This source file includes following definitions.
- fsverity_verify_signature
- fsverity_sysctl_init
- fsverity_sysctl_init
- fsverity_init_signature
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8 #include "fsverity_private.h"
9
10 #include <linux/cred.h>
11 #include <linux/key.h>
12 #include <linux/slab.h>
13 #include <linux/verification.h>
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15
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17
18
19 static int fsverity_require_signatures;
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26
27 static struct key *fsverity_keyring;
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36
37 int fsverity_verify_signature(const struct fsverity_info *vi,
38 const struct fsverity_descriptor *desc,
39 size_t desc_size)
40 {
41 const struct inode *inode = vi->inode;
42 const struct fsverity_hash_alg *hash_alg = vi->tree_params.hash_alg;
43 const u32 sig_size = le32_to_cpu(desc->sig_size);
44 struct fsverity_signed_digest *d;
45 int err;
46
47 if (sig_size == 0) {
48 if (fsverity_require_signatures) {
49 fsverity_err(inode,
50 "require_signatures=1, rejecting unsigned file!");
51 return -EPERM;
52 }
53 return 0;
54 }
55
56 if (sig_size > desc_size - sizeof(*desc)) {
57 fsverity_err(inode, "Signature overflows verity descriptor");
58 return -EBADMSG;
59 }
60
61 d = kzalloc(sizeof(*d) + hash_alg->digest_size, GFP_KERNEL);
62 if (!d)
63 return -ENOMEM;
64 memcpy(d->magic, "FSVerity", 8);
65 d->digest_algorithm = cpu_to_le16(hash_alg - fsverity_hash_algs);
66 d->digest_size = cpu_to_le16(hash_alg->digest_size);
67 memcpy(d->digest, vi->measurement, hash_alg->digest_size);
68
69 err = verify_pkcs7_signature(d, sizeof(*d) + hash_alg->digest_size,
70 desc->signature, sig_size,
71 fsverity_keyring,
72 VERIFYING_UNSPECIFIED_SIGNATURE,
73 NULL, NULL);
74 kfree(d);
75
76 if (err) {
77 if (err == -ENOKEY)
78 fsverity_err(inode,
79 "File's signing cert isn't in the fs-verity keyring");
80 else if (err == -EKEYREJECTED)
81 fsverity_err(inode, "Incorrect file signature");
82 else if (err == -EBADMSG)
83 fsverity_err(inode, "Malformed file signature");
84 else
85 fsverity_err(inode, "Error %d verifying file signature",
86 err);
87 return err;
88 }
89
90 pr_debug("Valid signature for file measurement %s:%*phN\n",
91 hash_alg->name, hash_alg->digest_size, vi->measurement);
92 return 0;
93 }
94
95 #ifdef CONFIG_SYSCTL
96 static struct ctl_table_header *fsverity_sysctl_header;
97
98 static const struct ctl_path fsverity_sysctl_path[] = {
99 { .procname = "fs", },
100 { .procname = "verity", },
101 { }
102 };
103
104 static struct ctl_table fsverity_sysctl_table[] = {
105 {
106 .procname = "require_signatures",
107 .data = &fsverity_require_signatures,
108 .maxlen = sizeof(int),
109 .mode = 0644,
110 .proc_handler = proc_dointvec_minmax,
111 .extra1 = SYSCTL_ZERO,
112 .extra2 = SYSCTL_ONE,
113 },
114 { }
115 };
116
117 static int __init fsverity_sysctl_init(void)
118 {
119 fsverity_sysctl_header = register_sysctl_paths(fsverity_sysctl_path,
120 fsverity_sysctl_table);
121 if (!fsverity_sysctl_header) {
122 pr_err("sysctl registration failed!\n");
123 return -ENOMEM;
124 }
125 return 0;
126 }
127 #else
128 static inline int __init fsverity_sysctl_init(void)
129 {
130 return 0;
131 }
132 #endif
133
134 int __init fsverity_init_signature(void)
135 {
136 struct key *ring;
137 int err;
138
139 ring = keyring_alloc(".fs-verity", KUIDT_INIT(0), KGIDT_INIT(0),
140 current_cred(), KEY_POS_SEARCH |
141 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_WRITE |
142 KEY_USR_SEARCH | KEY_USR_SETATTR,
143 KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
144 if (IS_ERR(ring))
145 return PTR_ERR(ring);
146
147 err = fsverity_sysctl_init();
148 if (err)
149 goto err_put_ring;
150
151 fsverity_keyring = ring;
152 return 0;
153
154 err_put_ring:
155 key_put(ring);
156 return err;
157 }