src/libudev/libudev-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <ctype.h>
   4 #include <errno.h>
   5
   6 #include "sd-device.h"
   7
   8 #include "device-nodes.h"
   9 #include "libudev-util.h"
  10 #include "string-util.h"
  11 #include "strxcpyx.h"
  12 #include "utf8.h"
  13
  14 /**
  15  * SECTION:libudev-util
  16  * @short_description: utils
  17  *
  18  * Utilities useful when dealing with devices and device node names.
  19  */
  20
  21 /* handle "[<SUBSYSTEM>/<KERNEL>]<attribute>" format */
  22 int util_resolve_subsys_kernel(const char *string, char *result, size_t maxsize, bool read_value) {
  23         char temp[UTIL_PATH_SIZE], *subsys, *sysname, *attr;
  24         _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
  25         const char *val;
  26         int r;
  27
  28         if (string[0] != '[')
  29                 return -EINVAL;
  30
  31         strscpy(temp, sizeof(temp), string);
  32
  33         subsys = &temp[1];
  34
  35         sysname = strchr(subsys, '/');
  36         if (!sysname)
  37                 return -EINVAL;
  38         sysname[0] = '\0';
  39         sysname = &sysname[1];
  40
  41         attr = strchr(sysname, ']');
  42         if (!attr)
  43                 return -EINVAL;
  44         attr[0] = '\0';
  45         attr = &attr[1];
  46         if (attr[0] == '/')
  47                 attr = &attr[1];
  48         if (attr[0] == '\0')
  49                 attr = NULL;
  50
  51         if (read_value && !attr)
  52                 return -EINVAL;
  53
  54         r = sd_device_new_from_subsystem_sysname(&dev, subsys, sysname);
  55         if (r < 0)
  56                 return r;
  57
  58         if (read_value) {
  59                 r = sd_device_get_sysattr_value(dev, attr, &val);
  60                 if (r < 0 && r != -ENOENT)
  61                         return r;
  62                 if (r == -ENOENT)
  63                         result[0] = '\0';
  64                 else
  65                         strscpy(result, maxsize, val);
  66                 log_debug("value '[%s/%s]%s' is '%s'", subsys, sysname, attr, result);
  67         } else {
  68                 r = sd_device_get_syspath(dev, &val);
  69                 if (r < 0)
  70                         return r;
  71
  72                 strscpyl(result, maxsize, val, attr ? "/" : NULL, attr ?: NULL, NULL);
  73                 log_debug("path '[%s/%s]%s' is '%s'", subsys, sysname, strempty(attr), result);
  74         }
  75         return 0;
  76 }
  77
  78 size_t util_path_encode(const char *src, char *dest, size_t size) {
  79         size_t i, j;
  80
  81         assert(src);
  82         assert(dest);
  83
  84         for (i = 0, j = 0; src[i] != '\0'; i++) {
  85                 if (src[i] == '/') {
  86                         if (j+4 >= size) {
  87                                 j = 0;
  88                                 break;
  89                         }
  90                         memcpy(&dest[j], "\\x2f", 4);
  91                         j += 4;
  92                 } else if (src[i] == '\\') {
  93                         if (j+4 >= size) {
  94                                 j = 0;
  95                                 break;
  96                         }
  97                         memcpy(&dest[j], "\\x5c", 4);
  98                         j += 4;
  99                 } else {
 100                         if (j+1 >= size) {
 101                                 j = 0;
 102                                 break;
 103                         }
 104                         dest[j] = src[i];
 105                         j++;
 106                 }
 107         }
 108         dest[j] = '\0';
 109         return j;
 110 }
 111
 112 /*
 113  * Copy from 'str' to 'to', while removing all leading and trailing whitespace,
 114  * and replacing each run of consecutive whitespace with a single underscore.
 115  * The chars from 'str' are copied up to the \0 at the end of the string, or
 116  * at most 'len' chars.  This appends \0 to 'to', at the end of the copied
 117  * characters.
 118  *
 119  * If 'len' chars are copied into 'to', the final \0 is placed at len+1
 120  * (i.e. 'to[len] = \0'), so the 'to' buffer must have at least len+1
 121  * chars available.
 122  *
 123  * Note this may be called with 'str' == 'to', i.e. to replace whitespace
 124  * in-place in a buffer.  This function can handle that situation.
 125  */
 126 size_t util_replace_whitespace(const char *str, char *to, size_t len) {
 127         bool is_space = false;
 128         const char *p = str;
 129         size_t j;
 130
 131         assert(str);
 132         assert(to);
 133
 134         p += strspn(p, WHITESPACE);
 135
 136         for (j = 0; j < len && *p != '\0'; p++) {
 137                 if (isspace(*p)) {
 138                         is_space = true;
 139                         continue;
 140                 }
 141
 142                 if (is_space) {
 143                         if (j + 1 >= len)
 144                                 break;
 145
 146                         to[j++] = '_';
 147                         is_space = false;
 148                 }
 149                 to[j++] = *p;
 150         }
 151
 152         to[j] = '\0';
 153         return j;
 154 }
 155
 156 /* allow chars in whitelist, plain ascii, hex-escaping and valid utf8 */
 157 size_t util_replace_chars(char *str, const char *white) {
 158         size_t i = 0, replaced = 0;
 159
 160         assert(str);
 161
 162         while (str[i] != '\0') {
 163                 int len;
 164
 165                 if (whitelisted_char_for_devnode(str[i], white)) {
 166                         i++;
 167                         continue;
 168                 }
 169
 170                 /* accept hex encoding */
 171                 if (str[i] == '\\' && str[i+1] == 'x') {
 172                         i += 2;
 173                         continue;
 174                 }
 175
 176                 /* accept valid utf8 */
 177                 len = utf8_encoded_valid_unichar(&str[i]);
 178                 if (len > 1) {
 179                         i += len;
 180                         continue;
 181                 }
 182
 183                 /* if space is allowed, replace whitespace with ordinary space */
 184                 if (isspace(str[i]) && white && strchr(white, ' ')) {
 185                         str[i] = ' ';
 186                         i++;
 187                         replaced++;
 188                         continue;
 189                 }
 190
 191                 /* everything else is replaced with '_' */
 192                 str[i] = '_';
 193                 i++;
 194                 replaced++;
 195         }
 196         return replaced;
 197 }
 198
 199 /**
 200  * udev_util_encode_string:
 201  * @str: input string to be encoded
 202  * @str_enc: output string to store the encoded input string
 203  * @len: maximum size of the output string, which may be
 204  *       four times as long as the input string
 205  *
 206  * Encode all potentially unsafe characters of a string to the
 207  * corresponding 2 char hex value prefixed by '\x'.
 208  *
 209  * Returns: 0 if the entire string was copied, non-zero otherwise.
 210  **/
 211 _public_ int udev_util_encode_string(const char *str, char *str_enc, size_t len) {
 212         return encode_devnode_name(str, str_enc, len);
 213 }