security/integrity/ima/ima_template_lib.c

   1 /*
   2  * Copyright (C) 2013 Politecnico di Torino, Italy
   3  *                    TORSEC group -- http://security.polito.it
   4  *
   5  * Author: Roberto Sassu <roberto.sassu@polito.it>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation, version 2 of the
  10  * License.
  11  *
  12  * File: ima_template_lib.c
  13  *      Library of supported template fields.
  14  */
  15
  16 #include "ima_template_lib.h"
  17
  18 static bool ima_template_hash_algo_allowed(u8 algo)
  19 {
  20         if (algo == HASH_ALGO_SHA1 || algo == HASH_ALGO_MD5)
  21                 return true;
  22
  23         return false;
  24 }
  25
  26 enum data_formats {
  27         DATA_FMT_DIGEST = 0,
  28         DATA_FMT_DIGEST_WITH_ALGO,
  29         DATA_FMT_STRING,
  30         DATA_FMT_HEX
  31 };
  32
  33 static int ima_write_template_field_data(const void *data, const u32 datalen,
  34                                          enum data_formats datafmt,
  35                                          struct ima_field_data *field_data)
  36 {
  37         u8 *buf, *buf_ptr;
  38         u32 buflen = datalen;
  39
  40         if (datafmt == DATA_FMT_STRING)
  41                 buflen = datalen + 1;
  42
  43         buf = kzalloc(buflen, GFP_KERNEL);
  44         if (!buf)
  45                 return -ENOMEM;
  46
  47         memcpy(buf, data, datalen);
  48
  49         /*
  50          * Replace all space characters with underscore for event names and
  51          * strings. This avoid that, during the parsing of a measurements list,
  52          * filenames with spaces or that end with the suffix ' (deleted)' are
  53          * split into multiple template fields (the space is the delimitator
  54          * character for measurements lists in ASCII format).
  55          */
  56         if (datafmt == DATA_FMT_STRING) {
  57                 for (buf_ptr = buf; buf_ptr - buf < datalen; buf_ptr++)
  58                         if (*buf_ptr == ' ')
  59                                 *buf_ptr = '_';
  60         }
  61
  62         field_data->data = buf;
  63         field_data->len = buflen;
  64         return 0;
  65 }
  66
  67 static void ima_show_template_data_ascii(struct seq_file *m,
  68                                          enum ima_show_type show,
  69                                          enum data_formats datafmt,
  70                                          struct ima_field_data *field_data)
  71 {
  72         u8 *buf_ptr = field_data->data;
  73         u32 buflen = field_data->len;
  74
  75         switch (datafmt) {
  76         case DATA_FMT_DIGEST_WITH_ALGO:
  77                 buf_ptr = strnchr(field_data->data, buflen, ':');
  78                 if (buf_ptr != field_data->data)
  79                         seq_printf(m, "%s", field_data->data);
  80
  81                 /* skip ':' and '\0' */
  82                 buf_ptr += 2;
  83                 buflen -= buf_ptr - field_data->data;
  84         case DATA_FMT_DIGEST:
  85         case DATA_FMT_HEX:
  86                 if (!buflen)
  87                         break;
  88                 ima_print_digest(m, buf_ptr, buflen);
  89                 break;
  90         case DATA_FMT_STRING:
  91                 seq_printf(m, "%s", buf_ptr);
  92                 break;
  93         default:
  94                 break;
  95         }
  96 }
  97
  98 static void ima_show_template_data_binary(struct seq_file *m,
  99                                           enum ima_show_type show,
 100                                           enum data_formats datafmt,
 101                                           struct ima_field_data *field_data)
 102 {
 103         u32 len = (show == IMA_SHOW_BINARY_OLD_STRING_FMT) ?
 104             strlen(field_data->data) : field_data->len;
 105
 106         if (show != IMA_SHOW_BINARY_NO_FIELD_LEN) {
 107                 u32 field_len = !ima_canonical_fmt ? len : cpu_to_le32(len);
 108
 109                 ima_putc(m, &field_len, sizeof(field_len));
 110         }
 111
 112         if (!len)
 113                 return;
 114
 115         ima_putc(m, field_data->data, len);
 116 }
 117
 118 static void ima_show_template_field_data(struct seq_file *m,
 119                                          enum ima_show_type show,
 120                                          enum data_formats datafmt,
 121                                          struct ima_field_data *field_data)
 122 {
 123         switch (show) {
 124         case IMA_SHOW_ASCII:
 125                 ima_show_template_data_ascii(m, show, datafmt, field_data);
 126                 break;
 127         case IMA_SHOW_BINARY:
 128         case IMA_SHOW_BINARY_NO_FIELD_LEN:
 129         case IMA_SHOW_BINARY_OLD_STRING_FMT:
 130                 ima_show_template_data_binary(m, show, datafmt, field_data);
 131                 break;
 132         default:
 133                 break;
 134         }
 135 }
 136
 137 void ima_show_template_digest(struct seq_file *m, enum ima_show_type show,
 138                               struct ima_field_data *field_data)
 139 {
 140         ima_show_template_field_data(m, show, DATA_FMT_DIGEST, field_data);
 141 }
 142
 143 void ima_show_template_digest_ng(struct seq_file *m, enum ima_show_type show,
 144                                  struct ima_field_data *field_data)
 145 {
 146         ima_show_template_field_data(m, show, DATA_FMT_DIGEST_WITH_ALGO,
 147                                      field_data);
 148 }
 149
 150 void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
 151                               struct ima_field_data *field_data)
 152 {
 153         ima_show_template_field_data(m, show, DATA_FMT_STRING, field_data);
 154 }
 155
 156 void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
 157                            struct ima_field_data *field_data)
 158 {
 159         ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
 160 }
 161
 162 /**
 163  * ima_parse_buf() - Parses lengths and data from an input buffer
 164  * @bufstartp:       Buffer start address.
