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TD0166:  Optional Authentication of TLS Client

Publication Date
2017.04.05

Protection Profiles
PP_BASE_VIRTUALIZATION_V1.0, PP_CA_v2.0

Other References
FCS_TLSC_EXT.1

Issue Description

Under normal deployment, a TLS client is seldom provisioned with a client certificate. Specifically, the management network (including audit server and authentication server) is usually trusted, and an authorized user's access to the TOE is controlled and the TOE is protected from unauthorized modification. It is not necessary to require that TLS client be provisioned with a client certificate and "be capable of presenting a certificate to a TLS server for TLS mutual authentication.  

In addition, test 5 bullet 4 for FCS_TLSC_EXT.1.1 and FCS_TLSC_EXT.2.1 and test 4 bullet 2 FCS_TLSS_EXT.1.1 and FCS_TLSS_EXT.2.1 can only be performed for cyphersuites that utilize Diffie Hellman.  These test should be conditional and only required when a ciphersuite that utilizes Diffie Hellman is claimed by a Security Target.

 

Resolution

FCS_TLSC_EXT.1 TLS Client Protocol is split into two separate requirements: FCS_TLSC_EXT.1 TLS Client Protocol and FCS_TLSC_EXT.2 TLS Client Protocol with Mutual Authentication.

FCS_TLSS_EXT.1.1 and FCS_TLSS_EXT.2.1 Test 4 Bullet 2 are also modified.

The modified requirements are as follows:

FCS_TLSC_EXT.1 TLS Client Protocol

FCS_TLSC_EXT.1.1           The TSF shall implement [selection: TLS 1.2 (RFC 5246), TLS 1.1 (RFC 4346)] supporting the following ciphersuites:

  •        Mandatory Ciphersuites:

 o        TLS_RSA_WITH_AES_128_CBC_SHA as defined in RFC 3268

  •       Optional Ciphersuites: [selection:

 o        TLS_RSA_WITH_AES_256_CBC_SHA as defined in RFC 3268

 o        TLS_DHE_RSA_WITH_AES_128_CBC_SHA as defined in RFC 3268

 o        TLS_DHE_RSA_WITH_AES_256_CBC_SHA as defined in RFC 3268

 o        TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA as defined in RFC 4492

 o        TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA as defined in RFC 4492

 o        TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA as defined in RFC 4492

 o        TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA as defined in RFC 4492

 o        TLS_RSA_WITH_AES_128_CBC_SHA256 as defined in RFC 5246

 o        TLS_RSA_WITH_AES_256_CBC_ SHA256 as defined in RFC 5246

 o        TLS_DHE_RSA_WITH_AES_128_CBC_ SHA256 as defined in RFC 5246

 o        TLS_DHE_RSA_WITH_AES_256_CBC_ SHA256 as defined in RFC 5246

 o        TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 as defined in RFC 5289

 o        TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 as defined in RFC 5289

 o        TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 as defined in RFC 5289

 o        TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 as defined in RFC 5289

 o        TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 as defined in RFC 5289

 o        TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 as defined in RFC 5289

 o        no other ciphersuite].

 

Application Note:            The ciphersuites to be tested in the evaluated configuration are limited by this requirement. The ST author should select the optional ciphersuites that are supported; if there are no ciphersuites supported other than the mandatory suites, then “None” should be selected. It is necessary to limit the ciphersuites that can be used in an evaluated configuration administratively on the server in the test environment. The Suite B algorithms listed above (RFC 6460) are the preferred algorithms for implementation. TLS_RSA_WITH_AES_128_CBC_SHA is required in order to ensure compliance with RFC 5246.

 These requirements will be revisited as new TLS versions are standardized by the IETF.

 If any ciphersuites are selected using ECDHE, then FCS_TLSC_EXT.1.4 is required.

 In a future version of this PP TLS v1.2 will be required for all TOEs.

 

Assurance Activity

The evaluator shall check the description of the implementation of this protocol in the TSS to ensure that the ciphersuites supported are specified. The evaluator shall check the TSS to ensure that the ciphersuites specified include those listed for this component.

