Troubleshoot New Certificate Issues

CDO's Use of Certificates

CDO checks the validity of certificates when connecting to devices. Specifically, CDO requires that:

The device uses a TLS version equal to or greater than 1.0.
The certificate presented by the device is not expired, and its issuance date is in the past (i.e. it is already valid, not scheduled to become valid at a later date).
The certificate must be a SHA-256 certificate. SHA-1 certificates will not be accepted.
One of these conditions is true:
- The device uses a self-signed certificate, and it is the same as the most recent one trusted by an authorized user.
- The device uses a certificate signed by a trusted Certificate Authority (CA), and provides a certificate chain linking the presented leaf certificate to the relevant CA.

These are the ways CDO uses certificates differently than browsers:

In the case of self-signed certificates, CDO overrides the domain name check, instead checking that the certificate exactly matches the one trusted by an authorized user during device onboarding or reconnection.
CDO does not yet support internal CAs. There is currently no way to check a certificate signed by an internal CA.

It is possible to disable certificate checking for ASA devices on a per-device basis. When an ASA's certificate cannot be trusted by CDO, you will have the option of disabling certificate checking for that device. If you have attempted to disable certificate checking for the device and you are still unable to onboard it, it is likely that the IP address and port you specified for the device is incorrect or unreachable. There is no way to disable certificate checking globally, or to disable certificate checking for a device with a supported certificate. There is no way to disable certificate checking for non-ASA devices.

When you disable certificate checking for a device, CDO will still use TLS to connect to the device, but it will not validate the certificate used to establish the connection. This means that a passive man-in-the-middle attacker will not be able to eavesdrop on the connection, but an active man-in-the-middle could intercept the connection by supplying CDO with an invalid certificate.

Identifying Certificate Issues

There are several reasons that CDO may not be able to onboard a device. When the UI shows a message that "CDO cannot connect to the device using the certificate presented," there is a problem with the certificate. When the UI does not show this message, the problem is more likely related to connectivity problems (the device is unreachable) or other network errors.

To determine why CDO rejects a given certificate, you can use the openssl command-line tool on the SDC host or another host that can reach the relevant device. Use the following command to create a file showing the certificates presented by the device:

openssl s_client -showcerts -connect <host>:<port> &> <filename>.txt

This command will start an interactive session, so you will need to use Ctrl-c to exit after a couple of seconds.

You should now have a file containing output like the following:

depth=2 C = US, O = GeoTrust Inc., CN = GeoTrust Global CA 
verify return:1
depth=1 C = US, O = Google Inc, CN = Google Internet Authority G2 
verify return:1 
depth=0 C = US, ST = California, L = Mountain View, O = Google Inc, CN = *.google.com 
verify return:1 CONNECTED(00000003)
---
Certificate chain
0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=*.google.com 
  i:/C=US/O=Google Inc/CN=Google Internet Authority G2
-----BEGIN CERTIFICATE----- 
MIIH0DCCBrigAwIBAgIIUOMfH+8ftN8wDQYJKoZIhvcNAQELBQAwSTELMAkGA1UE 
....lots of base64... 
tzw9TylimhJpZcl4qihFVTgFM7rMU2VHulpJgA59gdbaO/Bf
-----END CERTIFICATE-----
1 s:/C=US/O=Google Inc/CN=Google Internet Authority G2 
  i:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA 
-----BEGIN CERTIFICATE----- 
MIID8DCCAtigAwIBAgIDAjqSMA0GCSqGSIb3DQEBCwUAMEIxCzAJBgNVBAYTAlVT 
....lots of base64... 
tzw9TylimhJpZcl4qihFVTgFM7rMU2VHulpJgA59gdbaO/Bf 
-----END CERTIFICATE----- 
2 s:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA 
  i:/C=US/O=Equifax/OU=Equifax Secure Certificate Authority 
-----BEGIN CERTIFICATE----- 
MIIDfTCCAuagAwIBAgIDErvmMA0GCSqGSIb3DQEBBQUAME4xCzAJBgNVBAYTAlVT 
....lots of base64... 
b8ravHNjkOR/ez4iyz0H7V84dJzjA1BOoa+Y7mHyhD8S 
-----END CERTIFICATE-----
--- 
Server certificate 
subject=/C=US/ST=California/L=Mountain View/O=Google Inc/CN=*.google.com 
issuer=/C=US/O=Google Inc/CN=Google Internet Authority G2 
---
No client certificate CA names sent 
Peer signing digest: SHA512 
Server Temp Key: ECDH, P-256, 256 bits

