1 /* 2 * Copyright (c) 2013, Google Inc. 3 * 4 * SPDX-License-Identifier: GPL-2.0+ 5 */ 6 7 #ifndef USE_HOSTCC 8 #include <common.h> 9 #include <fdtdec.h> 10 #include <asm/types.h> 11 #include <asm/byteorder.h> 12 #include <linux/errno.h> 13 #include <asm/types.h> 14 #include <asm/unaligned.h> 15 #include <dm.h> 16 #else 17 #include "fdt_host.h" 18 #include "mkimage.h" 19 #include <fdt_support.h> 20 #endif 21 #include <u-boot/rsa-mod-exp.h> 22 #include <u-boot/rsa.h> 23 24 /* Default public exponent for backward compatibility */ 25 #define RSA_DEFAULT_PUBEXP 65537 26 27 /** 28 * rsa_verify_key() - Verify a signature against some data using RSA Key 29 * 30 * Verify a RSA PKCS1.5 signature against an expected hash using 31 * the RSA Key properties in prop structure. 32 * 33 * @prop: Specifies key 34 * @sig: Signature 35 * @sig_len: Number of bytes in signature 36 * @hash: Pointer to the expected hash 37 * @algo: Checksum algo structure having information on RSA padding etc. 38 * @return 0 if verified, -ve on error 39 */ 40 static int rsa_verify_key(struct key_prop *prop, const uint8_t *sig, 41 const uint32_t sig_len, const uint8_t *hash, 42 struct checksum_algo *algo) 43 { 44 const uint8_t *padding; 45 int pad_len; 46 int ret; 47 #if !defined(USE_HOSTCC) 48 struct udevice *mod_exp_dev; 49 #endif 50 51 if (!prop || !sig || !hash || !algo) 52 return -EIO; 53 54 if (sig_len != (prop->num_bits / 8)) { 55 debug("Signature is of incorrect length %d\n", sig_len); 56 return -EINVAL; 57 } 58 59 debug("Checksum algorithm: %s", algo->name); 60 61 /* Sanity check for stack size */ 62 if (sig_len > RSA_MAX_SIG_BITS / 8) { 63 debug("Signature length %u exceeds maximum %d\n", sig_len, 64 RSA_MAX_SIG_BITS / 8); 65 return -EINVAL; 66 } 67 68 uint8_t buf[sig_len]; 69 70 #if !defined(USE_HOSTCC) 71 ret = uclass_get_device(UCLASS_MOD_EXP, 0, &mod_exp_dev); 72 if (ret) { 73 printf("RSA: Can't find Modular Exp implementation\n"); 74 return -EINVAL; 75 } 76 77 ret = rsa_mod_exp(mod_exp_dev, sig, sig_len, prop, buf); 78 #else 79 ret = rsa_mod_exp_sw(sig, sig_len, prop, buf); 80 #endif 81 if (ret) { 82 debug("Error in Modular exponentation\n"); 83 return ret; 84 } 85 86 padding = algo->rsa_padding; 87 pad_len = algo->pad_len - algo->checksum_len; 88 89 /* Check pkcs1.5 padding bytes. */ 90 if (memcmp(buf, padding, pad_len)) { 91 debug("In RSAVerify(): Padding check failed!\n"); 92 return -EINVAL; 93 } 94 95 /* Check hash. */ 96 if (memcmp((uint8_t *)buf + pad_len, hash, sig_len - pad_len)) { 97 debug("In RSAVerify(): Hash check failed!\n"); 98 return -EACCES; 99 } 100 101 return 0; 102 } 103 104 /** 105 * rsa_verify_with_keynode() - Verify a signature against some data using 106 * information in node with prperties of RSA Key like modulus, exponent etc. 107 * 108 * Parse sign-node and fill a key_prop structure with properties of the 109 * key. Verify a RSA PKCS1.5 signature against an expected hash using 110 * the properties parsed 111 * 112 * @info: Specifies key and FIT information 113 * @hash: Pointer to the expected hash 114 * @sig: Signature 115 * @sig_len: Number of bytes in signature 116 * @node: Node having the RSA Key properties 117 * @return 0 if verified, -ve on error 118 */ 119 static int rsa_verify_with_keynode(struct image_sign_info *info, 120 const void *hash, uint8_t *sig, 121 uint sig_len, int node) 122 { 123 const void *blob = info->fdt_blob; 124 struct key_prop prop; 125 int length; 126 int ret = 0; 127 128 if (node < 0) { 129 debug("%s: Skipping invalid node", __func__); 130 return -EBADF; 131 } 132 133 prop.num_bits = fdtdec_get_int(blob, node, "rsa,num-bits", 0); 134 135 prop.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0); 136 137 prop.public_exponent = fdt_getprop(blob, node, "rsa,exponent", &length); 138 if (!prop.public_exponent || length < sizeof(uint64_t)) 139 prop.public_exponent = NULL; 140 141 prop.exp_len = sizeof(uint64_t); 142 143 prop.modulus = fdt_getprop(blob, node, "rsa,modulus", NULL); 144 145 prop.rr = fdt_getprop(blob, node, "rsa,r-squared", NULL); 146 147 if (!prop.num_bits || !prop.modulus) { 148 debug("%s: Missing RSA key info", __func__); 149 return -EFAULT; 150 } 151 152 ret = rsa_verify_key(&prop, sig, sig_len, hash, info->algo->checksum); 153 154 return ret; 155 } 156 157 int rsa_verify(struct image_sign_info *info, 158 const struct image_region region[], int region_count, 159 uint8_t *sig, uint sig_len) 160 { 161 const void *blob = info->fdt_blob; 162 /* Reserve memory for maximum checksum-length */ 163 uint8_t hash[info->algo->checksum->pad_len]; 164 int ndepth, noffset; 165 int sig_node, node; 166 char name[100]; 167 int ret; 168 169 /* 170 * Verify that the checksum-length does not exceed the 171 * rsa-signature-length 172 */ 173 if (info->algo->checksum->checksum_len > 174 info->algo->checksum->pad_len) { 175 debug("%s: invlaid checksum-algorithm %s for %s\n", 176 __func__, info->algo->checksum->name, info->algo->name); 177 return -EINVAL; 178 } 179 180 sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME); 181 if (sig_node < 0) { 182 debug("%s: No signature node found\n", __func__); 183 return -ENOENT; 184 } 185 186 /* Calculate checksum with checksum-algorithm */ 187 ret = info->algo->checksum->calculate(info->algo->checksum->name, 188 region, region_count, hash); 189 if (ret < 0) { 190 debug("%s: Error in checksum calculation\n", __func__); 191 return -EINVAL; 192 } 193 194 /* See if we must use a particular key */ 195 if (info->required_keynode != -1) { 196 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, 197 info->required_keynode); 198 if (!ret) 199 return ret; 200 } 201 202 /* Look for a key that matches our hint */ 203 snprintf(name, sizeof(name), "key-%s", info->keyname); 204 node = fdt_subnode_offset(blob, sig_node, name); 205 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node); 206 if (!ret) 207 return ret; 208 209 /* No luck, so try each of the keys in turn */ 210 for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth); 211 (noffset >= 0) && (ndepth > 0); 212 noffset = fdt_next_node(info->fit, noffset, &ndepth)) { 213 if (ndepth == 1 && noffset != node) { 214 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, 215 noffset); 216 if (!ret) 217 break; 218 } 219 } 220 221 return ret; 222 } 223