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Fix OOB read in TCP/IP interface hostname validation #586

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Fix OOB read in TCP/IP interface hostname validation #586

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82 changes: 46 additions & 36 deletions source/src/cip/ciptcpipinterface.c
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Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,7 @@ static bool isalnum_c(const EipByte byte) {
/** Check passed string to conform to the rules for host name labels
*
* @param label pointer to the label string to check
* @param label_length length of the label string to check
* @return true if label is valid
*
* A host name label is a string of length 1 to 63 characters with
Expand All @@ -119,20 +120,24 @@ static bool isalnum_c(const EipByte byte) {
* The minimum length of 1 is checked but not the maximum length
* that has already been enforced on data reception.
*/
static bool IsValidNameLabel(const EipByte *label) {
if (!isalnum_c(*label) ) {
static bool IsValidNameLabel(const EipByte *label, const size_t label_length) {
if(0 == label_length || !isalnum_c(label[0]) ) {
return false;
}
++label;
while ('\0' != *label && (isalnum_c(*label) || '-' == *label) ) {
++label;

for(size_t i = 1; i < label_length; i++) {
if(!(isalnum_c(label[i]) || '-' == label[i]) ) {
return false;
}
}
return ('\0' == *label && '-' != label[-1]);

return '-' != label[label_length - 1];
}

/** Check if domain is a valid domain
*
* @param p_domain pointer to domain string to check
* @param domain_length length of domain string to check
* @return true if domain is valid
*
* We check here for domain names that are part of a valid host name.
Expand All @@ -143,33 +148,32 @@ static bool IsValidNameLabel(const EipByte *label) {
* be converted to punycode (see https://www.punycoder.com/) by
* the user in advance.
*/
static bool IsValidDomain(EipByte *domain) {
bool status = true;
static bool IsValidDomain(const EipByte *domain, const size_t domain_length) {
size_t label_start = 0;

OPENER_TRACE_INFO("Enter '%s'->", domain);
if ('.' == *domain) { /* Forbid leading dot */
OPENER_TRACE_INFO("Enter '%.*s'->\n", (int) domain_length, domain);
if(0 == domain_length || '.' == domain[0] || '.' == domain[domain_length - 1]) {
return false;
}
EipByte *dot = (EipByte *)strchr( (char *)domain, '.' );
if (dot) {
bool rc;

*dot = '\0';
status &= rc = IsValidNameLabel(domain);
OPENER_TRACE_INFO("Checked %d '%s'\n", rc, domain);
if ('\0' != dot[1]) {
status &= IsValidDomain(dot + 1);
}
else { /* Forbid trailing dot */
status = false;

for(size_t i = 0; i <= domain_length; i++) {
if(i == domain_length || '.' == domain[i]) {
const size_t label_length = i - label_start;
const bool status = IsValidNameLabel(domain + label_start, label_length);
OPENER_TRACE_INFO("Checked %d '%.*s'\n",
status,
(int) label_length,
domain + label_start);
if(!status) {
return false;
}
if(i < domain_length) {
label_start = i + 1;
}
}
*dot = '.';
}
else {
status = IsValidNameLabel(domain);
OPENER_TRACE_INFO("Check end %d '%s'\n", status, domain);
}
return status;

return true;
}


Expand Down Expand Up @@ -442,21 +446,24 @@ int DecodeCipTcpIpInterfaceConfiguration( /* Attribute 5 */
}
SetCipStringByData(&if_cfg.domain_name, domain_name_length,
message_router_request->data);
domain_name_length = (domain_name_length + 1) & (~0x0001u); /* Align for possible pad byte */
OPENER_TRACE_INFO("Domain: ds %hu '%s'\n",
OPENER_TRACE_INFO("Domain: ds %hu '%.*s'\n",
domain_name_length,
(int) if_cfg.domain_name.length,
if_cfg.domain_name.string);
const CipUint padded_domain_name_length =
(domain_name_length + 1) & (~0x0001u); /* Align for possible pad byte */

if (!IsValidNetworkConfig(&if_cfg)
|| (domain_name_length > 0
&& !IsValidDomain(if_cfg.domain_name.string))) {
&& !IsValidDomain(if_cfg.domain_name.string,
if_cfg.domain_name.length))) {
message_router_response->general_status =
kCipErrorInvalidAttributeValue;
return number_of_decoded_bytes;
}

*data = if_cfg; //write data to attribute
number_of_decoded_bytes = 20 + domain_name_length;
number_of_decoded_bytes = 20 + padded_domain_name_length;

/* Tell that this configuration change becomes active after a reset */
g_tcpip.status |= kTcpipStatusIfaceCfgPend;
Expand Down Expand Up @@ -486,12 +493,15 @@ int DecodeCipTcpIpInterfaceHostName( /* Attribute 6 */
SetCipStringByData(&tmp_host_name,
host_name_length,
message_router_request->data);
host_name_length = (host_name_length + 1) & (~0x0001u); /* Align for possible pad byte */
OPENER_TRACE_INFO("Host Name: ds %hu '%s'\n",
OPENER_TRACE_INFO("Host Name: ds %hu '%.*s'\n",
host_name_length,
(int) tmp_host_name.length,
tmp_host_name.string);
const CipUint padded_host_name_length =
(host_name_length + 1) & (~0x0001u); /* Align for possible pad byte */

if (!IsValidNameLabel(tmp_host_name.string) ) {
if (!IsValidNameLabel(tmp_host_name.string,
tmp_host_name.length) ) {
message_router_response->general_status =
kCipErrorInvalidAttributeValue;
return number_of_decoded_bytes;
Expand All @@ -502,6 +512,7 @@ int DecodeCipTcpIpInterfaceHostName( /* Attribute 6 */
/* Tell that this configuration change becomes active after a reset */
g_tcpip.status |= kTcpipStatusIfaceCfgPend;
message_router_response->general_status = kCipErrorSuccess;
number_of_decoded_bytes = 2 + padded_host_name_length;

return number_of_decoded_bytes;

Expand Down Expand Up @@ -722,4 +733,3 @@ EipUint16 GetEncapsulationInactivityTimeout(CipInstance *instance) {
EipUint16 encapsulation_inactivity_timeout = *data;
return encapsulation_inactivity_timeout;
}