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dnsserver: Tighten DNS name checking

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Add checks for the maximum permitted length, maximum number of labels
and the maximum label length.  These extra checks will be used by the
DNS wild card handling.

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
BUG: https://bugzilla.samba.org/show_bug.cgi?id=12952
This commit is contained in:
Gary Lockyer 2017-08-03 15:12:51 +12:00 committed by Garming Sam
parent 1184770a76
commit 34acf5a992
2 changed files with 32 additions and 6 deletions
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3
librpc/idl/dns.idl
View File

@ -18,6 +18,9 @@ import "misc.idl", "dnsp.idl";
interface dns interface dns
{ {
const int DNS_SERVICE_PORT = 53; const int DNS_SERVICE_PORT = 53;
const int DNS_MAX_LABELS = 127;
const int DNS_MAX_DOMAIN_LENGTH = 253;
const int DNS_MAX_LABEL_LENGTH = 63;
typedef [public,bitmap16bit] bitmap { typedef [public,bitmap16bit] bitmap {
DNS_RCODE = 0x000F, DNS_RCODE = 0x000F,

33
source4/dns_server/dnsserver_common.c
View File

@ -246,26 +246,49 @@ static int rec_cmp(const struct dnsp_DnssrvRpcRecord *r1,
} }
/* /*
* Check for valid DNS names. These are names which are non-empty, do not * Check for valid DNS names. These are names which:
* start with a dot and do not have any empty segments. * - are non-empty
* - do not start with a dot
* - do not have any empty labels
* - have no more than 127 labels
* - are no longer than 253 characters
* - none of the labels exceed 63 characters
*/ */
WERROR dns_name_check(TALLOC_CTX *mem_ctx, size_t len, const char *name) WERROR dns_name_check(TALLOC_CTX *mem_ctx, size_t len, const char *name)
{ {
size_t i; size_t i;
unsigned int labels = 0;
unsigned int label_len = 0;
if (len == 0) { if (len == 0) {
return WERR_DS_INVALID_DN_SYNTAX; return WERR_DS_INVALID_DN_SYNTAX;
} }
if (len > 1 && name[0] == '.') {
return WERR_DS_INVALID_DN_SYNTAX;
}
if ((len - 1) > DNS_MAX_DOMAIN_LENGTH) {
return WERR_DS_INVALID_DN_SYNTAX;
}
for (i = 0; i < len - 1; i++) { for (i = 0; i < len - 1; i++) {
if (name[i] == '.' && name[i+1] == '.') { if (name[i] == '.' && name[i+1] == '.') {
return WERR_DS_INVALID_DN_SYNTAX; return WERR_DS_INVALID_DN_SYNTAX;
} }
} if (name[i] == '.') {
labels++;
if (len > 1 && name[0] == '.') { if (labels > DNS_MAX_LABELS) {
return WERR_DS_INVALID_DN_SYNTAX; return WERR_DS_INVALID_DN_SYNTAX;
} }
label_len = 0;
} else {
label_len++;
if (label_len > DNS_MAX_LABEL_LENGTH) {
return WERR_DS_INVALID_DN_SYNTAX;
}
}
}
return WERR_OK; return WERR_OK;
} }