LOADPIN_DM_VERITY,};
static int read_trusted_verity_root_digests(unsigned int fd){ void *data; int rc; char *p, *d;
if (deny_reading_verity_digests) return -EPERM;
/* The list of trusted root digests can only be set up once */ if (!list_empty(&dm_verity_loadpin_trusted_root_digests)) return -EPERM;
CLASS(fd, f)(fd); if (fd_empty(f)) return -EINVAL;
data = kzalloc(SZ_4K, GFP_KERNEL); if (!data) { rc = -ENOMEM; goto err; }
rc = kernel_read_file(fd_file(f), 0, (void **)&data, SZ_4K - 1, NULL, READING_POLICY); if (rc < 0) goto err;
p = data; p[rc] = '\0'; p = strim(p);
p = strim(data); while ((d = strsep(&p, "\n")) != NULL) { int len; struct dm_verity_loadpin_trusted_root_digest *trd;
if (d == data) { /* first line, validate header */ if (strcmp(d, VERITY_DIGEST_FILE_HEADER)) { rc = -EPROTO; goto err; }
continue; }
len = strlen(d);
if (len % 2) { rc = -EPROTO; goto err; }
len /= 2;
trd = kzalloc_flex(*trd, data, len); if (!trd) { rc = -ENOMEM; goto err; } trd->len = len;
if (hex2bin(trd->data, d, len)) { kfree(trd); rc = -EPROTO; goto err; }
list_add_tail(&trd->node, &dm_verity_loadpin_trusted_root_digests); }
if (list_empty(&dm_verity_loadpin_trusted_root_digests)) { rc = -EPROTO; goto err; }
kfree(data);
return 0;
err: kfree(data);
/* any failure in loading/parsing invalidates the entire list */ { struct dm_verity_loadpin_trusted_root_digest *trd, *tmp;
list_for_each_entry_safe(trd, tmp, &dm_verity_loadpin_trusted_root_digests, node) { list_del(&trd->node); kfree(trd); } }
/* disallow further attempts after reading a corrupt/invalid file */ deny_reading_verity_digests = true;
return rc;}
/******************************** securityfs ********************************/
static long dm_verity_ioctl(struct file *filp, unsigned int cmd, unsigned long arg){ void __user *uarg = (void __user *)arg; unsigned int fd;
switch (cmd) { case LOADPIN_IOC_SET_TRUSTED_VERITY_DIGESTS: if (copy_from_user(&fd, uarg, sizeof(fd))) return -EFAULT;
return read_trusted_verity_root_digests(fd);
default: return -EINVAL; }}
static const struct file_operations loadpin_dm_verity_ops = { .unlocked_ioctl = dm_verity_ioctl, .compat_ioctl = compat_ptr_ioctl,};
/** * init_loadpin_securityfs - create the securityfs directory for LoadPin * * We can not put this method normally under the loadpin_init() code path since * the security subsystem gets initialized before the vfs caches. * * Returns 0 if the securityfs directory creation was successful. */static int __init init_loadpin_securityfs(void){ struct dentry *loadpin_dir, *dentry;
loadpin_dir = securityfs_create_dir("loadpin", NULL); if (IS_ERR(loadpin_dir)) { pr_err("LoadPin: could not create securityfs dir: %ld\n", PTR_ERR(loadpin_dir)); return PTR_ERR(loadpin_dir); }
dentry = securityfs_create_file("dm-verity", 0600, loadpin_dir, (void *)LOADPIN_DM_VERITY, &loadpin_dm_verity_ops); if (IS_ERR(dentry)) { pr_err("LoadPin: could not create securityfs entry 'dm-verity': %ld\n", PTR_ERR(dentry)); return PTR_ERR(dentry); }
return 0;}
#endif /* CONFIG_SECURITY_LOADPIN_VERITY */
DEFINE_LSM(loadpin) = { .id = &loadpin_lsmid, .init = loadpin_init,#ifdef CONFIG_SECURITY_LOADPIN_VERITY .initcall_fs = init_loadpin_securityfs,#endif /* CONFIG_SECURITY_LOADPIN_VERITY */};
/* Should not be mutable after boot, so not listed in sysfs (perm == 0). */module_param(enforce, int, 0);MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning");module_param_array_named(exclude, exclude_read_files, charp, NULL, 0);MODULE_PARM_DESC(exclude, "Exclude pinning specific read file types");