 165  * @bufendp:         Buffer end address.
 166  * @bufcurp:         Pointer to remaining (non-parsed) data.
 167  * @maxfields:       Length of fields array.
 168  * @fields:          Array containing lengths and pointers of parsed data.
 169  * @curfields:       Number of array items containing parsed data.
 170  * @len_mask:        Bitmap (if bit is set, data length should not be parsed).
 171  * @enforce_mask:    Check if curfields == maxfields and/or bufcurp == bufendp.
 172  * @bufname:         String identifier of the input buffer.
 173  *
 174  * Return: 0 on success, -EINVAL on error.
 175  */
 176 int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
 177                   int maxfields, struct ima_field_data *fields, int *curfields,
 178                   unsigned long *len_mask, int enforce_mask, char *bufname)
 179 {
 180         void *bufp = bufstartp;
 181         int i;
 182
 183         for (i = 0; i < maxfields; i++) {
 184                 if (len_mask == NULL || !test_bit(i, len_mask)) {
 185                         if (bufp > (bufendp - sizeof(u32)))
 186                                 break;
 187
 188                         fields[i].len = *(u32 *)bufp;
 189                         if (ima_canonical_fmt)
 190                                 fields[i].len = le32_to_cpu(fields[i].len);
 191
 192                         bufp += sizeof(u32);
 193                 }
 194
 195                 if (bufp > (bufendp - fields[i].len))
 196                         break;
 197
 198                 fields[i].data = bufp;
 199                 bufp += fields[i].len;
 200         }
 201
 202         if ((enforce_mask & ENFORCE_FIELDS) && i != maxfields) {
 203                 pr_err("%s: nr of fields mismatch: expected: %d, current: %d\n",
 204                        bufname, maxfields, i);
 205                 return -EINVAL;
 206         }
 207
 208         if ((enforce_mask & ENFORCE_BUFEND) && bufp != bufendp) {
 209                 pr_err("%s: buf end mismatch: expected: %p, current: %p\n",
 210                        bufname, bufendp, bufp);
 211                 return -EINVAL;
 212         }
 213
 214         if (curfields)
 215                 *curfields = i;
 216
 217         if (bufcurp)
 218                 *bufcurp = bufp;
 219
 220         return 0;
 221 }
 222
 223 static int ima_eventdigest_init_common(u8 *digest, u32 digestsize, u8 hash_algo,
 224                                        struct ima_field_data *field_data)
 225 {
 226         /*
 227          * digest formats:
 228          *  - DATA_FMT_DIGEST: digest
 229          *  - DATA_FMT_DIGEST_WITH_ALGO: [<hash algo>] + ':' + '\0' + digest,
 230          *    where <hash algo> is provided if the hash algoritm is not
 231          *    SHA1 or MD5
 232          */
 233         u8 buffer[CRYPTO_MAX_ALG_NAME + 2 + IMA_MAX_DIGEST_SIZE] = { 0 };
 234         enum data_formats fmt = DATA_FMT_DIGEST;
 235         u32 offset = 0;
 236
 237         if (hash_algo < HASH_ALGO__LAST) {
 238                 fmt = DATA_FMT_DIGEST_WITH_ALGO;
 239                 offset += snprintf(buffer, CRYPTO_MAX_ALG_NAME + 1, "%s",
 240                                    hash_algo_name[hash_algo]);
 241                 buffer[offset] = ':';
 242                 offset += 2;
 243         }
 244
 245         if (digest)
 246                 memcpy(buffer + offset, digest, digestsize);
 247         else
 248                 /*
 249                  * If digest is NULL, the event being recorded is a violation.
 250                  * Make room for the digest by increasing the offset of
 251                  * IMA_DIGEST_SIZE.
 252                  */
 253                 offset += IMA_DIGEST_SIZE;
 254
 255         return ima_write_template_field_data(buffer, offset + digestsize,
 256                                              fmt, field_data);
 257 }
 258
 259 /*
 260  * This function writes the digest of an event (with size limit).
