wimlib.net Git - wimlib/blob - src/symlink.c

   1 #include "dentry.h"
   2 #include "io.h"
   3 #include "lookup_table.h"
   4 #include "sha1.h"
   5 #include <errno.h>
   6
   7 /*
   8  * Find the symlink target of a symbolic link or junction point in the WIM.
   9  *
  10  * See http://msdn.microsoft.com/en-us/library/cc232006(v=prot.10).aspx
  11  * Except the first 8 bytes aren't included in the resource (presumably because
  12  * we already know the reparse tag from the dentry, and we already know the
  13  * reparse tag len from the lookup table entry resource length).
  14  */
  15 static ssize_t get_symlink_name(const u8 *resource, size_t resource_len,
  16                                 char *buf, size_t buf_len,
  17                                 u32 reparse_tag)
  18 {
  19         const u8 *p = resource;
  20         u16 substitute_name_offset;
  21         u16 substitute_name_len;
  22         u16 print_name_offset;
  23         u16 print_name_len;
  24         char *link_target;
  25         size_t link_target_len;
  26         ssize_t ret;
  27         unsigned header_size;
  28         char *translated_target;
  29         bool is_absolute;
  30         u32 flags;
  31
  32         if (resource_len < 12)
  33                 return -EIO;
  34         p = get_u16(p, &substitute_name_offset);
  35         p = get_u16(p, &substitute_name_len);
  36         p = get_u16(p, &print_name_offset);
  37         p = get_u16(p, &print_name_len);
  38         get_u32(p, &flags);
  39
  40         wimlib_assert(reparse_tag == WIM_IO_REPARSE_TAG_SYMLINK ||
  41                       reparse_tag == WIM_IO_REPARSE_TAG_MOUNT_POINT);
  42
  43         /* I think that some junction points incorrectly get marked as symbolic
  44          * links.  So, parse the link buffer as a symlink if the flags seem
  45          * plausible. */
  46         if (flags <= 1)
  47                 reparse_tag = WIM_IO_REPARSE_TAG_SYMLINK;
  48
  49         if (reparse_tag == WIM_IO_REPARSE_TAG_MOUNT_POINT) {
  50                 header_size = 8;
  51         } else {
  52                 is_absolute = (flags & 1) ? false : true;
  53                 header_size = 12;
  54                 p += 4;
  55         }
  56         if (header_size + substitute_name_offset + substitute_name_len > resource_len)
  57                 return -EIO;
  58         link_target = utf16_to_utf8(p + substitute_name_offset,
  59                                     substitute_name_len,
  60                                     &link_target_len);
  61
  62         if (!link_target)
  63                 return -EIO;
  64
  65         if (link_target_len + 1 > buf_len) {
  66                 ret = -ENAMETOOLONG;
  67                 goto out;
  68         }
  69
  70         translated_target = link_target;
  71         if (reparse_tag == WIM_IO_REPARSE_TAG_MOUNT_POINT || is_absolute) {
  72                 if (link_target_len < 7
  73                       || memcmp(translated_target, "\\??\\", 4) != 0
  74                       || translated_target[4] == '\0'
  75                       || translated_target[5] != ':'
  76                       || translated_target[6] != '\\') {
  77                         ret = -EIO;
  78                         goto out;
  79                 }
  80                 translated_target += 4;
  81                 link_target_len -= 4;
  82                 /* There's a drive letter, so just leave the backslashes since
  83                  * it won't go anyhwere on UNIX anyway... */
  84         } else {
  85                 for (size_t i = 0; i < link_target_len; i++)
  86                         if (translated_target[i] == '\\')
  87                                 translated_target[i] = '/';
  88         }
  89
  90         memcpy(buf, translated_target, link_target_len + 1);
  91         ret = link_target_len;
  92 out:
  93         FREE(link_target);
  94         return ret;
  95 }
  96
  97 void *make_symlink_reparse_data_buf(const char *symlink_target, size_t *len_ret)
  98 {
  99         size_t utf8_len = strlen(symlink_target);
 100         size_t utf16_len;
 101         char *name_utf16 = utf8_to_utf16(symlink_target, utf8_len, &utf16_len);
 102         if (!name_utf16)
 103                 return NULL;
 104         /*DEBUG("utf16_len = %zu", utf16_len);*/
 105         for (size_t i = 0; i < utf16_len / 2; i++)
 106                 if (((u16*)name_utf16)[i] == to_le16('/'))
 107                         ((u16*)name_utf16)[i] = to_le16('\\');
 108         size_t len = 12 + utf16_len * 2;
 109         void *buf = MALLOC(len);
 110         if (!buf)
 111                 goto out;
 112         /* XXX Fix absolute paths */
 113
 114         u8 *p = buf;
 115         p = put_u16(p, 0); /* Substitute name offset */
 116         p = put_u16(p, utf16_len); /* Substitute name length */
