crypto/der.c

   1 /*
   2  * QEMU Crypto ASN.1 DER decoder
   3  *
   4  * Copyright (c) 2022 Bytedance
   5  * Author: lei he <helei.sig11@bytedance.com>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  19  *
  20  */
  21
  22 #include "qemu/osdep.h"
  23 #include "crypto/der.h"
  24
  25 enum QCryptoDERTypeTag {
  26     QCRYPTO_DER_TYPE_TAG_BOOL = 0x1,
  27     QCRYPTO_DER_TYPE_TAG_INT = 0x2,
  28     QCRYPTO_DER_TYPE_TAG_BIT_STR = 0x3,
  29     QCRYPTO_DER_TYPE_TAG_OCT_STR = 0x4,
  30     QCRYPTO_DER_TYPE_TAG_OCT_NULL = 0x5,
  31     QCRYPTO_DER_TYPE_TAG_OCT_OID = 0x6,
  32     QCRYPTO_DER_TYPE_TAG_SEQ = 0x10,
  33     QCRYPTO_DER_TYPE_TAG_SET = 0x11,
  34 };
  35
  36 #define QCRYPTO_DER_CONSTRUCTED_MASK 0x20
  37 #define QCRYPTO_DER_SHORT_LEN_MASK 0x80
  38
  39 static uint8_t qcrypto_der_peek_byte(const uint8_t **data, size_t *dlen)
  40 {
  41     return **data;
  42 }
  43
  44 static void qcrypto_der_cut_nbytes(const uint8_t **data,
  45                                    size_t *dlen,
  46                                    size_t nbytes)
  47 {
  48     *data += nbytes;
  49     *dlen -= nbytes;
  50 }
  51
  52 static uint8_t qcrypto_der_cut_byte(const uint8_t **data, size_t *dlen)
  53 {
  54     uint8_t val = qcrypto_der_peek_byte(data, dlen);
  55
  56     qcrypto_der_cut_nbytes(data, dlen, 1);
  57
  58     return val;
  59 }
  60
  61 static int qcrypto_der_invoke_callback(QCryptoDERDecodeCb cb, void *ctx,
  62                                        const uint8_t *value, size_t vlen,
  63                                        Error **errp)
  64 {
  65     if (!cb) {
  66         return 0;
  67     }
  68
  69     return cb(ctx, value, vlen, errp);
  70 }
  71
  72 static int qcrypto_der_extract_definite_data(const uint8_t **data, size_t *dlen,
  73                                              QCryptoDERDecodeCb cb, void *ctx,
  74                                              Error **errp)
  75 {
  76     const uint8_t *value;
  77     size_t vlen = 0;
  78     uint8_t byte_count = qcrypto_der_cut_byte(data, dlen);
  79
  80     /* short format of definite-length */
  81     if (!(byte_count & QCRYPTO_DER_SHORT_LEN_MASK)) {
  82         if (byte_count > *dlen) {
  83             error_setg(errp, "Invalid content length: %u", byte_count);
  84             return -1;
  85         }
  86
  87         value = *data;
  88         vlen = byte_count;
  89         qcrypto_der_cut_nbytes(data, dlen, vlen);
  90
  91         if (qcrypto_der_invoke_callback(cb, ctx, value, vlen, errp) != 0) {
  92             return -1;
  93         }
  94         return vlen;
  95     }
  96
  97     /* Ignore highest bit */
  98     byte_count &= ~QCRYPTO_DER_SHORT_LEN_MASK;
  99
 100     /*
 101      * size_t is enough to store the value of length, although the DER
 102      * encoding standard supports larger length.
 103      */
 104     if (byte_count > sizeof(size_t)) {
 105         error_setg(errp, "Invalid byte count of content length: %u",
 106                    byte_count);
 107         return -1;
 108     }
 109
 110     if (byte_count > *dlen) {
 111         error_setg(errp, "Invalid content length: %u", byte_count);
 112         return -1;
 113     }
 114     while (byte_count--) {
 115         vlen <<= 8;
 116         vlen += qcrypto_der_cut_byte(data, dlen);
 117     }
 118
 119     if (vlen > *dlen) {
 120         error_setg(errp, "Invalid content length: %zu", vlen);
 121         return -1;
 122     }
 123
 124     value = *data;
 125     qcrypto_der_cut_nbytes(data, dlen, vlen);
 126
 127     if (qcrypto_der_invoke_callback(cb, ctx, value, vlen, errp) != 0) {
 128         return -1;
 129     }
 130     return vlen;
 131 }
 132
 133 static int qcrypto_der_extract_data(const uint8_t **data, size_t *dlen,
 134                                     QCryptoDERDecodeCb cb, void *ctx,
 135                                     Error **errp)
 136 {
 137     uint8_t val;
 138     if (*dlen < 1) {
 139         error_setg(errp, "Need more data");
 140         return -1;
 141     }
 142     val = qcrypto_der_peek_byte(data, dlen);
 143
 144     /* must use definite length format */
 145     if (val == QCRYPTO_DER_SHORT_LEN_MASK) {
 146         error_setg(errp, "Only definite length format is allowed");
 147         return -1;
 148     }
 149
 150     return qcrypto_der_extract_definite_data(data, dlen, cb, ctx, errp);
 151 }
 152
 153 int qcrypto_der_decode_int(const uint8_t **data, size_t *dlen,
 154                            QCryptoDERDecodeCb cb, void *ctx, Error **errp)
 155 {
 156     uint8_t tag;
 157     if (*dlen < 1) {
 158         error_setg(errp, "Need more data");
 159         return -1;
 160     }
 161     tag = qcrypto_der_cut_byte(data, dlen);
 162
 163     /* INTEGER must encoded in primitive-form */
 164     if (tag != QCRYPTO_DER_TYPE_TAG_INT) {
 165         error_setg(errp, "Invalid integer type tag: %u", tag);
 166         return -1;
 167     }
 168
 169     return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
 170 }
 171
 172 int qcrypto_der_decode_seq(const uint8_t **data, size_t *dlen,
 173                            QCryptoDERDecodeCb cb, void *ctx, Error **errp)
 174 {
 175     uint8_t tag;
 176     if (*dlen < 1) {
 177         error_setg(errp, "Need more data");
 178         return -1;
 179     }
 180     tag = qcrypto_der_cut_byte(data, dlen);
 181
 182     /* SEQUENCE must use constructed form */
 183     if (tag != (QCRYPTO_DER_TYPE_TAG_SEQ | QCRYPTO_DER_CONSTRUCTED_MASK)) {
 184         error_setg(errp, "Invalid type sequence tag: %u", tag);
 185         return -1;
 186     }
 187
 188     return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
 189 }