Tests

Test 1: The evaluator shall establish a TLS connection using each of the ciphersuites specified by the requirement. This connection may be established as part of the establishment of a higher-level protocol, e.g., as part of an EAP session. It is sufficient to observe the successful negotiation of a ciphersuite to satisfy the intent of the test; it is not necessary to examine the characteristics of the encrypted traffic in an attempt to discern the ciphersuite being used (for example, that the cryptographic algorithm is 128-bit AES and not 256-bit AES).

Test 2: The evaluator shall attempt to establish the connection using a server with a server certificate that contains the Server Authentication purpose in the extendedKeyUsage field and verify that a connection is established. The evaluator will then verify that the client rejects an otherwise valid server certificate that lacks the Server Authentication purpose in the extendedKeyUsage field and a connection is not established. Ideally, the two certificates should be identical except for the extendedKeyUsage field.

Test 3: The evaluator shall send a server certificate in the TLS connection that the does not match the server-selected ciphersuite (for example, send a ECDSA certificate while using the TLS_RSA_WITH_AES_128_CBC_SHA ciphersuite or send a RSA certificate while using one of the ECDSA ciphersuites.) The evaluator shall verify that the TOE disconnects after receiving the server’s Certificate handshake message.

Test 4: The evaluator shall configure the server to select the TLS_NULL_WITH_NULL_NULL ciphersuite and verify that the client denies the connection.

Test 5: The evaluator shall perform the following modifications to the traffic:

·         Change the TLS version selected by the server in the Server Hello to a non-supported TLS version (for example 1.3 represented by the two bytes 03 04) and verify that the client rejects the connection.

·         Modify at least one byte in the server’s nonce in the Server Hello handshake message, and verify that the client rejects the Server Key Exchange handshake message (if using a DHE or ECDHE ciphersuite) or that the server denies the client’s Finished handshake message.

·         Modify the server’s selected ciphersuite in the Server Hello handshake message to be a ciphersuite not presented in the Client Hello handshake message. The evaluator shall verify that the client rejects the connection after receiving the Server Hello.

 

  • (conditional): If an ECDHE or DHE ciphersuite is selected, modify the signature block in the Server’s Key Exchange handshake message, and verify that the client rejects the connection after receiving the Server Key Exchange message.

 

·         Modify a byte in the Server Finished handshake message, and verify that the client sends a fatal alert upon receipt and does not send any application data.

·         Send a garbled message from the Server after the Server has issued the ChangeCipherSpec message and verify that the client denies the connection.

 

FCS_TLSC_EXT.1.2           The TSF shall verify that the presented identifier matches the reference identifier according to RFC 6125.

 

Application Note:            The rules for verification of identity are described in Section 6 of RFC 6125. The reference identifier is established by the user (e.g., entering a URL into a web browser or clicking a link), by configuration (e.g., configuring the name of a mail server or authentication server), or by an application (e.g., a parameter of an API) depending on the application service. Based on a singular reference identifier’s source domain and application service type (e.g., HTTP, SIP, LDAP), the client establishes all reference identifiers which are acceptable, such as a Common Name for the Subject Name field of the certificate and a (case-insensitive) DNS name, URI name, and Service Name for the Subject Alternative Name field. The client then compares this list of all acceptable reference identifiers to the presented identifiers in the TLS server’s certificate.

 

The preferred method for verification is the Subject Alternative Name using DNS names, URI names, or Service Names. Verification using the Common Name is required for the purposes of backwards compatibility. Additionally, support for use of IP addresses in the Subject Name or Subject Alternative name is discouraged as against best practices but may be implemented. Finally, the client should avoid constructing reference identifiers using wildcards. However, if the presented identifiers include wildcards, the client must follow the best practices regarding matching; these best practices are captured in the assurance activity.

 

Assurance Activity

The evaluator shall ensure that the TSS describes the client’s method of establishing all reference identifiers from the administrator/application-configured reference identifier, including which types of reference identifiers are supported (e.g., Common Name, DNS Name, URI Name, Service Name, or other application-specific Subject Alternative Names) and whether IP addresses and wildcards are supported. The evaluator shall ensure that this description identifies whether and the manner in which certificate pinning is supported or used by the TOE.

