Windows authentication in linux docker container - kerberos

Question

i am trying to use windows authentication in linux docker container under kubernetes.
I am following this settings: https://learn.microsoft.com/en-us/aspnet/core/security/authentication/windowsauth?view=aspnetcore-3.1&tabs=visual-studio#kestrel
App is in .net core3, with nuget Microsoft.AspNetCore.Authentication.Negotiate and running in kestrel
I have added the
services.AddAuthentication(Microsoft.AspNetCore.Authentication.Negotiate.NegotiateDefaults.AuthenticationScheme).AddNegotiate();
as well as
app.UseAuthentication();
and setup my devbase image as
FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster as final
USER root
RUN whoami
RUN apt update && apt dist-upgrade -y
ADD ca/ca.crt /usr/local/share/ca-certificates/ca.crt
RUN chmod 644 /usr/local/share/ca-certificates/*
RUN update-ca-certificates
RUN DEBIAN_FRONTEND=noninteractive apt install -y krb5-config krb5-user
COPY krb5.conf /etc/krb5.conf
RUN mkdir /app
RUN echo BQIAAA..== | base64 -d > /app/is.k01.HTTP.keytab
WORKDIR /app
#RUN docker version
RUN groupadd --gid 1000 app && useradd --uid 1000 --gid app --shell /bin/bash -d /app app
RUN apt install -y mc sudo syslog-ng realmd gss-ntlmssp
the build in tfs pipeline creates app docker image derived from above and adds following env variables, also copies build to /app
RUN chmod 0700 run.sh
ENV KRB5_KTNAME=/app/is.k01.HTTP.keytab
ENV KRB5_TRACE=/dev/stdout
ENV ASPNETCORE_URLS=http://*:80;https://+:443
RUN chown app:app /app -R
USER app
the app is being run by run.sh
service syslog-ng start
kinit HTTP/is.k01.mydomain.com#MYDOMAIN.COM -k -t /app/is.k01.HTTP.keytab
klist
dotnet dev-certs https
dotnet /app/SampleApi.dll
klist lists the principal which has assigned the SPN to the machine
in ie and firefox i have added the network.negotiate-auth.trusted-uris to my app
however i am getting the login dialog with no success to log in
so the question is:
How can I enable debug log with Microsoft.AspNetCore.Authentication.Negotiate package?
My assumption is that this package does not communicate with kerberos properly, perhaps some package is missing, not running or something.
Also note that the container and .net app is connected successfully to the domain because I use integrated security for connection to the database which works.
**** Edit > Answer to first part
To enable logs, one should enable logs in kestrel:
in appsettings.json:
"Logging": {
"LogLevel": {
"Default": "Debug",
}
},
In program.cs:
Host.CreateDefaultBuilder(args)
.ConfigureLogging(logging =>
{
logging.AddFilter("Microsoft", LogLevel.Debug);
logging.AddFilter("System", LogLevel.Debug);
logging.ClearProviders();
logging.AddConsole();
})
.ConfigureWebHostDefaults(webBuilder =>
{
In Startup.cs one can track the negotiate events:
services.AddAuthentication(NegotiateDefaults.AuthenticationScheme).AddNegotiate(
options =>
{
options.PersistKerberosCredentials = true;
options.Events = new NegotiateEvents()
{
OnAuthenticated = challange =>
{
..
},
OnChallenge = challange =>
{
..
