在自托管IdentityServer3 CustomGrant验证器中访问IOwinRequest

，可以通过以下步骤实现：

首先，需要在IdentityServer3 CustomGrant验证器中获取当前的IOwinContext。可以通过在CustomGrantValidator类中注入IOwinContext来实现。例如：

public class CustomGrantValidator : ICustomGrantValidator
{
    private readonly IOwinContext _context;

    public CustomGrantValidator(IOwinContext context)
    {
        _context = context;
    }

    public async Task<CustomGrantValidationResult> ValidateAsync(ValidatedTokenRequest request)
    {
        // 在这里可以访问IOwinRequest对象
        var owinRequest = _context.Request;

        // 执行自定义验证逻辑

        return new CustomGrantValidationResult();
    }
}

然后，需要在IdentityServer3的Startup类中配置CustomGrantValidator并注入IOwinContext。例如：

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        // 配置IdentityServer3

        // 注册CustomGrantValidator并注入IOwinContext
        app.UseIdentityServerBearerTokenAuthentication(new IdentityServerBearerTokenAuthenticationOptions
        {
            Provider = new CustomGrantValidatorProvider()
        });

        // 其他配置
    }
}

public class CustomGrantValidatorProvider : OAuthBearerAuthenticationProvider
{
    public override Task ValidateIdentity(OAuthValidateIdentityContext context)
    {
        // 注入IOwinContext
        var owinContext = context.OwinContext;

        // 注入CustomGrantValidator
        var customGrantValidator = new CustomGrantValidator(owinContext);

        // 注入CustomGrantValidator到IdentityServer3
        context.Options.AccessTokenProvider = new CustomGrantAccessTokenProvider(customGrantValidator);

        return Task.FromResult<object>(null);
    }
}

public class CustomGrantAccessTokenProvider : AuthenticationTokenProvider
{
    private readonly CustomGrantValidator _customGrantValidator;

    public CustomGrantAccessTokenProvider(CustomGrantValidator customGrantValidator)
    {
        _customGrantValidator = customGrantValidator;
    }

    public override async Task ReceiveAsync(AuthenticationTokenReceiveContext context)
    {
        // 执行CustomGrantValidator的验证逻辑
        var result = await _customGrantValidator.ValidateAsync(context.Ticket.Identity);

        // 处理验证结果
        if (result.IsError)
        {
            context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
            context.Response.Headers.Add("WWW-Authenticate", new[] { "Bearer error=\"" + result.Error + "\"" });
        }
        else
        {
            context.Ticket.Properties.IssuedUtc = result.IssuedUtc;
            context.Ticket.Properties.ExpiresUtc = result.ExpiresUtc;
            context.SetTicket(context.Ticket);
        }
    }
}

通过以上步骤，你可以在自托管IdentityServer3 CustomGrant验证器中访问IOwinRequest对象，并执行自定义的验证逻辑。请注意，以上代码仅为示例，实际实现可能需要根据具体情况进行调整。