Tests

The evaluator shall configure the reference identifier according to the AGD guidance and perform the following tests during a TLS connection:

Test 1: The evaluator shall present a server certificate that does not contain an identifier in either the Subject Alternative Name (SAN) or Common Name (CN) that matches the reference identifier. The evaluator shall verify that the connection fails.

Test 2: The evaluator shall present a server certificate that contains a CN that matches the reference identifier, contains the SAN extension, but does not contain an identifier in the SAN that matches the reference identifier. The evaluator shall verify that the connection fails. The evaluator shall repeat this test for each supported SAN type.

Test 3: The evaluator shall present a server certificate that contains a CN that matches the reference identifier and does not contain the SAN extension. The evaluator shall verify that the connection succeeds.

Test 4: The evaluator shall present a server certificate that contains a CN that does not match the reference identifier but does contain an identifier in the SAN that matches. The evaluator shall verify that the connection succeeds.

Test 5: The evaluator shall perform the following wildcard tests with each supported type of reference identifier:

·         The evaluator shall present a server certificate containing a wildcard that is not in the left-most label of the presented identifier (e.g., foo.*.example.com) and verify that the connection fails.

·         The evaluator shall present a server certificate containing a wildcard in the left-most label (e.g., *.example.com). The evaluator shall configure the reference identifier with a single left-most label (e.g., foo.example.com) and verify that the connection succeeds. The evaluator shall configure the reference identifier without a left-most label as in the certificate (e.g., example.com) and verify that the connection fails. The evaluator shall configure the reference identifier with two left-most labels (e.g., bar.foo.example.come) and verify that the connection fails.

Test 6: [conditional] If URI or Service name reference identifiers are supported, the evaluator shall configure the DNS name and the service identifier. The evaluator shall present a server certificate containing the correct DNS name and service identifier in the URIName or SRVName fields of the SAN and verify that the connection succeeds. The evaluator shall repeat this test with the wrong service identifier (but correct DNS name) and verify that the connection fails.

Test 7: [conditional] If pinned certificates are supported the evaluator shall present a certificate that does not match the pinned certificate and verify that the connection fails.

 

FCS_TLSC_EXT.1.3           The TSF shall establish a trusted channel only if the peer certificate is valid.

 

Application Note:            Validity is determined by the identifier verification, certificate path, the expiration date, and the revocation status in accordance with RFC 5280. Certificate validity shall be tested in accordance with testing performed for FIA_X509_EXT.1.

 

Assurance Activity

Tests

Test 1: The evaluator shall demonstrate that using a certificate without a valid certification path results in the function failing. Using the administrative guidance, the evaluator shall then load a certificate or certificates needed to validate the certificate to be used in the function, and demonstrate that the function succeeds. The evaluator then shall delete one of the certificates, and show that the function fails.

 

FCS_TLSC_EXT.1.4          The TSF shall present the Supported Elliptic Curves Extension in the Client Hello with the following NIST curves: [selection: secp256r1, secp384r1, secp521r1] and no other curves.

 

Application Note:            If ciphersuites with elliptic curves were selected in FCS_TLSC_EXT.1.1, this component is required.

 This requirement limits the elliptic curves allowed for authentication and key agreement to the NIST curves from FCS_COP.1(2) and FCS_CKM.1 and FCS_CKM.2. This extension is required for clients supporting Elliptic Curve ciphersuites.

 

Assurance Activity

The evaluator shall verify that TSS describes the Supported Elliptic Curves Extension and whether the required behavior is performed by default or may be configured.

Tests

Test 1: The evaluator shall configure the server to perform an ECDHE key exchange in the TLS connection using a non-supported curve (for example P-192) and shall verify that the TOE disconnects after receiving the server’s Key Exchange handshake message.