},
OnAuthenticationFailed = context =>
{
// context.SkipHandler();
Console.WriteLine($"{DateTimeOffset.Now.ToString(czechCulture)} OnAuthenticationFailed/Scheme: {context.Scheme.Str()}, Request: {context.Request.Str()}");
Console.WriteLine("context?.HttpContext?.Features?.Select(f=>f.Key.Name.ToString())");
var items = context?.HttpContext?.Features?.Select(f => "- " + f.Key?.Name?.ToString());
if (items != null)
{
Console.WriteLine(string.Join("\n", items));
}
Console.WriteLine("context.HttpContext.Features.Get<IConnectionItemsFeature>()?.Items " + context.HttpContext.Features.Get<IConnectionItemsFeature>()?.Items?.Count);
var items2 = context.HttpContext?.Features.Get<IConnectionItemsFeature>()?.Items?.Select(f => "- " + f.Key?.ToString() + "=" + f.Value?.ToString());
if (items2 != null) {
Console.WriteLine(string.Join("\n", items2));
}
return Task.CompletedTask;
}
};
}
);
**** Edit
Meanwhile according my goal to allow windows authentication in .net core docker web app i was going through the source code of .net core, and corefx and trucated the auth code to this sample console app:
try
{
var token = "MyToken==";
var secAssembly = typeof(AuthenticationException).Assembly;
Console.WriteLine("var ntAuthType = secAssembly.GetType(System.Net.NTAuthentication, throwOnError: true);");
var ntAuthType = secAssembly.GetType("System.Net.NTAuthentication", throwOnError: true);
Console.WriteLine("var _constructor = ntAuthType.GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance).First();");
var _constructor = ntAuthType.GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance).First();
Console.WriteLine("var credential = CredentialCache.DefaultCredentials;");
var credential = CredentialCache.DefaultCredentials;
Console.WriteLine("var _instance = _constructor.Invoke(new object[] { true, Negotiate, credential, null, 0, null });");
var _instance = _constructor.Invoke(new object[] { true, "Negotiate", credential, null, 0, null });
var negoStreamPalType = secAssembly.GetType("System.Net.Security.NegotiateStreamPal", throwOnError: true);
var _getException = negoStreamPalType.GetMethods(BindingFlags.NonPublic | BindingFlags.Static).Where(info => info.Name.Equals("CreateExceptionFromError")).Single();
Console.WriteLine("var _getOutgoingBlob = ntAuthType.GetMethods(BindingFlags.NonPublic | BindingFlags.Instance).Where(info => info.Name.Equals(GetOutgoingBlob) && info.GetParameters().Count() == 3).Single();");
var _getOutgoingBlob = ntAuthType.GetMethods(BindingFlags.NonPublic | BindingFlags.Instance).Where(info => info.Name.Equals("GetOutgoingBlob") && info.GetParameters().Count() == 3).Single();
Console.WriteLine("var decodedIncomingBlob = Convert.FromBase64String(token);;");
var decodedIncomingBlob = Convert.FromBase64String(token);
Console.WriteLine("var parameters = new object[] { decodedIncomingBlob, false, null };");
var parameters = new object[] { decodedIncomingBlob, false, null };
Console.WriteLine("var blob = (byte[])_getOutgoingBlob.Invoke(_instance, parameters);");
var blob = (byte[])_getOutgoingBlob.Invoke(_instance, parameters);
if (blob != null)
{
Console.WriteLine("var out1 = Convert.ToBase64String(blob);");
var out1 = Convert.ToBase64String(blob);
Console.WriteLine(out1);
}
else
{
Console.WriteLine("null blob value returned");
var securityStatusType = secAssembly.GetType("System.Net.SecurityStatusPal", throwOnError: true);
var _statusException = securityStatusType.GetField("Exception");
var securityStatus = parameters[2];
var error = (Exception)(_statusException.GetValue(securityStatus) ?? _getException.Invoke(null, new[] { securityStatus }));
Console.WriteLine("Error:");
Console.WriteLine(error);
Console.WriteLine("securityStatus:");
Console.WriteLine(securityStatus.ToString());
}
}
catch(Exception exc)
{
Console.WriteLine(exc.Message);
}
So i found out that the library communicates with
System.Net.NTAuthentication
which communicates with
System.Net.Security.NegotiateStreamPal
which communicates with unix version of
Interop.NetSecurityNative.InitSecContext
which should somehow trigger the GSSAPI in os
In dotnet runtime git they tell us that gss-ntlmssp is required for this to work even that it is not mentioned anyhow in the aspnet core documentation.
https://github.com/dotnet/runtime/issues?utf8=%E2%9C%93&q=gss-ntlmssp
Nevertheless I have compiled the gss-ntlmssp and found out that without this library it throws error "An unsupported mechanism was requested.". With my library it throws error "No credentials were supplied, or the credentials were unavailable or inaccessible.", but never access to any gss_* methods.
I have tested usage of gss methods by adding the log entry to file which never occured.. fe:
OM_uint32 gss_init_sec_context(OM_uint32 *minor_status,
gss_cred_id_t claimant_cred_handle,
gss_ctx_id_t *context_handle,
gss_name_t target_name,
gss_OID mech_type,
OM_uint32 req_flags,
OM_uint32 time_req,
gss_channel_bindings_t input_chan_bindings,
gss_buffer_t input_token,
gss_OID *actual_mech_type,
gss_buffer_t output_token,
OM_uint32 *ret_flags,
OM_uint32 *time_rec)
{
FILE *fp;
fp = fopen("/tmp/gss-debug.log", "w+");
fprintf(fp, "gss_init_sec_context\n");
fclose(fp);
return gssntlm_init_sec_context(minor_status,
claimant_cred_handle,
context_handle,
target_name,
mech_type,
req_flags,
time_req,
input_chan_bindings,
input_token,
actual_mech_type,
output_token,
ret_flags,
time_rec);
}
So .net calls gssapi, and gssapi does not call mechanism.
