Have a number of computers where user certificates suddenly stop working.
certutil -silent -user -store my shows that all user certificates for the affected user have stopped working.
my ================ Certificate 0 ================ Serial Number: 2a0000210be8f0775a3a2e2b7200040000210b Issuer: CN=PROD Issuing CA, DC=somecompany, DC=Com, DC=Au NotBefore: 10/01/2017 7:46 AM NotAfter: 10/01/2018 7:46 AM Subject: CN=username, OU=somecompany, OU=Level 1, OU=Laptop Users, OU=Special Group Users, DC=somecompany, DC=Com, DC=Au Non-root Certificate Template: 220.127.116.11.4.1.318.104.22.16886432.4805332.10505398.7351119.9274134.0.14270575.7769536 Cert Hash(sha1): cc 3b d0 2c 03 a1 d9 d4 0d 28 31 a7 84 c8 6d cb 6d 97 27 d8 Key Container = 48fa6c038e897eb98ea252b465308c55_7cc43284-5d87-4ba0-8673-6fb4d4de8f2d Provider = Microsoft Enhanced Cryptographic Provider v1.0 Cannot find the certificate and private key for decryption. ================ Certificate 1 ================ Serial Number: 7b4d6131959b5f6cd272 Issuer: CN=Communications Server NotBefore: 25/08/2017 10:41 AM NotAfter: 25/08/2017 6:41 PM Subject: CNfirstname.lastname@example.org Non-root Certificate Template: Cert Hash(sha1): 80 25 75 64 60 77 21 16 35 18 ee 04 4f 87 bc 5f f0 ae b3 2a Key Container = OC_KeyContainer_Lync_someguy@somecompany.com.au Provider = Microsoft Enhanced Cryptographic Provider v1.0 Cannot find the certificate and private key for decryption.
%APPDATA%\Microsoft\Crypto\RSA folder can see the private key files are present i.e. in this case of first certificate
What are potential causes for this issue ? I suspect the encryption key for the private key is being erased/modified; but wonder how to confirm if this is being changed.
In this case we use the Cert Hash(sha1) to find the user’s certificate in
%APPDATA%\Microsoft\SystemCertificates\My\Certificates\CC3BD02C03A1D9D40D2831A784C86DCB6D9727D8 which is present.
Then using key container field we find the private key in
%APPDATA%\Microsoft\Crypto\RSA\S-1-5-21-2091123715-180627453-533688462-45495\48fa6c038e897eb98ea252b465308c55_7cc43284-5d87-4ba0-8673-6fb4d4de8f2d which is also present.
The files were modified:
• SystemCertificates file CC3BD02C03A1D9D40D2831A784C86DCB6D9727D8 was last modified 25/08/2017 10:55am. Was this when a new key was requested i.e. had user reported problem before this time?
• Private key file under
%APPDATA%\Microsoft\Crypto\RSA\S-1-5-21-2091123715-180627453-533688462-45495\48fa6c038e897eb98ea252b465308c55_7cc43284-5d87-4ba0-8673-6fb4d4de8f2d was last modified 10/01/2017 7:56 am (Close to time issued on system certificate file)
• The private key was encrypted with master key stored in
%APPDATA%\Microsoft\Protect\<user SID>\c77f3872-e1e2-4449-9729-cc97e85e4a3c which was last modified 25/07/2017 8:19 am
• The Protect folder containing master key used to decrypt private keys, has files last modified on 14/08/2017 8:23am
%APPDATA%\Microsoft\SystemCertificates\My\Certificates has 0 byte certificate files modified 12/07/2017 12:00am – 7:50 am at different intervals and 8/06/2017 11:52 pm – 9/06/2017 8:33 am every 8 minutes
Currently we are using Windows auditing to look for modifications to
%APPDATA%\Microsoft\SystemCertificates folder and
However given that the certificate and private key files seem to exist, not sure if this will identify cause.
The application log also has errors for CertificateServicesClient-AutoEnrollment source:
Automatic certificate enrollment for domain\username failed (0x8007003a) The specified server cannot perform the requested operation.
Any recommended steps for further identifying root cause of "Cannot find the certificate and private key for decryption." error?