Security
and
Privacy
This
page
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part
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the
FHIR
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(v3.0.2:
STU
3).
(v3.5.0:
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Maturity Level : 4 | Ballot Status : Trial Use |
Fast Healthcare Interoperability Resources (FHIR) is not a security protocol, nor does it define any security related functionality. However, FHIR does define exchange protocols and content models that need to be used with various security protocols defined elsewhere. This section gathers all information about security in one section. A summary:
where
appropriate.
Time
critical
concerns
regarding
security
flaws
in
the
FHIR
specification
should
be
addressed
to
the
FHIR
email
list
for
prompt
consideration.
A production FHIR system will need some kind of security sub-system that administers users, user authentication, and user authorization. Where this subsystem fits into the deployment architecture is a matter for system design:
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In this diagram, the red lines represent FHIR interfaces. From the perspective of the FHIR API, the client (consumer of FHIR services) may either interact with a security system that manifests as a FHIR server, and which depends on a subsequent FHIR interface to provide the actual storage, or either the client or server interacts with the security system independently. In each of these 3 scenarios, the different components may be assembled into applications or network components differently, but the same logical layout applies. The FHIR specification assumes that a security system exists, and that it may be deployed in front of or behind the FHIR API.
The security system includes the following subsystems:
Because there are a plethora of standards relating to the administration and functionality of the security system, FHIR does not provide user, profile, or other such administration resources. Instead, the FHIR resources are the targets of the policies expressed in these other approaches. What FHIR does specify is a way to apply security labels to resources so that a security system may use these (along with the contents of the resources if appropriate) to determine whether a user is authorized to perform a particular FHIR operation or not.
For
the
RESTful
API
,
normal
HTTP
security
rules
apply.
Please
follow
the
HTTP
specification
Security
Considerations
section
15
9
.
The
Service
Base
URL
will
specify
whether
SSL
TLS
is
required.
Client
authentication
may
be
required
by
the
server,
possibly
including
the
requirement
for
client
certificates.
When
returning
responses
to
non-authorized
clients,
ensure
that
Hypertext
Transfer
Protocol
(HTTP)
headers
of
a
web
server
and
API
error
messages
or
faults
do
not
disclose
detailed
information
about
the
underlying
web
server
that
could
be
the
source
of
potential
exploitation.
TLS/SSL
SHOULD
Please
follow
IETF
Best
Current
Practice
(
BCP
195
)
-
"Recommendations
for
Secure
Use
of
Transport
Layer
Security
(TLS)
and
Datagram
Layer
Security
(DTLS)"
.
This
recommends
TLS
1.2
or
higher
be
used
for
all
production
data
exchange.
exchange,
limits
support
for
lower
versions
of
TLS,
and
forbids
SSL.
Versions
of
TLS
prior
to
TLS
1.2
should
be
used
only
where
TLS
1.2
or
higher
is
not
available
between
partners.
When
using
TLS,
use
with
strong
cipher
suites
(e.g.
AES).
Consider using additional methods of security for an API to help authenticate where Domain Name System (DNS) responses are coming from and ensure that they are valid. For example, the use of Domain Name System Security Extensions (DNSSEC), a suite of extensions that add security to the DNS protocol, can ensure that domains associated with API endpoints that transmit health information or information required for API access are secure. DNSSEC provides origin authority, data integrity, and authenticated denial of existence. With DNSSEC, the DNS protocol is much less susceptible to certain types of attacks, particularly DNS spoofing attacks.
The
TLS/SSL
TLS
communications
are
established
prior
to
any
HTTP
command/response,
so
the
whole
FHIR
interaction
is
protected
by
the
SSL/TLS
TLS
communications.
The
security
of
the
endpoints
of
the
TLS/SSL
TLS
communications
must
be
risk-managed,
so
as
to
prevent
inappropriate
risks
(e.g.
audit
logging
of
the
GET
parameters
into
an
unprotected
audit
log).
To
When
it
is
desireable
to
support
browser-based
javascript
client
applications,
servers
SHOULD
implement
consider
enabling
cross-origin
resource
sharing
(CORS)
for
the
REST
operations
.