I have observed the same behavior in centos7 vm, ubuntu windows subsystem, and debian docker image (customized mcr.microsoft.com/dotnet/core/sdk:3.1-buster)
So the question now is, how can I debug gssapi ?
I assume my current gssapi is managed by this library:
readelf -d /usr/lib64/libgssapi_krb5.so
Dynamic section at offset 0x4aa48 contains 34 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libkrb5.so.3]
0x0000000000000001 (NEEDED) Shared library: [libk5crypto.so.3]
0x0000000000000001 (NEEDED) Shared library: [libcom_err.so.2]
0x0000000000000001 (NEEDED) Shared library: [libkrb5support.so.0]
0x0000000000000001 (NEEDED) Shared library: [libdl.so.2]
0x0000000000000001 (NEEDED) Shared library: [libkeyutils.so.1]
0x0000000000000001 (NEEDED) Shared library: [libresolv.so.2]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000e (SONAME) Library soname: [libgssapi_krb5.so.2]
0x000000000000000c (INIT) 0xb1d8
0x000000000000000d (FINI) 0x3ebcc
0x0000000000000019 (INIT_ARRAY) 0x24a120
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x24a128
0x000000000000001c (FINI_ARRAYSZ) 16 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x1f0
0x0000000000000005 (STRTAB) 0x3048
0x0000000000000006 (SYMTAB) 0x720
0x000000000000000a (STRSZ) 9167 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000003 (PLTGOT) 0x24b000
0x0000000000000002 (PLTRELSZ) 8088 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x9240
0x0000000000000007 (RELA) 0x58b0
0x0000000000000008 (RELASZ) 14736 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffc (VERDEF) 0x5788
0x000000006ffffffd (VERDEFNUM) 3
0x000000006ffffffe (VERNEED) 0x57e0
0x000000006fffffff (VERNEEDNUM) 4
0x000000006ffffff0 (VERSYM) 0x5418
0x000000006ffffff9 (RELACOUNT) 504
0x0000000000000000 (NULL) 0x0
so far i have compiled new latest gssapi from mit source, and found out that it is throwing me error "An unsupported mechanism was requested." because gssapi requires gss interpreter which is not provided. In centos7 i had another issue that the openssl library was using shared kerberos library which was incompatible, thus yum stopped working.
*** edit
I have found out that the gss-ntlmssp has flag GSS_C_MA_NOT_DFLT_MECH thus it was failing with the message "No credentials were supplied, or the credentials were unavailable or inaccessible.". The solution is to build custom gss-ntlmssp without this attribute because i desire to use it as default auth mechanism.
My sample console app to check credentials works now, I will try to put it work in docker container now.
*** edit
I was able to run my ConsoleApp successfully in kubernetes:
FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster as final
USER root
RUN whoami
RUN apt update && apt dist-upgrade -y
ADD ca/ca.crt /usr/local/share/ca-certificates/ca.crt
RUN chmod 644 /usr/local/share/ca-certificates/*
RUN update-ca-certificates
RUN DEBIAN_FRONTEND=noninteractive apt install -y krb5-config krb5-user
RUN mkdir /app
RUN apt install -y mc sudo syslog-ng python3-software-properties software-properties-common packagekit git gssproxy vim
RUN apt install -y autoconf automake libxslt-dev doxygen findutils libgettextpo-dev libtool m4 make libunistring-dev libssl-dev zlib1g-dev gettext xsltproc libxml2-utils libxml2-dev xml-core docbook-xml docbook-xsl bison libkrb5-dev
RUN systemctl enable syslog-ng
RUN mkdir /src
RUN cd /src && wget https://web.mit.edu/kerberos/dist/krb5/1.18/krb5-1.18.tar.gz
RUN cd /src && tar -xf krb5-1.18.tar.gz
RUN cd /src/krb5-1.18/src && ./configure && make && make install
RUN cd /src && git clone https://github.com/scholtz/gss-ntlmssp.git
RUN cd /src/gss-ntlmssp/ && autoreconf -f -i && ./configure && make && make install
RUN cp /src/gss-ntlmssp/examples/mech.ntlmssp.conf /etc/gss/mech.d/mech.ntlmssp.conf
COPY testgss /testgss
RUN cd /testgss && dotnet ConsoleApp3.dll
RUN groupadd --gid 1000 app && useradd --uid 1000 --gid app --shell /bin/bash -d /app app
RUN echo BQIA..AAAB | base64 -d > /app/user.keytab
RUN echo BQIA..oQ== | base64 -d > /etc/krb5.keytab
RUN echo BQIA..oQ== | base64 -d > /app/is.k01.HTTP.keytab
RUN echo BQIA..AAA= | base64 -d > /app/is.k01.kerb.keytab
COPY krb5.conf /etc/krb5.conf
COPY krb5.conf /usr/local/etc/krb5.conf
RUN ln -s /etc/gss /usr/local/etc/gss
RUN cd /app
WORKDIR /app
However, i am getting this error now:
System.Exception: An authentication exception occured (0xD0000/0x4E540016).