 117         p = put_u16(p, utf16_len); /* Print name offset */
 118         p = put_u16(p, utf16_len); /* Print name length */
 119         p = put_u32(p, 1);
 120         p = put_bytes(p, utf16_len, name_utf16);
 121         p = put_bytes(p, utf16_len, name_utf16);
 122         /*DEBUG("utf16_len = %zu, len = %zu", utf16_len, len);*/
 123         *len_ret = len;
 124 out:
 125         FREE(name_utf16);
 126         return buf;
 127 }
 128
 129 /* Get the symlink target from a dentry that's already checked to be either a
 130  * "real" symlink or a junction point. */
 131 ssize_t dentry_readlink(const struct dentry *dentry, char *buf, size_t buf_len,
 132                         const WIMStruct *w)
 133 {
 134         struct resource_entry *res_entry;
 135         struct lookup_table_entry *lte;
 136         u16 i = 0;
 137         const u8 *hash = dentry->hash;
 138
 139         wimlib_assert(dentry_is_symlink(dentry));
 140
 141         while (1) {
 142                 if ((lte = __lookup_resource(w->lookup_table, hash)))
 143                         break;
 144                 if (i == dentry->num_ads)
 145                         return -EIO;
 146                 hash = dentry->ads_entries[i].hash;
 147                 i++;
 148         }
 149         res_entry = &lte->resource_entry;
 150         if (res_entry->original_size > 10000)
 151                 return -EIO;
 152
 153         char __res_buf[res_entry->original_size];
 154         const char *res_buf;
 155         if (lte->is_symlink && lte->symlink_buf) {
 156                 res_buf = lte->symlink_buf;
 157         } else {
 158                 res_buf = __res_buf;
 159                 if (read_full_resource(w->fp, res_entry->size,
 160                                        res_entry->original_size,
 161                                        res_entry->offset,
 162                                        wim_resource_compression_type(w, res_entry),
 163                                        __res_buf) != 0)
 164                         return -EIO;
 165                 res_buf = __res_buf;
 166         }
 167         return get_symlink_name(res_buf, res_entry->original_size, buf,
 168                                 buf_len, dentry->reparse_tag);
 169 }
 170
 171 static int dentry_set_symlink_buf(struct dentry *dentry,
 172                                   const u8 symlink_buf_hash[])
 173 {
 174         struct ads_entry *ads_entries;
 175
 176         ads_entries = CALLOC(2, sizeof(struct ads_entry));
 177         if (!ads_entries)
 178                 return WIMLIB_ERR_NOMEM;
 179         memcpy(ads_entries[1].hash, symlink_buf_hash, WIM_HASH_SIZE);
 180         dentry_free_ads_entries(dentry);
 181         dentry->num_ads = 2;
 182         dentry->ads_entries = ads_entries;
 183         return 0;
 184 }
 185
 186 int dentry_set_symlink(struct dentry *dentry, const char *target,
 187                        struct lookup_table *lookup_table)
 188
 189 {
 190         int ret;
 191         size_t symlink_buf_len;
 192         struct lookup_table_entry *lte = NULL, *existing_lte;
 193         u8 symlink_buf_hash[WIM_HASH_SIZE];
 194         void *symlink_buf;
 195
 196         symlink_buf = make_symlink_reparse_data_buf(target, &symlink_buf_len);
 197         if (!symlink_buf)
 198                 return WIMLIB_ERR_NOMEM;
 199
 200         DEBUG("Made symlink reparse data buf (len = %zu, name len = %zu)",
 201                         symlink_buf_len, ret);
 202
 203         sha1_buffer(symlink_buf, symlink_buf_len, symlink_buf_hash);
 204
 205         existing_lte = __lookup_resource(lookup_table, symlink_buf_hash);
 206
 207         if (existing_lte) {
 208                 existing_lte->refcnt++;
 209         } else {
 210                 DEBUG("Creating new lookup table entry for symlink buf");
 211                 lte = new_lookup_table_entry();
 212                 if (!lte) {
 213                         ret = WIMLIB_ERR_NOMEM;
 214                         goto out_free_symlink_buf;
 215                 }
 216                 lte->is_symlink = true;
 217                 lte->symlink_buf = symlink_buf;
 218                 lte->resource_entry.original_size = symlink_buf_len;
 219                 lte->resource_entry.size = symlink_buf_len;
 220                 memcpy(lte->hash, symlink_buf_hash, WIM_HASH_SIZE);
 221         }
 222
 223         ret = dentry_set_symlink_buf(dentry, symlink_buf_hash);
 224
 225         if (ret != 0)
 226                 goto out_free_lte;
 227
 228         DEBUG("Loaded symlink buf");
 229
 230         if (!existing_lte)
 231                 lookup_table_insert(lookup_table, lte);
 232         return 0;
 233 out_free_lte:
 234         FREE(lte);
 235 out_free_symlink_buf:
 236         FREE(symlink_buf);
 237         return ret;
 238 }