 

 

 

 

FCS_TLSC_EXT.2 TLS Client Protocol with Mutual Authentication

 

FCS_TLSC_EXT.2.1           The TSF shall implement [selection: TLS 1.2 (RFC 5246), TLS 1.1 (RFC 4346)] supporting the following ciphersuites:

  •        Mandatory Ciphersuites:

 o        TLS_RSA_WITH_AES_128_CBC_SHA as defined in RFC 3268

  •        Optional Ciphersuites: [selection:

 o        TLS_RSA_WITH_AES_256_CBC_SHA as defined in RFC 3268

 o        TLS_DHE_RSA_WITH_AES_128_CBC_SHA as defined in RFC 3268

 o        TLS_DHE_RSA_WITH_AES_256_CBC_SHA as defined in RFC 3268

 o        TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA as defined in RFC 4492

 o        TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA as defined in RFC 4492

 o        TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA as defined in RFC 4492

 o        TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA as defined in RFC 4492

 o        TLS_RSA_WITH_AES_128_CBC_SHA256 as defined in RFC 5246

 o        TLS_RSA_WITH_AES_256_CBC_ SHA256 as defined in RFC 5246

 o        TLS_DHE_RSA_WITH_AES_128_CBC_ SHA256 as defined in RFC 5246

 o        TLS_DHE_RSA_WITH_AES_256_CBC_ SHA256 as defined in RFC 5246

 o        TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 as defined in RFC 5289

 o        TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 as defined in RFC 5289

 o        TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 as defined in RFC 5289

 o        TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 as defined in RFC 5289

 o        TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 as defined in RFC 5289

 o        TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 as defined in RFC 5289

 o        no other ciphersuite].

 

Application Note:            The ciphersuites to be tested in the evaluated configuration are limited by this requirement. The ST author should select the optional ciphersuites that are supported; if there are no ciphersuites supported other than the mandatory suites, then “None” should be selected. It is necessary to limit the ciphersuites that can be used in an evaluated configuration administratively on the server in the test environment. The Suite B algorithms listed above (RFC 6460) are the preferred algorithms for implementation. TLS_RSA_WITH_AES_128_CBC_SHA is required in order to ensure compliance with RFC 5246.

 These requirements will be revisited as new TLS versions are standardized by the IETF.

 If any ciphersuites are selected using ECDHE, then FCS_TLSC_EXT.2.5 is required.

 In a future version of this PP TLS v1.2 will be required for all TOEs.

 

Assurance Activity

The evaluator shall check the description of the implementation of this protocol in the TSS to ensure that the ciphersuites supported are specified. The evaluator shall check the TSS to ensure that the ciphersuites specified include those listed for this component.

Tests

Test 1: The evaluator shall establish a TLS connection using each of the ciphersuites specified by the requirement. This connection may be established as part of the establishment of a higher-level protocol, e.g., as part of an EAP session. It is sufficient to observe the successful negotiation of a ciphersuite to satisfy the intent of the test; it is not necessary to examine the characteristics of the encrypted traffic in an attempt to discern the ciphersuite being used (for example, that the cryptographic algorithm is 128-bit AES and not 256-bit AES).

Test 2: The evaluator shall attempt to establish the connection using a server with a server certificate that contains the Server Authentication purpose in the extendedKeyUsage field and verify that a connection is established. The evaluator will then verify that the client rejects an otherwise valid server certificate that lacks the Server Authentication purpose in the extendedKeyUsage field and a connection is not established. Ideally, the two certificates should be identical except for the extendedKeyUsage field.

Test 3: The evaluator shall send a server certificate in the TLS connection that the does not match the server-selected ciphersuite (for example, send a ECDSA certificate while using the TLS_RSA_WITH_AES_128_CBC_SHA ciphersuite or send a RSA certificate while using one of the ECDSA ciphersuites.) The evaluator shall verify that the TOE disconnects after receiving the server’s Certificate handshake message.

Test 4: The evaluator shall configure the server to select the TLS_NULL_WITH_NULL_NULL ciphersuite and verify that the client denies the connection.

Test 5: The evaluator shall perform the following modifications to the traffic:

·         Change the TLS version selected by the server in the Server Hello to a non-supported TLS version (for example 1.3 represented by the two bytes 03 04) and verify that the client rejects the connection.