---> Interop+NetSecurityNative+GssApiException: GSSAPI operation failed with error - Unspecified GSS failure. Minor code may provide more information (Feature not available).
at System.Net.Security.NegotiateStreamPal.GssAcceptSecurityContext(SafeGssContextHandle& context, Byte[] buffer, Byte[]& outputBuffer, UInt32& outFlags)
at System.Net.Security.NegotiateStreamPal.AcceptSecurityContext(SafeFreeCredentials credentialsHandle, SafeDeleteContext& securityContext, ContextFlagsPal requestedContextFlags, Byte[] incomingBlob, ChannelBinding channelBinding, Byte[]& resultBlob, ContextFlagsPal& contextFlags)
*** edit
Now it fails in here:
gssntlm_init_sec_context..
gssntlm_acquire_cred..
gssntlm_acquire_cred_from..
if (cred_store != GSS_C_NO_CRED_STORE) {
retmin = get_creds_from_store(name, cred, cred_store);
} else {
retmin = get_user_file_creds(name, cred);
if (retmin) {
retmin = external_get_creds(name, cred);
}
}
get_user_file_creds() returns error as i do not have specific file setup as i want to verify users from ad
external_get_creds() fails here:
wbc_status = wbcCredentialCache(&params, &result, NULL);
if(!WBC_ERROR_IS_OK(wbc_status)) goto done;
external_get_creds tries to authenticate with winbind library and obviously in the credential cache there is no user present
i managed to compile it with the winbind library that samba has provided
so the question now is:
How to setup winbind library to communicate with AD?
*** Edit
I have tried to use .net 5 as at github i was told that NTLM works in .net 5. However i get the same result as with .net 3.1.
Docker image with which i have tried that:
FROM mcr.microsoft.com/dotnet/core-nightly/sdk:5.0-buster as final
USER root
RUN whoami
RUN apt update && apt dist-upgrade -y
RUN DEBIAN_FRONTEND=noninteractive apt install -y krb5-config krb5-user
RUN mkdir /app
RUN apt install -y mc sudo syslog-ng python3-software-properties software-properties-common packagekit git gssproxy vim apt-utils
RUN apt install -y autoconf automake libxslt-dev doxygen findutils libgettextpo-dev libtool m4 make libunistring-dev libssl-dev zlib1g-dev gettext xsltproc libxml2-utils libxml2-dev xml-core docbook-xml docbook-xsl bison libkrb5-dev
RUN systemctl enable syslog-ng
RUN mkdir /src
#RUN cd /src && git clone https://github.com/scholtz/gss-ntlmssp.git
RUN DEBIAN_FRONTEND=noninteractive apt install -y libwbclient-dev samba samba-dev
#RUN cat /usr/include/samba-4.0/wbclient.h
COPY gss-ntlmssp /usr/local/src/gss-ntlmssp
RUN cd /usr/local/src/gss-ntlmssp/ && autoreconf -f -i && ./configure && make && make install
RUN cp /usr/local/src/gss-ntlmssp/examples/mech.ntlmssp.conf /etc/gss/mech.d/mech.ntlmssp.conf
RUN groupadd --gid 1000 app && useradd --uid 1000 --gid app --shell /bin/bash -d /app app
RUN echo BQIAAABMA..ArHdoQ== | base64 -d > /etc/krb5.keytab
COPY krb5.conf /etc/krb5.conf
COPY smb.conf /etc/samba/smb.conf
COPY krb5.conf /usr/local/etc/krb5.conf