--- 
SSL handshake has read 4575 bytes and written 434 bytes 
--- 
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256 
Server public key is 2048 bit Secure Renegotiation IS supported 
Compression: NONE 
Expansion: NONE 
No ALPN negotiated 
SSL-Session:    
    Protocol : TLSv1.2 
    Cipher : ECDHE-RSA-AES128-GCM-SHA256 
    Session-ID: 48F046F3360225D51BE3362B50CE4FE8DB6D6B80B871C2A6DD5461850C4CF5AB 
    Session-ID-ctx: 
    Master-Key: 9A9CCBAA4F5A25B95C37EF7C6870F8C5DD3755A9A7B4CCE4535190B793DEFF53F94203AB0A62F9F70B9099FBFEBAB1B6 
    Key-Arg : None 
    PSK identity: None 
    PSK identity hint: None 
    SRP username: None 
    TLS session ticket lifetime hint: 100800 (seconds) 
    TLS session ticket: 
    0000 - 7a eb 54 dd ac 48 7e 76-30 73 b2 97 95 40 5b de z.T..H~v0s...@[. 
    0010 - f3 53 bf c8 41 36 66 3e-5b 35 a3 03 85 6f 7d 0c .S..A6f>[5...o}. 
    0020 - 4b a6 90 6f 95 e2 ec 03-31 5b 08 ca 65 6f 8f a6 K..o....1[..eo.. 
    0030 - 71 3d c1 53 b1 29 41 fc-d3 cb 03 bc a4 a9 33 28 q=.S.)A.......3( 
    0040 - f8 c8 6e 0a dc b3 e1 63-0e 8f f2 63 e6 64 0a 36 ..n....c...c.d.6 
    0050 - 22 cb 00 3a 59 1d 8d b2-5c 21 be 02 52 28 45 9d "..:Y...\!..R(E. 
    0060 - 72 e3 84 23 b6 f0 e2 7c-8a a3 e8 00 2b fd 42 1d r..#...|....+.B. 
    0070 - 23 35 6d f7 7d 85 39 1c-ad cd 49 f1 fd dd 15 de #5m.}.9...I..... 
    0080 - f6 9c ff 5e 45 9c 7c eb-6b 85 78 b5 49 ea c4 45 ...^E.|.k.x.I..E 
    0090 - 6e 02 24 1b 45 fc 41 a2-87 dd 17 4a 04 36 e6 63 n.$.E.A....J.6.c 
    00a0 - 72 a4 ad 
    00a4 - <SPACES/NULS> Start Time: 1476476711 Timeout : 300 (sec)
Verify return code: 0 (ok)
---

The first thing to note in this output is the last line, where you see the Verify return code. If there is a certificate issue, the return code will be non-zero and there will be a description of the error.

Expand this list of certificate error code to see common errors and how to remediate them

0 X509_V_OK The operation was successful.

2 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT The issuer certificate of an untrusted certificate could not be found.

3 X509_V_ERR_UNABLE_TO_GET_CRL The CRL of a certificate could not be found.

4 X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE The certificate signature could not be decrypted. This means that the actual signature value could not be determined rather than it not matching the expected value. This is only meaningful for RSA keys.

5 X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE The CRL signature could not be decrypted. This means that the actual signature value could not be determined rather than it not matching the expected value. Unused.

6 X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY The public key in the certificate SubjectPublicKeyInfo could not be read.

7 X509_V_ERR_CERT_SIGNATURE_FAILURE The signature of the certificate is invalid.

8 X509_V_ERR_CRL_SIGNATURE_FAILURE The signature of the certificate is invalid.

9 X509_V_ERR_CERT_NOT_YET_VALID The certificate is not yet valid: the notBefore date is after the current time. See Verify return code: 9 (certificate is not yet valid) below for more information.