·         Modify at least one byte in the server’s nonce in the Server Hello handshake message, and verify that the client rejects the Server Key Exchange handshake message (if using a DHE or ECDHE ciphersuite) or that the server denies the client’s Finished handshake message.

·         Modify the server’s selected ciphersuite in the Server Hello handshake message to be a ciphersuite not presented in the Client Hello handshake message. The evaluator shall verify that the client rejects the connection after receiving the Server Hello.

 

  • (conditional): If an ECDHE or DHE ciphersuite is selected, modify the signature block in the Server’s Key Exchange handshake message, and verify that the client rejects the connection after receiving the Server Key Exchange message.

 

·         Modify a byte in the Server Finished handshake message, and verify that the client sends a fatal alert upon receipt and does not send any application data.

·         Send a garbled message from the Server after the Server has issued the ChangeCipherSpec message and verify that the client denies the connection.

 

FCS_TLSC_EXT.2.2           The TSF shall verify that the presented identifier matches the reference identifier according to RFC 6125.

 

Application Note:            The rules for verification of identity are described in Section 6 of RFC 6125. The reference identifier is established by the user (e.g., entering a URL into a web browser or clicking a link), by configuration (e.g., configuring the name of a mail server or authentication server), or by an application (e.g., a parameter of an API) depending on the application service. Based on a singular reference identifier’s source domain and application service type (e.g., HTTP, SIP, LDAP), the client establishes all reference identifiers which are acceptable, such as a Common Name for the Subject Name field of the certificate and a (case-insensitive) DNS name, URI name, and Service Name for the Subject Alternative Name field. The client then compares this list of all acceptable reference identifiers to the presented identifiers in the TLS server’s certificate.

 

The preferred method for verification is the Subject Alternative Name using DNS names, URI names, or Service Names. Verification using the Common Name is required for the purposes of backwards compatibility. Additionally, support for use of IP addresses in the Subject Name or Subject Alternative name is discouraged as against best practices but may be implemented. Finally, the client should avoid constructing reference identifiers using wildcards. However, if the presented identifiers include wildcards, the client must follow the best practices regarding matching; these best practices are captured in the assurance activity.

 

Assurance Activity

The evaluator shall ensure that the TSS describes the client’s method of establishing all reference identifiers from the administrator/application-configured reference identifier, including which types of reference identifiers are supported (e.g., Common Name, DNS Name, URI Name, Service Name, or other application-specific Subject Alternative Names) and whether IP addresses and wildcards are supported. The evaluator shall ensure that this description identifies whether and the manner in which certificate pinning is supported or used by the TOE.

Tests

The evaluator shall configure the reference identifier according to the AGD guidance and perform the following tests during a TLS connection:

Test 1: The evaluator shall present a server certificate that does not contain an identifier in either the Subject Alternative Name (SAN) or Common Name (CN) that matches the reference identifier. The evaluator shall verify that the connection fails.

Test 2: The evaluator shall present a server certificate that contains a CN that matches the reference identifier, contains the SAN extension, but does not contain an identifier in the SAN that matches the reference identifier. The evaluator shall verify that the connection fails. The evaluator shall repeat this test for each supported SAN type.

Test 3: The evaluator shall present a server certificate that contains a CN that matches the reference identifier and does not contain the SAN extension. The evaluator shall verify that the connection succeeds.

Test 4: The evaluator shall present a server certificate that contains a CN that does not match the reference identifier but does contain an identifier in the SAN that matches. The evaluator shall verify that the connection succeeds.

Test 5: The evaluator shall perform the following wildcard tests with each supported type of reference identifier:

·         The evaluator shall present a server certificate containing a wildcard that is not in the left-most label of the presented identifier (e.g., foo.*.example.com) and verify that the connection fails.

·         The evaluator shall present a server certificate containing a wildcard in the left-most label (e.g., *.example.com). The evaluator shall configure the reference identifier with a single left-most label (e.g., foo.example.com) and verify that the connection succeeds. The evaluator shall configure the reference identifier without a left-most label as in the certificate (e.g., example.com) and verify that the connection fails. The evaluator shall configure the reference identifier with two left-most labels (e.g., bar.foo.example.come) and verify that the connection fails.