Consider
advice
from
sources
includeing
Enable-CORS
and
Moesif
blog
on
Guide
to
CORS
Pitfalls
.
Experience
shows
that
this
is
an
area
where
ongoing
issues
may
be
expected
as
security
holes
are
found
and
closed
on
an
ongoing
basis.
Other
than
testing
systems,
FHIR
servers
should
authenticate
the
clients.
The
server
may
choose
to
authenticate
the
client
system
and
trust
it,
or
to
authenticate
the
individual
user
by
a
variety
of
techniques.
For
web-centric
use,
environments
it
is
recommended
to
use
OpenID
Connect
may
(or
other
suitable
authentication
protocol)
to
verify
identity
of
the
end
user,
where
it
is
necessary
that
end-users
be
used
identified
to
authenticate
users
and
the
application.
It
is
recommended
that
OAuth
may
be
used
to
authenticate
and/or
authorize
the
users.
client
and
user.
The
Smart-On-FHIR
profile
on
OAuth
is
tightly
integrated
with
FHIR
and
is
the
preferred
a
recommended
method
for
using
OAuth.
The
HEART
Working
Group
has
developed
a
set
of
privacy
and
security
specifications
that
enable
an
individual
to
control
the
authorization
of
access
to
RESTful
health-related
data
sharing
APIs,
and
to
facilitate
the
development
of
interoperable
implementations
of
these
specifications
by
others.
IHE
IUA
Profile
constrains
OAuth
token
attributes
to
support
Healthcare.
All systems are shall protect authenticator mechanisms, and select the type of credential/strength of authenticator based on use-case and risk management.
Correctly identifying people, devices, locations and organizations is one of the foundations that any security system is built on. Most applications of security protocols, whether authentication, access control, digital signatures, etc. rely on the correct mapping between the relevant resources and the underlying systems. Note that this isn't necessary. There is nothing in FHIR that requires or relies on any security being in place, or any particular implementation. However, real world usage will generally require this.
A holder of data should not allow the data to be communicated unless there are sufficient assurances that the other party is authorized to receive it. This is true for a client creating a resource through a PUT/POST, as much as it is true for a server returning resources on a GET. The presumption is that without proper authorization, to the satisfaction of the data holder, the data does not get communicated.
Two of the classic Access Control models are: Role-Based Access Control (RBAC), and Attribute-Based Access Control (ABAC).
In Role-Based Access Control (RBAC), permissions are operations on an object that a user wishes to access. Permissions are grouped into roles. A role characterizes the functions a user is allowed to perform. Roles are assigned to users. If the user’s role has the appropriate permissions to access an object, then that user is granted access to the object. FHIR readily enables RBAC, as FHIR Resources are object types and the CRUDE (Create, Read, Update, Delete, Execute) events (the FHIR equivalent to permissions in the RBAC scheme) are operations on those objects.
In Attribute-Based Access Control (ABAC), a user requests to perform operations on objects. That user's access request is granted or denied based on a set of access control policies that are specified in terms of attributes and conditions. FHIR readily enables ABAC, as instances of a Resource in FHIR (again, Resources are object types) can have attributes associated with them. These attributes include security tags, environment conditions, and a host of user and object characteristics, which are the same attributes as those used in ABAC. Attributes help define the access control policies that determine the operations a user may perform on a Resource (in FHIR) or object (in ABAC). For example, a tag (or attribute) may specify that the identified Resource (object) is not to be further disclosed without explicit consent from the patient.
The rules behind the access control decision are often very complex, and potentially depend on information sourced from:
For
one
source
of
further
information,
see
the
IHE
Access
Control
white
paper
Access control constraints may result in data returned in a read or search being redacted or otherwise restricted. See Variations between Submitted data and Retrieved data .
A web-server, especially hosting FHIR, must choose the response carefully when an Access Denied condition exists. Returning too much information may expose details that should not be communicated. The Access Denied condition might be because of missing but required Authentication, the user is not authorized to access the endpoint, the user is not authorized to access specific data, or other policy reasons.