RUN DEBIAN_FRONTEND=noninteractive apt install -y winbind
ENV KRB5_TRACE=/dev/stdout
RUN mkdir /src2
WORKDIR /src2
RUN dotnet --list-runtimes
RUN dotnet new webapi --auth Windows
RUN dotnet add package Microsoft.AspNetCore.Authentication.Negotiate
RUN sed -i '/services.AddControllers/i services.AddAuthentication(Microsoft.AspNetCore.Authentication.Negotiate.NegotiateDefaults.AuthenticationScheme).AddNegotiate();' Startup.cs
RUN sed -i '/app.UseAuthorization/i app.UseAuthentication();' Startup.cs
run echo a
RUN cat Startup.cs
RUN dotnet restore
RUN dotnet build
ENV ASPNETCORE_URLS="http://*:5002;https://*:5003"
EXPOSE 5002
EXPOSE 5003
RUN cd /app
WORKDIR /app
docker run -it -p 5003:5003 -it registry.k01.mydomain.com/k01-devbase:latest
In docker container:
kinit HTTP/myuser#MYDOMAIN.COM -k -t /etc/krb5.keytab
klist
dotnet run src2.dll
I have put my own debug info in gssntlmssp library and i put it to file
cat /tmp/gss-debug.log
This is exactly the same end where i finished with .net core 3.1 .
wbcCredentialCache (samba lib) fails at the point where it cannot find cached credentials
This is my krb5.conf:
[appdefaults]
default_lifetime = 25hrs
krb4_convert = false
krb4_convert_524 = false
ksu = {
forwardable = false
}
pam = {
minimum_uid = 100
forwardable = true
}
pam-afs-session = {
minimum_uid = 100
}
[libdefaults]
default_realm = MYDOMAIN.COM
[realms]
MYDOMAIN.COM = {
kdc = DC01.MYDOMAIN.COM
default_domain = MYDOMAIN.COM
}
[domain_realm]
mydomain.com. = MYDOMAIN.COM
.mydomain.com. = MYDOMAIN.COM
[logging]
default = CONSOLE
default = SYSLOG:INFO
default = FILE:/var/log/krb5-default.log
kdc = CONSOLE
kdc = SYSLOG:INFO:DAEMON
kdc = FILE:/var/log/krb5-kdc.log
admin_server = SYSLOG:INFO
admin_server = DEVICE=/dev/tty04
admin_server = FILE:/var/log/krb5-kadmin.log
and part of samba file:
[global]
security = domain
workgroup = mydomain.com
password server = *
idmap config * : range = 16777216-33554431
template shell = /bin/bash
winbind use default domain = yes
winbind offline logon = false
wins server = 10.0.0.2
In my opinion i would like more to have NTLM then Negotiate because Negotiate is not supported among browsers as far as I know. For example in firefox the person must setup the about:config for negotiate server. Wildcards are not supported, ...
nevertheless it seems that i will not be able to run .net core 5 web app with ntlm, so i will attempt to setup it without the gssntlmssp library now with some default kerberos mechanism. Any idea what is wrong with my krb5.conf settings?
**** Edit
So I am now trying two different approaches:
NTLM - in my opinion this is preferable way as i have seen ntlm authenticate users in iis express for example without the dialog box, and does not require any special configuration in firefox or through group policy (please fix me if I am wrong)
Negotiate
With regards for the negotiate i have managed to make some progres..
