Access-lists and firewall rules

This category of questions allows you to analyze the behavior of access control lists and firewall rules. It also allows you to comprehensively validate (aka verification) that some traffic is or is not allowed.

• Filter Line Reachability

• Search Filters

• Test Filters

• Find Matching Filter Lines

Filter Line Reachability

Returns unreachable lines in filters (ACLs and firewall rules).

Finds all lines in the specified filters that will not match any packet, either because of being shadowed by prior lines or because of its match condition being empty.

Inputs

Name	Description	Type	Optional	Default Value
nodes	Examine filters on nodes matching this specifier.	NodeSpec	True
filters	Specifier for filters to test.	FilterSpec	True
ignoreComposites	Whether to ignore filters that are composed of multiple filters defined in the configs.	bool	True	False

Invocation

result = bf.q.filterLineReachability().answer().frame()

Return Value

Name	Description	Type
Sources	Filter sources	List of str
Unreachable_Line	Filter line that cannot be matched (i.e., unreachable)	str
Unreachable_Line_Action	Action performed by the unreachable line (e.g., PERMIT or DENY)	str
Blocking_Lines	Lines that, when combined, cover the unreachable line	List of str
Different_Action	Whether unreachable line has an action different from the blocking line(s)	bool
Reason	The reason a line is unreachable	str
Additional_Info	Additional information	str

Print the first 5 rows of the returned Dataframe

result.head(5)

	Sources	Unreachable_Line	Unreachable_Line_Action	Blocking_Lines	Different_Action	Reason	Additional_Info
0	['as2dept1: RESTRICT_HOST_TRAFFIC_OUT']	deny ip 1.128.0.0 0.0.255.255 2.128.0.0 0.0.255.255	DENY	['permit ip any 2.128.0.0 0.0.255.255']	True	BLOCKING_LINES	None
1	['as2dept1: RESTRICT_HOST_TRAFFIC_IN']	permit icmp any any	PERMIT	['deny ip any any']	True	BLOCKING_LINES	None

Print the first row of the returned Dataframe

result.iloc[0]

Sources                                  ['as2dept1: RESTRICT_HOST_TRAFFIC_OUT']
Unreachable_Line           deny   ip 1.128.0.0 0.0.255.255 2.128.0.0 0.0.255.255
Unreachable_Line_Action                                                     DENY
Blocking_Lines                           ['permit ip any 2.128.0.0 0.0.255.255']
Different_Action                                                            True
Reason                                                            BLOCKING_LINES
Additional_Info                                                             None
Name: 0, dtype: object

Search Filters

Finds flows for which a filter takes a particular behavior.

This question searches for flows for which a filter (access control list) has a particular behavior. The behaviors can be: that the filter permits the flow (permit), that it denies the flow (deny), or that the flow is matched by a particular line (matchLine <lineNumber>). Filters are selected using node and filter specifiers, which might match multiple filters. In this case, a (possibly different) flow will be found for each filter.

Inputs

Name	Description	Type	Optional	Default Value
nodes	Only evaluate filters present on nodes matching this specifier.	NodeSpec	True
filters	Only evaluate filters that match this specifier.	FilterSpec	True
headers	Packet header constraints on the flows being searched.	HeaderConstraints	True
action	The behavior that you want evaluated. Specify exactly one of permit, deny, or matchLine <line number>.	str	True
startLocation	Only consider specified locations as possible sources.	LocationSpec	True
invertSearch	Search for packet headers outside the specified headerspace, rather than inside the space.	bool	True

Invocation

result = bf.q.searchFilters(headers=HeaderConstraints(srcIps='10.10.10.0/24', dstIps='218.8.104.58', applications = ['dns']), action='deny', filters='acl_in').answer().frame()

Return Value

Name	Description	Type
Node	Node	str
Filter_Name	Filter name	str
Flow	Evaluated flow	Flow
Action	Outcome	str
Line_Content	Line content	str
Trace	ACL trace	List of TraceTree

Print the first 5 rows of the returned Dataframe

result.head(5)

	Node	Filter_Name	Flow	Action	Line_Content	Trace
0	rtr-with-acl	acl_in	start=rtr-with-acl [10.10.10.42:49152->218.8.104.58:53 UDP]	DENY	460 deny udp 10.10.10.42/32 218.8.104.58/32 eq domain	- Matched line 460 deny udp 10.10.10.42/32 218.8.104.58/32 eq domain

Print the first row of the returned Dataframe

result.iloc[0]

Node                                                                    rtr-with-acl
Filter_Name                                                                   acl_in
Flow                     start=rtr-with-acl [10.10.10.42:49152->218.8.104.58:53 UDP]
Action                                                                          DENY
Line_Content                   460 deny udp 10.10.10.42/32 218.8.104.58/32 eq domain
Trace           - Matched line 460 deny udp 10.10.10.42/32 218.8.104.58/32 eq domain
Name: 0, dtype: object

Test Filters

Returns how a flow is processed by a filter (ACLs, firewall rules).

