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