To balance usability of the returned result vs appropriate protection, the actual result method used needs to be controlled by policy and context. Typical methods of handling Access Denied used are:
Return
a
Success
with
Bundle
containing
zero
results
–
This
result
is
indistinguishable
from
the
case
where
no
data
is
known.
When
consistently
returned
on
Access
Denied,
this
will
not
expose
which
patients
exist,
or
what
data
might
be
blinded.
This
method
is
also
consistent
with
cases
where
some
results
are
authorized
while
other
results
are
blinded.
This
can
only
be
used
when
the
returning
a
Bundle
is
a
valid
result.
Return a 404 “Not Found” – This also protects from data leakage as it is indistinguishable from a query against a resource that doesn’t exist. It does however leak that the user authentication is validated.
Return a 403 “Forbidden” – This communicates that the reason for the failure is an Authorization failure. It should only be used when the client and/or user is well enough known to be given this information. Thus this method is most used when the user is allowed to know that they are forbidden access. It doesn’t explain how the user might change things to become authorized.
Return a 401 “Unauthorized” – This communicates that user authentication was attempted and failed to be authenticated.
Note that if a server allows PUT to a new location , it is not feasible to return 404 Not Found. This means that clients can use this to test whether content exists that they are not able to access, which is a minor, but potentially significant, leak of information.
FHIR provides an AuditEvent resource suitable for use by FHIR clients and servers to record when a security or privacy relevant event has occurred. This form of audit logging records as much detail as reasonable at the time the event happened.
When
used
to
record
security
and
privacy
relevant
events,
the
AuditEvent
can
then
be
used
by
properly
authorized
applications
to
support
audit
reporting,
alerting,
filtering,
and
forwarding.
This
model
has
been
developed
and
used
in
healthcare
for
a
decade
as
IHE-ATNA
profile
.
ATNA
log
events
can
be
automatically
converted
to
AuditEvent
resources,
and
from
there,
client
applications
are
able
to
search
the
audit
events,
or
subscribe
to
them.
With regard to HTTP logs, implementers need to consider the implications of distributing access to the logs. HTTP logs, including those that only contain the URL itself, should be regarded as being as sensitive as the resources themselves. Even if direct PHI is kept out of the logs by careful avoidance of search parameters (e.g. by using POST), the logs will still contain a rich set of information about the clinical records.
Several FHIR resources include attachments. Attachments can either be references to content found elsewhere or included inline encoded in base64. Attachments represent security risks in a way that FHIR resources do not, since some attachments contain executable code. Implementers should always use caution when handling resources.
See Security Labels .
FHIR
resources
include
an
XHTML
narrative,
so
that
applications
can
display
the
contents
of
the
resource
to
users
without
having
to
fully
and
correctly
process
the
data
in
the
resource.
However,
displaying
HTML
is
associated
with
several
known
security
issues
that
have
been
observed
in
production
systems
in
other
contexts
(e.g.
with
CDA
).
For
this
reason,
the
FHIR
narrative
is
not
allowed
to
contain
active
content
.
However,
care
is
still
needed
when
displaying
the
narrative:
Also note that the inclusion of an external reference to an image can allow the server that hosts the image to track when the resource is displayed. This may be a feature or a problem depending on the context.
In addition to narrative, Documents may also contain stylesheets. Unlike with CDA, the stylesheets are simple CSS stylesheets, not executable XSLT, so the same security risks do not apply. However CSS stylesheets may still reference external content (e.g. background images), and applications displaying documents should ensure that CSS links are not automatically followed without checking their safety first, and that session/identifying information does not leak with any use of external links.
®©
HL7.org
2011+.
FHIR
Release
3
(STU;
v3.0.2-11200)
Mixed
Nomative/Trial
Use
Ballot
#2
(v3.5.0-14907)
generated
on
Thurs,
Oct
24,
2019
11:53+1100.
Sun,
Aug
19,
2018
21:54+1000.
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