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Add a new flow risk about literal IP addresses used as SNI #1892

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Mar 2, 2023
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Add a new flow risk about literal IP addresses used as SNI #1892

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4 changes: 2 additions & 2 deletions doc/flow_risks.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -73,9 +73,9 @@ HTTP only: this risk is triggered whenever the user agent contains suspicious ch

.. _Risk 012:

NDPI_HTTP_NUMERIC_IP_HOST
NDPI_NUMERIC_IP_HOST
=========================
HTTP only: this risk is triggered whenever we're accessing a host using its IP rather than its symbolic name. Example http://1.2.3.4.
This risk is triggered whenever a HTTP/TLS/QUIC connection is using a literal IPv4 or IPv6 address as ServerName (TLS/QUIC; example: SNI=1.2.3.4) or as Hostname (HTTP; example: http://1.2.3.4.).

.. _Risk 013:

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2 changes: 1 addition & 1 deletion src/include/ndpi_typedefs.h
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Expand Up @@ -83,7 +83,7 @@ typedef enum {
NDPI_TLS_CERTIFICATE_EXPIRED,
NDPI_TLS_CERTIFICATE_MISMATCH, /* 10 */
NDPI_HTTP_SUSPICIOUS_USER_AGENT,
NDPI_HTTP_NUMERIC_IP_HOST,
NDPI_NUMERIC_IP_HOST,
NDPI_HTTP_SUSPICIOUS_URL,
NDPI_HTTP_SUSPICIOUS_HEADER,
NDPI_TLS_NOT_CARRYING_HTTPS,
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4 changes: 2 additions & 2 deletions src/lib/ndpi_main.c
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Expand Up @@ -142,7 +142,7 @@ static ndpi_risk_info ndpi_known_risks[] = {
{ NDPI_TLS_CERTIFICATE_EXPIRED, NDPI_RISK_HIGH, CLIENT_LOW_RISK_PERCENTAGE, NDPI_SERVER_ACCOUNTABLE },
{ NDPI_TLS_CERTIFICATE_MISMATCH, NDPI_RISK_HIGH, CLIENT_FAIR_RISK_PERCENTAGE, NDPI_SERVER_ACCOUNTABLE },
{ NDPI_HTTP_SUSPICIOUS_USER_AGENT, NDPI_RISK_HIGH, CLIENT_HIGH_RISK_PERCENTAGE, NDPI_CLIENT_ACCOUNTABLE },
{ NDPI_HTTP_NUMERIC_IP_HOST, NDPI_RISK_LOW, CLIENT_FAIR_RISK_PERCENTAGE, NDPI_CLIENT_ACCOUNTABLE },
{ NDPI_NUMERIC_IP_HOST, NDPI_RISK_LOW, CLIENT_FAIR_RISK_PERCENTAGE, NDPI_CLIENT_ACCOUNTABLE },
{ NDPI_HTTP_SUSPICIOUS_URL, NDPI_RISK_HIGH, CLIENT_HIGH_RISK_PERCENTAGE, NDPI_CLIENT_ACCOUNTABLE },
{ NDPI_HTTP_SUSPICIOUS_HEADER, NDPI_RISK_HIGH, CLIENT_HIGH_RISK_PERCENTAGE, NDPI_CLIENT_ACCOUNTABLE },
{ NDPI_TLS_NOT_CARRYING_HTTPS, NDPI_RISK_LOW, CLIENT_FAIR_RISK_PERCENTAGE, NDPI_CLIENT_ACCOUNTABLE },
Expand Down Expand Up @@ -2946,7 +2946,7 @@ static void ndpi_add_domain_risk_exceptions(struct ndpi_detection_module_struct
const ndpi_risk risks_to_mask[] = {
NDPI_SUSPICIOUS_DGA_DOMAIN,
NDPI_BINARY_APPLICATION_TRANSFER,
NDPI_HTTP_NUMERIC_IP_HOST,
NDPI_NUMERIC_IP_HOST,
NDPI_MALICIOUS_JA3,
NDPI_NO_RISK /* End */
};
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6 changes: 3 additions & 3 deletions src/lib/ndpi_utils.c
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Expand Up @@ -1928,8 +1928,8 @@ const char* ndpi_risk2str(ndpi_risk_enum risk) {
case NDPI_HTTP_SUSPICIOUS_USER_AGENT:
return("HTTP Susp User-Agent");

case NDPI_HTTP_NUMERIC_IP_HOST:
return("HTTP Numeric IP");
case NDPI_NUMERIC_IP_HOST:
return("HTTP/TLS/QUIC Numeric Hostname/SNI");

case NDPI_HTTP_SUSPICIOUS_URL:
return("HTTP Susp URL");
Expand Down Expand Up @@ -2053,7 +2053,7 @@ const char* ndpi_risk2str(ndpi_risk_enum risk) {

