Security
and
Privacy
This
page
is
part
of
the
FHIR
Specification
(v3.0.2:
STU
3).
(v3.3.0:
R4
Ballot
2).
The
current
version
which
supercedes
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FHIR
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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:
Time
critical
concerns
regarding
security
flaws
in
the
FHIR
specification
should
be
addressed
to
the
FHIR
email
list
for
prompt
consideration.
Implementers
should
track
the
developing
IHE
IUA
Profile
for
additional
security
considerations.
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
.
The
Service
Base
URL
will
specify
whether
SSL
is
required.
Client
authentication
may
be
required
by
the
server,
possibly
including
the
requirement
for
client
certificates.
TLS/SSL SHOULD be used for all production data exchange. The TLS/SSL communications are established prior to any HTTP command/response, so the whole FHIR interaction is protected by the SSL/TLS communications. The security of the endpoints of the TLS/SSL 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
support
browser-based
client
applications,
servers
SHOULD
implement
cross-origin
resource
sharing
for
the
REST
operations
.
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,
OpenID
Connect
may
be
used
to
authenticate
users
and
OAuth
may
be
used
to
authenticate
and/or
authorize
the
users.
The
Smart-On-FHIR
profile
on
OAuth
is
tightly
integrated
with
FHIR
and
is
the
preferred
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.
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.
This
specification
recommends
the
use
of
W3C
Digital
Signatures
for
signatures.
Resources
can
be
signed
using
the
Provenance
resource
to
carry
a
detached
digital
signature
.
The
Signature
datatype
is
available
to
support
various
signature
types
including
non-repudiation
purposes.
Further
details
on
creation
and
validation
of
Signatures
are
defined.
In
addition,
documents
may
be
signed
using
an
enveloped
signature.
A
specification
for
enveloped
signature
is
profiled
in
the
IHE
DSG
profile
.
Neither of these definitions prohibits the use of other ways of using digital signatures.
STU Note: the use of signatures with RESTful interfaces is a poorly understood area, and we would welcome reports of implementation experience. See discussion on use of Digital Signature in FHIR
Feedback is welcome here
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
(v3.3.0-13671)
generated
on
Thurs,
Oct
24,
2019
11:53+1100.
Tue,
Apr
3,
2018
12:19+1000.
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