Add -SkipHeaderValidation switch to Invoke-WebRequest and Invoke-RestMethod to support adding headers without validating the header value. (#4085)

* Add -SkipHeaderValidation switch to Invoke-WebRequest and Invoke-RestMethod to support adding headers without validating the header value.

* Fix whitespace

src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/CoreCLR/WebRequestPSCmdlet.CoreClr.cs

@@ -58,12 +58,21 @@ namespace Microsoft.PowerShell.Commands
         /// CoreCLR (HTTPClient) does not have this behavior so web requests that work on
         /// PowerShell/FullCLR can fail with PowerShell/CoreCLR.  To provide compatibility,
         /// we'll detect requests with an Authorization header and automatically strip
-        /// the header when the first redirect occurs. This switch turns off this logic for 
+        /// the header when the first redirect occurs. This switch turns off this logic for
         /// edge cases where the authorization header needs to be preserved across redirects.
         /// </remarks>
         [Parameter]
         public virtual SwitchParameter PreserveAuthorizationOnRedirect { get; set; }
 
+        /// <summary>
+        /// gets or sets the SkipHeaderValidation property
+        /// </summary>
+        /// <remarks>
+        /// This property adds headers to the request's header collection without validation.
+        /// </remarks>
+        [Parameter]
+        public virtual SwitchParameter SkipHeaderValidation { get; set; }
+
         #region Abstract Methods
 
         /// <summary>
@@ -240,14 +249,22 @@ namespace Microsoft.PowerShell.Commands
                     }
                     else
                     {
-                        if (stripAuthorization 
-                            && 
+                        if (stripAuthorization
+                            &&
                             String.Equals(entry.Key, HttpKnownHeaderNames.Authorization.ToString(), StringComparison.OrdinalIgnoreCase)
                         )
                         {
                             continue;
                         }
-                        request.Headers.Add(entry.Key, entry.Value);
+
+                        if (SkipHeaderValidation)
+                        {
+                            request.Headers.TryAddWithoutValidation(entry.Key, entry.Value);
+                        }
+                        else
+                        {
+                            request.Headers.Add(entry.Key, entry.Value);
+                        }
                     }
                 }
             }

test/powershell/Modules/Microsoft.PowerShell.Utility/WebCmdlets.Tests.ps1

@@ -184,6 +184,49 @@ function ExecuteRedirectRequest
     return $result
 }
 
+# This function calls either Invoke-WebRequest or Invoke-RestMethod with the given uri
+# using the custum headers and the  optional SkipHeaderValidation switch.
+function ExecuteRequestWithCustomHeaders
+{
+    param (
+        [Parameter(Mandatory)]
+        [string]
+        $Uri,
+
+        [ValidateSet('Invoke-WebRequest', 'Invoke-RestMethod')]
+        [string] $Cmdlet = 'Invoke-WebRequest',
+
+        [Parameter(Mandatory)]
+        [ValidateNotNull()]
+        [Hashtable] $Headers,
+
+        [switch] $SkipHeaderValidation
+    )
+    $result = [PSObject]@{Output = $null; Error = $null; Content = $null}
+
+    try
+    {
+        if ($Cmdlet -eq 'Invoke-WebRequest')
+        {
+            $result.Output = Invoke-WebRequest -Uri $Uri -TimeoutSec 5 -Headers $Headers -SkipHeaderValidation:$SkipHeaderValidation.IsPresent
+            $result.Content = $result.Output.Content | ConvertFrom-Json
+        }
+        else
+        {
+            $result.Output = Invoke-RestMethod -Uri $Uri -TimeoutSec 5 -Headers $Headers -SkipHeaderValidation:$SkipHeaderValidation.IsPresent
+            # NOTE: $result.Output should already be a PSObject (Invoke-RestMethod converts the returned json automatically)
+            # so simply reference $result.Output
+            $result.Content = $result.Output
+        }
+    }
+    catch
+    {
+        $result.Error = $_
+    }
+
+    return $result
+}
+
 <#
     Defines the list of redirect codes to test as well as the
     expected Method when the redirection is handled.
@@ -662,6 +705,35 @@ Describe "Invoke-WebRequest tests" -Tags "Feature" {
 