10 X509_V_ERR_CERT_HAS_EXPIRED The certificate has expired; that is, the notAfter date is before the current time. See Verify return code: 10 (certificate has expired) below for more information.

11 X509_V_ERR_CRL_NOT_YET_VALID The CRL is not yet valid.

12 X509_V_ERR_CRL_HAS_EXPIRED The CRL has expired.

13 X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD The certificate notBefore field contains an invalid time.

14 X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD The certificate notAfter field contains an invalid time.

15 X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD The CRL lastUpdate field contains an invalid time.

16 X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD The CRL nextUpdate field contains an invalid time.

17 X509_V_ERR_OUT_OF_MEM An error occurred trying to allocate memory. This should never happen.

18 X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT The passed certificate is self-signed and the same certificate cannot be found in the list of trusted certificates.

19 X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN The certificate chain could be built up using the untrusted certificates but the root could not be found locally.

20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY The issuer certificate of a locally looked up certificate could not be found. This normally means the list of trusted certificates is not complete.

21 X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE No signatures could be verified because the chain contains only one certificate and it is not self-signed. See "Verify return code: 21 (unable to verify the first certificate)" below for more information. Verify return code: 21 (unable to verify the first certificate) below for more information.

22 X509_V_ERR_CERT_CHAIN_TOO_LONG The certificate chain length is greater than the supplied maximum depth. Unused.

23 X509_V_ERR_CERT_REVOKED The certificate has been revoked.

24 X509_V_ERR_INVALID_CA A CA certificate is invalid. Either it is not a CA or its extensions are not consistent with the supplied purpose.

25 X509_V_ERR_PATH_LENGTH_EXCEEDED The basicConstraints pathlength parameter has been exceeded.

26 X509_V_ERR_INVALID_PURPOSE The supplied certificate cannot be used for the specified purpose.

27 X509_V_ERR_CERT_UNTRUSTED The root CA is not marked as trusted for the specified purpose.

28 X509_V_ERR_CERT_REJECTED The root CA is marked to reject the specified purpose.

29 X509_V_ERR_SUBJECT_ISSUER_MISMATCH The current candidate issuer certificate was rejected because its subject name did not match the issuer name of the current certificate. Only displayed when the -issuer_checks option is set.

30 X509_V_ERR_AKID_SKID_MISMATCH The current candidate issuer certificate was rejected because its subject key identifier was present and did not match the authority key identifier current certificate. Only displayed when the -issuer_checks option is set.

31 X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH The current candidate issuer certificate was rejected because its issuer name and serial number were present and did not match the authority key identifier of the current certificate. Only displayed when the -issuer_checks option is set.

32 X509_V_ERR_KEYUSAGE_NO_CERTSIGN The current candidate issuer certificate was rejected because its keyUsage extension does not permit certificate signing.

50 X509_V_ERR_APPLICATION_VERIFICATION An application specific error. Unused.

New Certificate Detected

If you upgrade a device that has a self-signed certificate and a new certificate is generated after the upgrade process, CDO may generate a "New Certificate Detected" message as both a Configuration Status and Connectivity status. You must manually confirm and resolve this issue before you can continue managing it from CDO. Once the certificate is synchronized and the device is in a healthy state, you can manage the device.

Note	When you bulk reconnect more than one managed device to CDO at the same time, CDO automatically reviews and accepts the new certificates on the devices and continues to reconnect with them.

Use the following procedure to resolve a new certificate:

Navigate to the Inventory page.
Use the filter to display devices with a New Certificate Detected connectivity or configuration status and select the desired device.
In the action pane, click Review Certificate. CDO allows you to download the certificate for review and accept the new certificate.
In the Device Sync window, click Accept or in the Reconnecting to Device window, click Continue.

CDO automatically synchronizes the device with the new self-signed certificate. You may have to manually refresh the Inventory page to see the device once it's synched.