With this docker container i was able to get around the unsupported mechanism:
FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster as final
USER root
RUN whoami
RUN apt update && apt dist-upgrade -y
RUN DEBIAN_FRONTEND=noninteractive apt install -y krb5-config krb5-user
RUN mkdir /app
RUN apt install -y mc sudo syslog-ng python3-software-properties software-properties-common packagekit git gssproxy vim apt-utils
RUN apt install -y autoconf automake libxslt-dev doxygen findutils libgettextpo-dev libtool m4 make libunistring-dev libssl-dev zlib1g-dev gettext xsltproc libxml2-utils libxml2-dev xml-core docbook-xml docbook-xsl bison libkrb5-dev
RUN systemctl enable syslog-ng
RUN mkdir /src
RUN groupadd --gid 1000 app && useradd --uid 1000 --gid app --shell /bin/bash -d /app app
RUN echo BQIAAAA8..vI | base64 -d > /etc/krb5.keytab
COPY krb5.conf /etc/krb5.conf
COPY krb5.conf /usr/local/etc/krb5.conf
ADD ca/is.k01.mydomain.com.p12 /etc/ssl/certs/is.k01.mydomain.com.pfx
RUN cd /app
WORKDIR /app
However now I have other issue:
Request ticket server HTTP/is.k01.mydomain.com#MYDOMAIN.com kvno 3 found in keytab but not with enctype rc4-hmac
This seems to me that the keytab is not with rc4-hmac which is true, because the keytab was generated with
ktpass -princ HTTP/is.k01.mydomain.com#MYDOMAIN.COM -pass ***** -mapuser MYDOMAIN\is.k01.kerb -pType KRB5_NT_PRINCIPAL -out c:\temp\is.k01.HTTP.keytab -crypto AES256-SHA1
as the .net documentation says.
I was not able to disallow use of rc4-hmac and allow only newer encoding, so i asked my infra department to generate new keytab with old rc4-hmac encoding.
This step has moved me further and I get this error instead: Request ticket server HTTP/is.k01.mydomain.com#MYDOMAIN.COM kvno 4 not found in keytab; keytab is likely out of date*
Which is very wierd because keytabs cannot get out of date, password has not been changed and was 100% valid one hour ago when the keytab was generated, and there is no information on web - "kvno 4 not found in keytab" fetch only 4 results in google.
**** EDIT
So finally I have managed to make it work :)
The issue with "kvno 4 not found in keytab" was in krb5.conf file, where I in favor of forcing aes encryption i have added lines
# default_tkt_enctypes = aes256-cts-hmac-sha1-96 aes256-cts-hmac-sha1-9
# default_tgs_enctypes = aes256-cts-hmac-sha1-96 aes256-cts-hmac-sha1-9
# permitted_enctypes = aes256-cts-hmac-sha1-96 aes256-cts-hmac-sha1-9
After I have commented them out, the authentication using Negotiate has started to work. I have tested the NTLM with .net 5 and it still does not work.
The krb5.conf file with which negotiate in docker container as build above works :
[appdefaults]
default_lifetime = 25hrs
krb4_convert = false
krb4_convert_524 = false
ksu = {
forwardable = false
}
pam = {
minimum_uid = 100
forwardable = true
}
pam-afs-session = {
minimum_uid = 100
}
[libdefaults]
default_realm = MYDOMAIN.COM
[realms]
MYDOMAIN.COM = {
kdc = DC02.MYDOMAIN.COM
default_domain = MYDOMAIN.COM
}
[domain_realm]
mydomain.com. = MYDOMAIN.COM
.mydomain.com. = MYDOMAIN.COM
[logging]
default = CONSOLE
default = SYSLOG:INFO
default = FILE:/var/log/krb5-default.log
kdc = CONSOLE
kdc = SYSLOG:INFO:DAEMON
kdc = FILE:/var/log/krb5-kdc.log
admin_server = SYSLOG:INFO
admin_server = DEVICE=/dev/tty04
admin_server = FILE:/var/log/krb5-kadmin.log
So the question now: Is there any way how to allow many services run negotiate protocol without adding each to spn by one, and manualy setting the browsers?
So at the moment every new web service must have:
setspn -S HTTP/mywebservice.mydomain.com mymachine
setspn -S HTTP/mywebservice#MYDOMAIN.COM mymachine
and must be allowed in internet explorer > settings > security > webs > Details > domain should be listed there
in firefox about:config > network.negotiate-auth.trusted-uris
chrome as far as i know takes internet explorer settings
i assume that internet explorer settings should be possible somehow update by the domain group policy.. anybody any idea how?