 261  */
 262 int ima_eventdigest_init(struct ima_event_data *event_data,
 263                          struct ima_field_data *field_data)
 264 {
 265         struct {
 266                 struct ima_digest_data hdr;
 267                 char digest[IMA_MAX_DIGEST_SIZE];
 268         } hash;
 269         u8 *cur_digest = NULL;
 270         u32 cur_digestsize = 0;
 271         struct inode *inode;
 272         int result;
 273
 274         memset(&hash, 0, sizeof(hash));
 275
 276         if (event_data->violation)      /* recording a violation. */
 277                 goto out;
 278
 279         if (ima_template_hash_algo_allowed(event_data->iint->ima_hash->algo)) {
 280                 cur_digest = event_data->iint->ima_hash->digest;
 281                 cur_digestsize = event_data->iint->ima_hash->length;
 282                 goto out;
 283         }
 284
 285         if (!event_data->file)  /* missing info to re-calculate the digest */
 286                 return -EINVAL;
 287
 288         inode = file_inode(event_data->file);
 289         hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
 290             ima_hash_algo : HASH_ALGO_SHA1;
 291         result = ima_calc_file_hash(event_data->file, &hash.hdr);
 292         if (result) {
 293                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
 294                                     event_data->filename, "collect_data",
 295                                     "failed", result, 0);
 296                 return result;
 297         }
 298         cur_digest = hash.hdr.digest;
 299         cur_digestsize = hash.hdr.length;
 300 out:
 301         return ima_eventdigest_init_common(cur_digest, cur_digestsize,
 302                                            HASH_ALGO__LAST, field_data);
 303 }
 304
 305 /*
 306  * This function writes the digest of an event (without size limit).
 307  */
 308 int ima_eventdigest_ng_init(struct ima_event_data *event_data,
 309                             struct ima_field_data *field_data)
 310 {
 311         u8 *cur_digest = NULL, hash_algo = HASH_ALGO_SHA1;
 312         u32 cur_digestsize = 0;
 313
 314         if (event_data->violation)      /* recording a violation. */
 315                 goto out;
 316
 317         cur_digest = event_data->iint->ima_hash->digest;
 318         cur_digestsize = event_data->iint->ima_hash->length;
 319
 320         hash_algo = event_data->iint->ima_hash->algo;
 321 out:
 322         return ima_eventdigest_init_common(cur_digest, cur_digestsize,
 323                                            hash_algo, field_data);
 324 }
 325
 326 static int ima_eventname_init_common(struct ima_event_data *event_data,
 327                                      struct ima_field_data *field_data,
 328                                      bool size_limit)
 329 {
 330         const char *cur_filename = NULL;
 331         u32 cur_filename_len = 0;
 332
 333         BUG_ON(event_data->filename == NULL && event_data->file == NULL);
 334
 335         if (event_data->filename) {
 336                 cur_filename = event_data->filename;
 337                 cur_filename_len = strlen(event_data->filename);
 338
 339                 if (!size_limit || cur_filename_len <= IMA_EVENT_NAME_LEN_MAX)
 340                         goto out;
 341         }
 342
 343         if (event_data->file) {
 344                 cur_filename = event_data->file->f_path.dentry->d_name.name;
 345                 cur_filename_len = strlen(cur_filename);
 346         } else
 347                 /*
 348                  * Truncate filename if the latter is too long and
 349                  * the file descriptor is not available.
 350                  */
 351                 cur_filename_len = IMA_EVENT_NAME_LEN_MAX;
 352 out:
 353         return ima_write_template_field_data(cur_filename, cur_filename_len,
 354                                              DATA_FMT_STRING, field_data);
 355 }
 356
 357 /*
 358  * This function writes the name of an event (with size limit).
 359  */
 360 int ima_eventname_init(struct ima_event_data *event_data,
 361                        struct ima_field_data *field_data)
 362 {
 363         return ima_eventname_init_common(event_data, field_data, true);
 364 }
 365
 366 /*
 367  * This function writes the name of an event (without size limit).
 368  */
 369 int ima_eventname_ng_init(struct ima_event_data *event_data,
 370                           struct ima_field_data *field_data)
 371 {
 372         return ima_eventname_init_common(event_data, field_data, false);
 373 }
 374
 375 /*
 376  *  ima_eventsig_init - include the file signature as part of the template data
 377  */
 378 int ima_eventsig_init(struct ima_event_data *event_data,
 379                       struct ima_field_data *field_data)
 380 {
 381         enum data_formats fmt = DATA_FMT_HEX;
 382         struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
 383         int xattr_len = event_data->xattr_len;
 384         int rc = 0;
 385
 386         if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
 387                 goto out;
 388
 389         rc = ima_write_template_field_data(xattr_value, xattr_len, fmt,
 390                                            field_data);
 391 out:
 392         return rc;
 393 }