IdentityServer4, WindowsCryptographicException: The system cannot find the file specified - asp.net-core

Question

I create an IdentityServer4 project with several client apps. I use a self-signed certificate file my_certificate.pfx to generate login token. It works fine on localhost.
However, it does not work when employing it to a shared web hosting server.
The app that hosts the IdentityServer4 works fine, indicating that the server app can access the certificate file. However, it generates the following error when trying to log in from a client app:
WindowsCryptographicException: The system cannot find the file specified.
System.Security.Cryptography.CngKey.Open(string keyName, CngProvider provider, CngKeyOpenOptions openOptions)
System.Security.Cryptography.CngKey.Open(string keyName, CngProvider provider)
Internal.Cryptography.Pal.CertificatePal.GetPrivateKey<T>(Func<CspParameters, T> createCsp, Func<CngKey, T> createCng)
Internal.Cryptography.Pal.CertificatePal.GetRSAPrivateKey()
System.Security.Cryptography.X509Certificates.X509Certificate2.get_PrivateKey()
Microsoft.IdentityModel.Tokens.X509SecurityKey.get_PrivateKey()
Microsoft.IdentityModel.Tokens.X509SecurityKey.get_PrivateKeyStatus()
Microsoft.IdentityModel.Tokens.AsymmetricSignatureProvider.FoundPrivateKey(SecurityKey key)
Microsoft.IdentityModel.Tokens.AsymmetricSignatureProvider..ctor(SecurityKey key, string algorithm, bool willCreateSignatures)
Microsoft.IdentityModel.Tokens.AsymmetricSignatureProvider..ctor(SecurityKey key, string algorithm, bool willCreateSignatures, CryptoProviderFactory cryptoProviderFactory)
Microsoft.IdentityModel.Tokens.CryptoProviderFactory.CreateSignatureProvider(SecurityKey key, string algorithm, bool willCreateSignatures)
Microsoft.IdentityModel.Tokens.CryptoProviderFactory.CreateForSigning(SecurityKey key, string algorithm)
Microsoft.IdentityModel.JsonWebTokens.JwtTokenUtilities.CreateEncodedSignature(string input, SigningCredentials signingCredentials)
System.IdentityModel.Tokens.Jwt.JwtSecurityTokenHandler.WriteToken(SecurityToken token)
IdentityServer4.Services.DefaultTokenCreationService.CreateJwtAsync(JwtSecurityToken jwt)
IdentityServer4.Services.DefaultTokenCreationService.CreateTokenAsync(Token token)
IdentityServer4.Services.DefaultTokenService.CreateSecurityTokenAsync(Token token)
IdentityServer4.ResponseHandling.AuthorizeResponseGenerator.CreateImplicitFlowResponseAsync(ValidatedAuthorizeRequest request, string authorizationCode)
IdentityServer4.ResponseHandling.AuthorizeResponseGenerator.CreateHybridFlowResponseAsync(ValidatedAuthorizeRequest request)
IdentityServer4.ResponseHandling.AuthorizeResponseGenerator.CreateResponseAsync(ValidatedAuthorizeRequest request)
IdentityServer4.Endpoints.AuthorizeEndpointBase.ProcessAuthorizeRequestAsync(NameValueCollection parameters, ClaimsPrincipal user, ConsentResponse consent)
IdentityServer4.Endpoints.AuthorizeEndpoint.ProcessAsync(HttpContext context)
IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events)
IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events)
IdentityServer4.Hosting.MutualTlsTokenEndpointMiddleware.Invoke(HttpContext context, IAuthenticationSchemeProvider schemes)
Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
IdentityServer4.Hosting.BaseUrlMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
NWebsec.AspNetCore.Middleware.Middleware.MiddlewareBase.Invoke(HttpContext context)
NWebsec.AspNetCore.Middleware.Middleware.MiddlewareBase.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
How to make the client app works?
Thanks

Answer 1

I ran into this when setting up IdentityServer on AWS ElasticBeanstalk infrastructure and using a local file, rather than the certificate store - however the solution in my case is the same. I found that the app pools on the EC2 instances did not have Load User Profile set true. When set, the permissions model changes and allows the process to load in the cert. You can enable through the IIS management UI on the app pool details, or use a version of the script below.
Import-Module WebAdministration
Set-ItemProperty "IIS:\AppPools\DefaultAppPool" -Name "processModel.loadUserProfile" -Value "True"