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152 lines
3.8 KiB
152 lines
3.8 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Verification of builtin signatures |
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* |
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* Copyright 2019 Google LLC |
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*/ |
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#include "fsverity_private.h" |
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#include <linux/cred.h> |
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#include <linux/key.h> |
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#include <linux/slab.h> |
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#include <linux/verification.h> |
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/* |
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* /proc/sys/fs/verity/require_signatures |
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* If 1, all verity files must have a valid builtin signature. |
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*/ |
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static int fsverity_require_signatures; |
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/* |
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* Keyring that contains the trusted X.509 certificates. |
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* |
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* Only root (kuid=0) can modify this. Also, root may use |
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* keyctl_restrict_keyring() to prevent any more additions. |
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*/ |
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static struct key *fsverity_keyring; |
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/** |
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* fsverity_verify_signature() - check a verity file's signature |
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* @vi: the file's fsverity_info |
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* @signature: the file's built-in signature |
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* @sig_size: size of signature in bytes, or 0 if no signature |
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* |
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* If the file includes a signature of its fs-verity file digest, verify it |
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* against the certificates in the fs-verity keyring. |
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* |
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* Return: 0 on success (signature valid or not required); -errno on failure |
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*/ |
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int fsverity_verify_signature(const struct fsverity_info *vi, |
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const u8 *signature, size_t sig_size) |
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{ |
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const struct inode *inode = vi->inode; |
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const struct fsverity_hash_alg *hash_alg = vi->tree_params.hash_alg; |
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struct fsverity_formatted_digest *d; |
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int err; |
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if (sig_size == 0) { |
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if (fsverity_require_signatures) { |
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fsverity_err(inode, |
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"require_signatures=1, rejecting unsigned file!"); |
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return -EPERM; |
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} |
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return 0; |
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} |
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d = kzalloc(sizeof(*d) + hash_alg->digest_size, GFP_KERNEL); |
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if (!d) |
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return -ENOMEM; |
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memcpy(d->magic, "FSVerity", 8); |
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d->digest_algorithm = cpu_to_le16(hash_alg - fsverity_hash_algs); |
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d->digest_size = cpu_to_le16(hash_alg->digest_size); |
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memcpy(d->digest, vi->file_digest, hash_alg->digest_size); |
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err = verify_pkcs7_signature(d, sizeof(*d) + hash_alg->digest_size, |
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signature, sig_size, fsverity_keyring, |
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VERIFYING_UNSPECIFIED_SIGNATURE, |
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NULL, NULL); |
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kfree(d); |
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if (err) { |
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if (err == -ENOKEY) |
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fsverity_err(inode, |
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"File's signing cert isn't in the fs-verity keyring"); |
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else if (err == -EKEYREJECTED) |
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fsverity_err(inode, "Incorrect file signature"); |
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else if (err == -EBADMSG) |
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fsverity_err(inode, "Malformed file signature"); |
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else |
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fsverity_err(inode, "Error %d verifying file signature", |
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err); |
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return err; |
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} |
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pr_debug("Valid signature for file digest %s:%*phN\n", |
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hash_alg->name, hash_alg->digest_size, vi->file_digest); |
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return 0; |
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} |
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#ifdef CONFIG_SYSCTL |
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static struct ctl_table_header *fsverity_sysctl_header; |
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static const struct ctl_path fsverity_sysctl_path[] = { |
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{ .procname = "fs", }, |
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{ .procname = "verity", }, |
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{ } |
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}; |
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static struct ctl_table fsverity_sysctl_table[] = { |
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{ |
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.procname = "require_signatures", |
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.data = &fsverity_require_signatures, |
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.maxlen = sizeof(int), |
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.mode = 0644, |
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.proc_handler = proc_dointvec_minmax, |
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.extra1 = SYSCTL_ZERO, |
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.extra2 = SYSCTL_ONE, |
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}, |
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{ } |
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}; |
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static int __init fsverity_sysctl_init(void) |
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{ |
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fsverity_sysctl_header = register_sysctl_paths(fsverity_sysctl_path, |
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fsverity_sysctl_table); |
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if (!fsverity_sysctl_header) { |
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pr_err("sysctl registration failed!\n"); |
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return -ENOMEM; |
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} |
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return 0; |
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} |
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#else /* !CONFIG_SYSCTL */ |
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static inline int __init fsverity_sysctl_init(void) |
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{ |
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return 0; |
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} |
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#endif /* !CONFIG_SYSCTL */ |
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int __init fsverity_init_signature(void) |
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{ |
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struct key *ring; |
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int err; |
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ring = keyring_alloc(".fs-verity", KUIDT_INIT(0), KGIDT_INIT(0), |
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current_cred(), KEY_POS_SEARCH | |
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KEY_USR_VIEW | KEY_USR_READ | KEY_USR_WRITE | |
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KEY_USR_SEARCH | KEY_USR_SETATTR, |
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KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); |
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if (IS_ERR(ring)) |
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return PTR_ERR(ring); |
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err = fsverity_sysctl_init(); |
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if (err) |
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goto err_put_ring; |
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fsverity_keyring = ring; |
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return 0; |
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err_put_ring: |
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key_put(ring); |
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return err; |
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}
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