Shows how the specified flow is processed through the specified filters, returning its permit/deny status as well as the line(s) it matched.

Inputs

Name	Description	Type	Optional	Default Value
nodes	Only examine filters on nodes matching this specifier.	NodeSpec	True
filters	Only consider filters that match this specifier.	FilterSpec	True
headers	Packet header constraints.	HeaderConstraints	False
startLocation	Location to start tracing from.	LocationSpec	True

Invocation

result = bf.q.testFilters(headers=HeaderConstraints(srcIps='10.10.10.1', dstIps='218.8.104.58', applications = ['dns']), nodes='rtr-with-acl', filters='acl_in').answer().frame()

Return Value

Name	Description	Type
Node	Node	str
Filter_Name	Filter name	str
Flow	Evaluated flow	Flow
Action	Outcome	str
Line_Content	Line content	str
Trace	ACL trace	List of TraceTree

Print the first 5 rows of the returned Dataframe

result.head(5)

	Node	Filter_Name	Flow	Action	Line_Content	Trace
0	rtr-with-acl	acl_in	start=rtr-with-acl [10.10.10.1:49152->218.8.104.58:53 UDP]	PERMIT	660 permit udp 10.10.10.0/24 218.8.104.58/32 eq domain	- Matched line 660 permit udp 10.10.10.0/24 218.8.104.58/32 eq domain

Print the first row of the returned Dataframe

result.iloc[0]

Node                                                                     rtr-with-acl
Filter_Name                                                                    acl_in
Flow                       start=rtr-with-acl [10.10.10.1:49152->218.8.104.58:53 UDP]
Action                                                                         PERMIT
Line_Content                   660 permit udp 10.10.10.0/24 218.8.104.58/32 eq domain
Trace           - Matched line 660 permit udp 10.10.10.0/24 218.8.104.58/32 eq domain
Name: 0, dtype: object

Find Matching Filter Lines

Returns lines in filters (ACLs and firewall rules) that match any packet within the specified header constraints.

Finds all lines in the specified filters that match any packet within the specified header constraints.

Inputs

Name	Description	Type	Optional	Default Value
nodes	Examine filters on nodes matching this specifier.	NodeSpec	True
filters	Specifier for filters to check.	FilterSpec	True
headers	Packet header constraints for which to find matching filter lines.	HeaderConstraints	True
action	Show filter lines with this action. By default returns lines with either action.	str	True
ignoreComposites	Whether to ignore filters that are composed of multiple filters defined in the configs.	bool	True	False

Invocation

result = bf.q.findMatchingFilterLines(headers=HeaderConstraints(applications='DNS')).answer().frame()

Return Value

Name	Description	Type
Node	Node	str
Filter	Filter name	str
Line	Line text	str
Line_Index	Index of line	int
Action	Action performed by the line (e.g., PERMIT or DENY)	str

Print the first 5 rows of the returned Dataframe

result.head(5)

	Node	Filter	Line	Line_Index	Action
0	as1border1	101	permit ip host 1.0.1.0 host 255.255.255.0	0	PERMIT
1	as1border1	101	permit ip host 1.0.2.0 host 255.255.255.0	1	PERMIT
2	as1border1	102	permit ip host 2.0.0.0 host 255.0.0.0	0	PERMIT
3	as1border1	102	permit ip host 2.128.0.0 host 255.255.0.0	1	PERMIT
4	as1border1	103	permit ip host 3.0.1.0 host 255.255.255.0	0	PERMIT

Print the first row of the returned Dataframe

result.iloc[0]

Node                                         as1border1
Filter                                              101
Line          permit ip host 1.0.1.0 host 255.255.255.0
Line_Index                                            0
Action                                           PERMIT
Name: 0, dtype: object