1 /*
2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
3  *
4  * Authors:
5  * Mimi Zohar <zohar@us.ibm.com>
6  * Kylene Hall <kjhall@us.ibm.com>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation, version 2 of the License.
11  *
12  * File: ima_crypto.c
13  * 	Calculates md5/sha1 file hash, template hash, boot-aggreate hash
14  */
15 
16 #include <linux/kernel.h>
17 #include <linux/file.h>
18 #include <linux/crypto.h>
19 #include <linux/scatterlist.h>
20 #include <linux/err.h>
21 #include <linux/slab.h>
22 #include "ima.h"
23 
24 static int init_desc(struct hash_desc *desc)
25 {
26 	int rc;
27 
28 	desc->tfm = crypto_alloc_hash(ima_hash, 0, CRYPTO_ALG_ASYNC);
29 	if (IS_ERR(desc->tfm)) {
30 		pr_info("IMA: failed to load %s transform: %ld\n",
31 			ima_hash, PTR_ERR(desc->tfm));
32 		rc = PTR_ERR(desc->tfm);
33 		return rc;
34 	}
35 	desc->flags = 0;
36 	rc = crypto_hash_init(desc);
37 	if (rc)
38 		crypto_free_hash(desc->tfm);
39 	return rc;
40 }
41 
42 /*
43  * Calculate the MD5/SHA1 file digest
44  */
45 int ima_calc_hash(struct file *file, char *digest)
46 {
47 	struct hash_desc desc;
48 	struct scatterlist sg[1];
49 	loff_t i_size, offset = 0;
50 	char *rbuf;
51 	int rc;
52 
53 	rc = init_desc(&desc);
54 	if (rc != 0)
55 		return rc;
56 
57 	rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
58 	if (!rbuf) {
59 		rc = -ENOMEM;
60 		goto out;
61 	}
62 	i_size = i_size_read(file->f_dentry->d_inode);
63 	while (offset < i_size) {
64 		int rbuf_len;
65 
66 		rbuf_len = kernel_read(file, offset, rbuf, PAGE_SIZE);
67 		if (rbuf_len < 0) {
68 			rc = rbuf_len;
69 			break;
70 		}
71 		if (rbuf_len == 0)
72 			break;
73 		offset += rbuf_len;
74 		sg_init_one(sg, rbuf, rbuf_len);
75 
76 		rc = crypto_hash_update(&desc, sg, rbuf_len);
77 		if (rc)
78 			break;
79 	}
80 	kfree(rbuf);
81 	if (!rc)
82 		rc = crypto_hash_final(&desc, digest);
83 out:
84 	crypto_free_hash(desc.tfm);
85 	return rc;
86 }
87 
88 /*
89  * Calculate the hash of a given template
90  */
91 int ima_calc_template_hash(int template_len, void *template, char *digest)
92 {
93 	struct hash_desc desc;
94 	struct scatterlist sg[1];
95 	int rc;
96 
97 	rc = init_desc(&desc);
98 	if (rc != 0)
99 		return rc;
100 
101 	sg_init_one(sg, template, template_len);
102 	rc = crypto_hash_update(&desc, sg, template_len);
103 	if (!rc)
104 		rc = crypto_hash_final(&desc, digest);
105 	crypto_free_hash(desc.tfm);
106 	return rc;
107 }
108 
109 static void __init ima_pcrread(int idx, u8 *pcr)
110 {
111 	if (!ima_used_chip)
112 		return;
113 
114 	if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0)
115 		pr_err("IMA: Error Communicating to TPM chip\n");
116 }
117 
118 /*
119  * Calculate the boot aggregate hash
120  */
121 int __init ima_calc_boot_aggregate(char *digest)
122 {
123 	struct hash_desc desc;
124 	struct scatterlist sg;
125 	u8 pcr_i[IMA_DIGEST_SIZE];
126 	int rc, i;
127 
128 	rc = init_desc(&desc);
129 	if (rc != 0)
130 		return rc;
131 
132 	/* cumulative sha1 over tpm registers 0-7 */
133 	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
134 		ima_pcrread(i, pcr_i);
135 		/* now accumulate with current aggregate */
136 		sg_init_one(&sg, pcr_i, IMA_DIGEST_SIZE);
137 		rc = crypto_hash_update(&desc, &sg, IMA_DIGEST_SIZE);
138 	}
139 	if (!rc)
140 		crypto_hash_final(&desc, digest);
141 	crypto_free_hash(desc.tfm);
142 	return rc;
143 }
144