Certificate Error Codes

Verify return code: 0 (ok) but CDO returns certificate error

Once CDO has the certificate, it attempts to connect to the URL of the device by making a GET call to "https://<device_ip>:<port>". If this does not work, CDO will display a certificate error. If you find that the certificate is valid (openssl returns 0 ok) the problem may be that a different service is listening on the port you're trying to connect to. You can use the command:

 curl -k -u <username>:<password> https://<device_id>:<device_port>/admin/exec/show%20version

to determine whether you are definitely talking to an ASA and check if HTTPS server running on the correct port on the ASA:

 # show asp table socket
Protocol         Socket         State         Local Address             Foreign Address 
SSL             00019b98         LISTEN        192.168.1.5:443             0.0.0.0:* 
SSL             00029e18         LISTEN        192.168.2.5:443             0.0.0.0:* 
TCP             00032208         LISTEN        192.168.1.5:22              0.0.0.0:*

Verify return code: 9 (certificate is not yet valid)

This error means that the issuance date of the certificate provided is in the future, so clients will not treat it as valid. This can be caused by a poorly-constructed certificate, or in the case of a self-signed certificate it can be cause by the device time being wrong when it generated the certificate.

You should see a line in the error including the notBefore date of the certificate:

depth=0 CN = ASA Temporary Self Signed Certificate 
verify error:num=18:self signed certificate 
verify return:1 
depth=0 CN = ASA Temporary Self Signed Certificate 
verify error:num=9:certificate is not yet valid
notBefore=Oct 21 19:43:15 2016 GMT 
verify return:1 
depth=0 CN = ASA Temporary Self Signed Certificate 
notBefore=Oct 21 19:43:15 2016 GMT

From this error, you can determine when the certificate will become valid.

Remediation

The notBefore date of the certificate needs to be in the past. You can reissue the certificate with an earlier notBefore date. This issue can also arise when the time is not set correctly either on the client or issuing device.

Verify return code: 10 (certificate has expired)

This error means that at least one of the certificates provided has expired. You should see a line in the error including the notBefore date of the certificate:

 error 10 at 0 depth lookup:certificate has expired

The expiration date is located in the certificate body.

Remediation

If the certificate is truly expired, the only remediation is to get another certificate. If the certificate's expiration is still in the future, but openssl claims that it is expired, check the time and date on your computer. For instance, if a certificate is set to expire in the year 2020, but the date on your computer is in 2021, your computer will treat that certificate as expired.

Verify return code: 21 (unable to verify the first certificate)

This error indicates that there is a problem with the certificate chain, and openssl cannot verify that the certificate presented by the device should be trusted. Let's look at the certificate chain from the example above to see how certificate chains should work:

--- 
Certificate chain 
0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=*.google.com 
i:/C=US/O=Google Inc/CN=Google Internet Authority G2

-----BEGIN CERTIFICATE----- 
MIIH0DCCBrigAwIBAgIIUOMfH+8ftN8wDQYJKoZIhvcNAQELBQAwSTELMAkGA1UE 
....lots of base64... 
tzw9TylimhJpZcl4qihFVTgFM7rMU2VHulpJgA59gdbaO/Bf 
-----END CERTIFICATE----- 

1 s:/C=US/O=Google Inc/CN=Google Internet Authority G2 
i:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA 

-----BEGIN CERTIFICATE----- 
MIID8DCCAtigAwIBAgIDAjqSMA0GCSqGSIb3DQEBCwUAMEIxCzAJBgNVBAYTAlVT 
....lots of base64... 
tzw9TylimhJpZcl4qihFVTgFM7rMU2VHulpJgA59gdbaO/Bf 
-----END CERTIFICATE----- 

2 s:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA 
i:/C=US/O=Equifax/OU=Equifax Secure Certificate Authority 

-----BEGIN CERTIFICATE----- 
MIIDfTCCAuagAwIBAgIDErvmMA0GCSqGSIb3DQEBBQUAME4xCzAJBgNVBAYTAlVT 
....lots of base64... 
b8ravHNjkOR/ez4iyz0H7V84dJzjA1BOoa+Y7mHyhD8S 
-----END CERTIFICATE----- ---

The certificate chain is a list of certificates presented by the server, beginning with the server's own certificate and then including increasingly higher-level intermediate certificates linking the server's certificate with a Certificate Authority's top-level certificate. Each certificate lists its Subject (the line starting with 's:' and its Issuer (the line starting with 'i').