case NDPI_TCP_ISSUES:
return("TCP Connection Issues");

default:
ndpi_snprintf(buf, sizeof(buf), "%d", (int)risk);
return(buf);
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4 changes: 2 additions & 2 deletions src/lib/protocols/http.c
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Expand Up @@ -634,7 +634,7 @@ static void ndpi_check_numeric_ip(struct ndpi_detection_module_struct *ndpi_stru
char str[64];

snprintf(str, sizeof(str), "Found host %s", buf);
ndpi_set_risk(ndpi_struct, flow, NDPI_HTTP_NUMERIC_IP_HOST, str);
ndpi_set_risk(ndpi_struct, flow, NDPI_NUMERIC_IP_HOST, str);
}
}

Expand Down Expand Up @@ -916,7 +916,7 @@ static void check_content_type_and_change_protocol(struct ndpi_detection_module_
strstr(flow->http.url, "download.windowsupdate.com/")) &&
ndpi_strnstr((const char *)packet->user_agent_line.ptr, "Microsoft-Delivery-Optimization/",
packet->user_agent_line.len) &&
ndpi_isset_risk(ndpi_struct, flow, NDPI_HTTP_NUMERIC_IP_HOST)) {
ndpi_isset_risk(ndpi_struct, flow, NDPI_NUMERIC_IP_HOST)) {
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_WINDOWS_UPDATE, NDPI_PROTOCOL_HTTP, NDPI_CONFIDENCE_DPI);
}
}
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24 changes: 23 additions & 1 deletion src/lib/protocols/tls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -347,6 +347,7 @@ static void checkTLSSubprotocol(struct ndpi_detection_module_struct *ndpi_struct
ndpi_set_detected_protocol(ndpi_struct, flow, cached_proto, __get_master(ndpi_struct, flow), NDPI_CONFIDENCE_DPI_CACHE);
flow->category = ndpi_get_proto_category(ndpi_struct, ret);
ndpi_check_subprotocol_risk(ndpi_struct, flow, cached_proto);
ndpi_unset_risk(ndpi_struct, flow, NDPI_NUMERIC_IP_HOST);
}
}
}
Expand Down Expand Up @@ -682,8 +683,10 @@ static void processCertificateElements(struct ndpi_detection_module_struct *ndpi
}

if(!flow->protos.tls_quic.subprotocol_detected)
if(ndpi_match_hostname_protocol(ndpi_struct, flow, __get_master(ndpi_struct, flow), dNSName, dNSName_len))
if(ndpi_match_hostname_protocol(ndpi_struct, flow, __get_master(ndpi_struct, flow), dNSName, dNSName_len)) {
flow->protos.tls_quic.subprotocol_detected = 1;
ndpi_unset_risk(ndpi_struct, flow, NDPI_NUMERIC_IP_HOST);
}

i += len;
} else {
Expand Down Expand Up @@ -727,6 +730,7 @@ static void processCertificateElements(struct ndpi_detection_module_struct *ndpi
ndpi_set_detected_protocol(ndpi_struct, flow, proto_id, __get_master(ndpi_struct, flow), NDPI_CONFIDENCE_DPI);
flow->category = ndpi_get_proto_category(ndpi_struct, ret);
ndpi_check_subprotocol_risk(ndpi_struct, flow, proto_id);
ndpi_unset_risk(ndpi_struct, flow, NDPI_NUMERIC_IP_HOST);

if(ndpi_struct->tls_cert_cache) {
u_int32_t key = make_tls_cert_key(packet, 0 /* from the server */);
Expand Down Expand Up @@ -1506,6 +1510,19 @@ static void checkExtensions(struct ndpi_detection_module_struct *ndpi_struct,
}
}

/* **************************************** */

static int check_sni_is_numeric_ip(char *sni) {
unsigned char buf[sizeof(struct in6_addr)];

if(inet_pton(AF_INET, sni, buf) == 1)
return 1;
if(inet_pton(AF_INET6, sni, buf) == 1)
return 1;
return 0;
}


/* **************************************** */

int processClientServerHello(struct ndpi_detection_module_struct *ndpi_struct,
Expand Down Expand Up @@ -2050,6 +2067,11 @@ int processClientServerHello(struct ndpi_detection_module_struct *ndpi_struct,
flow->protos.tls_quic.subprotocol_detected = 1;
}

if(flow->protos.tls_quic.subprotocol_detected == 0 &&
check_sni_is_numeric_ip(sni) == 1) {
ndpi_set_risk(ndpi_struct, flow, NDPI_NUMERIC_IP_HOST, sni);
}

if(ndpi_check_dga_name(ndpi_struct, flow,
sni, 1, 0)) {
#ifdef DEBUG_TLS
Expand Down
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