**** EDIT
I have tested wildcard in domain for negotiate settings in browsers and these are the results:
chrome: SUPPORTS *.k01.mydomain.com
ie: SUPPORTS *.k01.mydomain.com
firefox (73.0.1 (64-bit)): DOES NOT SUPPORT *.k01.mydomain.com - only full domain eg is.k01.mydomain.com
edge 44.18362.449.0 - dont know why but none of ie settings were propagated.. not working with *.k01.mydomain.com nor is.k01.mydomain.com
**** EDIT
I have started to use the win auth with negotiate, however I get some issues now in .net core
This code under IIS express shows user in form of MYDOMAIN\myuser:
var userId = string.Join(',', User?.Identities?.Select(c => c.Name)) ?? "?";
In linux it shows as myuser#mydomain.com
User.Indentities.First() under IIS express is WindowsIdentity and I can list all groups of the user
User.Indentities.First() under Linux is ClaimsIdentity with no group information
When I try to restrict it with group in IIS Express i get:
//Access granted
[Authorize(Roles = "MYDOMAIN\\GROUP1")]
//403
[Authorize(Roles = "MYDOMAIN\\GROUP_NOT_EXISTS")]
Linux kestrel with negotiate:
//403
[Authorize(Roles = "MYDOMAIN\\GROUP1")]
So it seems that negotiate in kestrel does not list groups properly. So i am going to investigate now, how to get WindowsIdentity in kestrel.

Answer 1

This article is a good example of misunderstanding how things work. I don't recommend to follow the way(like I did) author described here at all .
Instead, I would recommend learning about Kerberos authentication, how it works, what settings it requires. This article visualizes it good.
First,
If you profile http traffic coming from browser(user Fiddler, for example) you can find a TGS token in the second request.
If it starts with Negotiate TlR then you're doing auth over NTLM.
If it starts with Negotiate YII then you're doing auth over Kerberos.
Second,
Like David said before ASP.NET Core 3.1 doesn't support NTLM on Linux at all. So if you have TlR token and ntlm-gssapi mechanism you will get "No credentials were supplied, or the credentials were unavailable or inaccessible." error.
If you have TlR token and use default Kerberos mechanism you will get "An unsupported mechanism was requested."
Next,
The only way to get your app works well is to create SPNs and generate keytab correctly for Kerberos authentication. Unfortunately, this is not documented well. So, I gonna give an example here to make things more clear.
Let's say you have:
AD domain MYDOMAIN.COM
The web application with host webapp.webservicedomain.com. This can ends with mydomain.com, but not in my case.
Windows machine joined to AD with name mymachine.
Machine account MYDOMAIN\mymachine
Regarding the instructions described here you need to do:
Add new web service SPNs to the machine account:
setspn -S HTTP/webapp.webservicedomain.com mymachine
setspn -S HTTP/webapp#MYDOMAIN.COM mymachine
Use ktpass to generate a keytab file
ktpass -princ HTTP/webapp.webservicedomain.com#MYDOMAIN.COM -pass myKeyTabFilePassword -mapuser MYDOMAIN\mymachine$ -pType KRB5_NT_PRINCIPAL -out c:\temp\mymachine.HTTP.keytab -crypto AES256-SHA1*.
*Make sure MYDOMAIN\mymachine has AES256-SHA1 allowed in AD.
Finally,
After making all above things done and deploying the app into Linux container with keytab the Integrated Windows Authentication is supposed to worked well. My experiment showed you can use keytab wherever you want not only on the host with name "mymachine".

Answer 2

In dotnet runtime git they tell us that gss-ntlmssp is required for this to work even that it is not mentioned anyhow in the aspnet core documentation.
The 'gss-ntlmssp' package is a plug-in for supporting the NTLM protocol for the GSS-API. It supports both raw NTLM protocol as well as NTLM being used as the fallback from Kerberos to NTLM when 'Negotiate' (SPNEGO protocol) is being used. Ref: https://learn.microsoft.com/en-us/openspecs/windows_protocols/MS-SPNG/f377a379-c24f-4a0f-a3eb-0d835389e28a
From reading the discussion above and the image you posted, it appears that the application is trying to actually use NTLM instead of Kerberos. You can tell because the based64 encoded token starts with "T" instead of "Y".
ASP.NET Core server (Kestrel) does NOT support NTLM server-side on Linux at all. It only provides for 'Www-Authenticate: Negotiate' to be sent back to clients. And usually that means that Kerberos would be used. Negotiate can fall back to using NTLM. However, that doesn't work in ASP.NET Core except in .NET 5 which has not shipped yet.
Are you expecting your application to fall back to NTLM? If not, then perhaps the Kerberos environment is not completely set up. This can be caused by a variety of issues including the SPNs and Linux keytab files not being correct. It can also be caused by the client trying to use a username/password that is not part of the Kerberos realm.
This problem is being discussed here: https://github.com/dotnet/aspnetcore/issues/19397
I recommend the conversation continue in the aspnet core repo issue discussion.