The Subject is the entity identified by the certificate. It includes the Organization name and sometimes the Common Name of the entity for which the certificate was issued.

The Issuer is the entity that issued the certificate. It also includes an Organization field and sometimes a Common Name.

If a server had a certificate issued directly by a trusted Certificate Authority, it would not need to include any other certificates in its certificate chain. It would present one certificate that looked like:

--- Certificate chain 0 s:/C=US/ST=California/L=Anytown/O=ExampleCo/CN=*.example.com i:/C=US/O=Trusted Authority/CN=Trusted Authority 
-----BEGIN CERTIFICATE----- 
MIIH0DCCBrigAwIBAgIIUOMfH+8ftN8wDQYJKoZIhvcNAQELBQAwSTELMAkGA1UE 
....lots of base64... 
tzw9TylimhJpZcl4qihFVTgFM7rMU2VHulpJgA59gdbaO/Bf 
-----END CERTIFICATE----- ---

Given this certificate, openssl would verify that the ExampleCo certificate for *.example.com was correctly signed by the Trusted Authority certificate, which would be present in openssl's built-in trust store. After that verification, openssl would successfully connect to the device.

However, most servers do not have certificates signed directly by a trusted CA. Instead, as in the first example, the server's certificate is signed by one or more intermediates, and the highest-level intermediate has a certificate signed by the trusted CA. OpenSSL does not trust these intermediate CAs by default, and can only verify them if it is given a complete certificate chain ending in a trusted CA.

It is critically important that servers whose certificates are signed by intermediate authorities supply ALL the certificates linking them to a trusted CA, including all of the intermediate certificates. If they don't supply this entire chain, the output from openssl will look something like this:

depth=0 OU = Example Unit, CN = example.com 
verify error:num=20:unable to get local issuer certificate 
verify return:1 

depth=0 OU = Example Unit, CN = example.com 
verify error:num=27:certificate not trusted 
verify return:1 

depth=0 OU = Example Unit, CN = example.com 
verify error:num=21:unable to verify the first certificate 
verify return:1

CONNECTED(00000003)

--- 
Certificate chain 
0 s:/OU=Example Unit/CN=example.com 
i:/C=US/ST=Massachusetts/L=Cambridge/O=Intermediate Authority/OU=http://certificates.intermediateauth...N=Intermediate Certification Authority/sn=675637734 
-----BEGIN CERTIFICATE-----
...lots of b64...
-----END CERTIFICATE-----
--- 
Server certificate 
subject=/OU=Example Unit/CN=example.com 
issuer=/C=US/ST=Massachusetts/L=Cambridge/O=Intermediate Authority/OU=http://certificates.intermediateauth...N=Intermediate Certification Authority/sn=675637734 
--- 
No client certificate CA names sent 
--- 
SSL handshake has read 1509 bytes and written 573 bytes
---
New, TLSv1/SSLv3, Cipher is AES256-SHA 
Server public key is 2048 bit 
Secure Renegotiation IS NOT supported 
Compression: NONE 
Expansion: NONE 
SSL-Session: 
Protocol : TLSv1 
Cipher : AES256-SHA 
Session-ID: 24B45B2D5492A6C5D2D5AC470E42896F9D2DDDD54EF6E3363B7FDA28AB32414B 
Session-ID-ctx: 
Master-Key: 21BAF9D2E1525A5B935BF107DA3CAF691C1E499286CBEA987F64AE5F603AAF8E65999BD21B06B116FE9968FB7C62EF7C 
Key-Arg : None 
Krb5 Principal: None 
PSK identity: None 
PSK identity hint: None 
Start Time: 1476711760 
Timeout : 300 (sec) 
Verify return code: 21 (unable to verify the first certificate) 
---

This output shows that the server only provided one certificate, and the provided certificate was signed by an intermediate authority, not a trusted root. The output also shows the characteristic verification errors.

Remediation

This problem is caused by a misconfigured certificate presented by the device. The only way to fix this so that CDO or any other program can securely connect to the device is to load the correct certificate chain onto the device, so that it will present a complete certificate chain to connecting clients.

To include the intermediate CA to the trustpoint follow one of the links below (depending on your case - if CSR was generated on the ASA or not):