Test 6: [conditional] If URI or Service name reference identifiers are supported, the evaluator shall configure the DNS name and the service identifier. The evaluator shall present a server certificate containing the correct DNS name and service identifier in the URIName or SRVName fields of the SAN and verify that the connection succeeds. The evaluator shall repeat this test with the wrong service identifier (but correct DNS name) and verify that the connection fails.

Test 7: [conditional] If pinned certificates are supported the evaluator shall present a certificate that does not match the pinned certificate and verify that the connection fails.

 

FCS_TLSC_EXT.2.3           The TSF shall establish a trusted channel only if the peer certificate is valid.

 

Application Note:            Validity is determined by the identifier verification, certificate path, the expiration date, and the revocation status in accordance with RFC 5280. Certificate validity shall be tested in accordance with testing performed for FIA_X509_EXT.1.

 

Assurance Activity

Tests

Test 1: The evaluator shall demonstrate that using a certificate without a valid certification path results in the function failing. Using the administrative guidance, the evaluator shall then load a certificate or certificates needed to validate the certificate to be used in the function, and demonstrate that the function succeeds. The evaluator then shall delete one of the certificates, and show that the function fails.

 

FCS_TLSC_EXT.2.4           The TSF shall support mutual authentication using X.509v3 certificates.

 

Application Note:            If TLS is used for FTP_ITC_EXT.1, then this component is required.

 

The use of X.509v3 certificates for TLS is addressed in FIA_X509_EXT.2.1. This requirement adds that this use must include the client must be capable of presenting a certificate to a TLS server for TLS mutual authentication.

 

Assurance Activity

The evaluator shall ensure that the TSS description required per FIA_X509_EXT.2.1 includes the use of client-side certificates for TLS mutual authentication.

Tests

Test 1: The evaluator shall perform the following modification to the traffic:

·         Configure the server to require mutual authentication and then modify a byte in a CA field in the Server’s Certificate Request handshake message. The modified CA field shall not be the CA used to sign the client’s certificate. The evaluator shall verify the connection is unsuccessful.

 

FCS_TLSC_EXT.2.5           The TSF shall present the Supported Elliptic Curves Extension in the Client Hello with the following NIST curves: [selection: secp256r1, secp384r1, secp521r1] and no other curves.

 

Application Note:            If ciphersuites with elliptic curves were selected in FCS_TLSC_EXT.2.1, this component is required.

 

This requirement limits the elliptic curves allowed for authentication and key agreement to the NIST curves from FCS_COP.1(2) and FCS_CKM.1 and FCS_CKM.2. This extension is required for clients supporting Elliptic Curve ciphersuites.

 

Assurance Activity

The evaluator shall verify that TSS describes the Supported Elliptic Curves Extension and whether the required behavior is performed by default or may be configured.

Tests

Test 1: The evaluator shall configure the server to perform an ECDHE key exchange in the TLS connection using a non-supported curve (for example P-192) and shall verify that the TOE disconnects after receiving the server’s Key Exchange handshake message.

 

 

Modified test activities for FCS_TLSS_EXT.1.1 and FCS_TLSS_EXT.2.1

 

Test 4, bullet 2 for FCS_TLSS_EXT.1.1 is updated as follows:

 

"(conditional): If an ECDHE or DHE ciphersuite is selected, modify the signature block in the Client’s Key Exchange handshake message, and verify that the server rejects the client’s Certificate Verify handshake message (if using mutual authentication) or that the server denies the client’s Finished handshake message."

 

 

 

Test 4, bullet 2 for FCS_TLSS_EXT.2.1 is updated as follows:

 

"(conditional): If an ECDHE or DHE ciphersuite is selected, modify the signature block in the Client’s Key Exchange handshake message, and verify that the server rejects the client’s Certificate Verify handshake message (if using mutual authentication) or that the server denies the client’s Finished handshake message."

 

Justification

TLS may or may not be performed with client authentication.

Tests for cyphersuites that utilize Diffie Hellman should be conditional.

 
 
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