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vvfat: Check that updated filenames are valid

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FAT allows only a restricted set of characters in file names, and for
some of the illegal characters, it's actually important that we catch
them: If filenames can contain '/', the guest can construct filenames
containing "../" and escape from the assigned vvfat directory. The same
problem could arise if ".." was ever accepted as a literal filename.

Fix this by adding a check that all filenames are valid in
check_directory_consistency().

Reported-by: Nathan Huckleberry <nhuck15@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200623175534.38286-2-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2020-06-23 19:55:33 +02:00
parent f10802d2c9
commit c79e243ed6
1 changed files with 24 additions and 1 deletions
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25
block/vvfat.c
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@ -520,12 +520,31 @@ static void set_begin_of_direntry(direntry_t* direntry, uint32_t begin)
direntry->begin_hi = cpu_to_le16((begin >> 16) & 0xffff);
}
static bool valid_filename(const unsigned char *name)
{
unsigned char c;
if (!strcmp((const char*)name, ".") || !strcmp((const char*)name, "..")) {
return false;
}
for (; (c = *name); name++) {
if (!((c >= '0' && c <= '9') ||
(c >= 'A' && c <= 'Z') ||
(c >= 'a' && c <= 'z') ||
c > 127 ||
strchr("$%'-_@~`!(){}^#&.+,;=[]", c) != NULL))
{
return false;
}
}
return true;
}
static uint8_t to_valid_short_char(gunichar c)
{
c = g_unichar_toupper(c);
if ((c >= '0' && c <= '9') ||
(c >= 'A' && c <= 'Z') ||
strchr("$%'-_@~`!(){}^#&", c) != 0) {
strchr("$%'-_@~`!(){}^#&", c) != NULL) {
return c;
} else {
return 0;
@ -2098,6 +2117,10 @@ DLOG(fprintf(stderr, "check direntry %d:\n", i); print_direntry(direntries + i))
}
lfn.checksum = 0x100; /* cannot use long name twice */
if (!valid_filename(lfn.name)) {
fprintf(stderr, "Invalid file name\n");
goto fail;
}
if (path_len + 1 + lfn.len >= PATH_MAX) {
fprintf(stderr, "Name too long: %s/%s\n", path, lfn.name);
goto fail;