     #endregion Redirect tests
 
+    #region SkipHeaderVerification Tests
+
+    It "Verifies Invoke-WebRequest default header handling with no errors" {
+        $headers = @{"If-Match" = "*"}
+        $response = ExecuteRequestWithCustomHeaders -Uri "http://localhost:8080/PowerShell?test=echo" -headers $headers
+
+        $response.Error | Should BeNullOrEmpty
+        $response.Content.Headers -contains "If-Match" | Should Be $true
+    }
+
+    It "Verifies Invoke-WebRequest default header handling reports an error is returned for an invalid If-Match header value" {
+        $headers = @{"If-Match" = "12345"}
+        $response = ExecuteRequestWithCustomHeaders -Uri "http://localhost:8080/PowerShell?test=echo" -headers $headers
+
+        $response.Error | Should Not BeNullOrEmpty
+        $response.Error.FullyQualifiedErrorId | Should Be "System.FormatException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand"
+        $response.Error.Exception.Message | Should Be "The format of value '12345' is invalid."
+    }
+
+    It "Verifies Invoke-WebRequest header handling does not report an error when using -SkipHeaderValidation" {
+        $headers = @{"If-Match" = "12345"}
+        $response = ExecuteRequestWithCustomHeaders -Uri "http://localhost:8080/PowerShell?test=echo" -headers $headers -SkipHeaderValidation
+
+        $response.Error | Should BeNullOrEmpty
+        $response.Content.Headers -contains "If-Match" | Should Be $true
+    }
+
+    #endregion SkipHeaderVerification Tests
+
     BeforeEach {
         if ($env:http_proxy) {
             $savedHttpProxy = $env:http_proxy
@@ -1124,6 +1196,35 @@ Describe "Invoke-RestMethod tests" -Tags "Feature" {
 
     #endregion Redirect tests
 
+    #region SkipHeaderVerification tests
+
+    It "Verifies Invoke-RestMethod default header handling with no errors" {
+        $headers = @{"If-Match" = "*"}
+        $response = ExecuteRequestWithCustomHeaders -Uri "http://localhost:8081/PowerShell?test=echo" -headers $headers -Cmdlet "Invoke-RestMethod"
+
+        $response.Error | Should BeNullOrEmpty
+        $response.Content.Headers -contains "If-Match" | Should Be $true
+    }
+
+    It "Verifies Invoke-RestMethod default header handling reports an error is returned for an invalid If-Match header value" {
+        $headers = @{"If-Match" = "12345"}
+        $response = ExecuteRequestWithCustomHeaders -Uri "http://localhost:8081/PowerShell?test=echo" -headers $headers -Cmdlet "Invoke-RestMethod"
+
+        $response.Error | Should Not BeNullOrEmpty
+        $response.Error.FullyQualifiedErrorId | Should Be "System.FormatException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand"
+        $response.Error.Exception.Message | Should Be "The format of value '12345' is invalid."
+    }
+
+    It "Verifies Invoke-RestMethod header handling does not report an error when using -SkipHeaderValidation" {
+        $headers = @{"If-Match" = "12345"}
+        $response = ExecuteRequestWithCustomHeaders -Uri "http://localhost:8081/PowerShell?test=echo" -headers $headers -SkipHeaderValidation -Cmdlet "Invoke-RestMethod"
+
+        $response.Error | Should BeNullOrEmpty
+        $response.Content.Headers -contains "If-Match" | Should Be $true
+    }
+
+    #endregion SkipHeaderVerification tests
+
     BeforeEach {
         if ($env:http_proxy) {
             $savedHttpProxy = $env:http_proxy

test/tools/Modules/HttpListener/HttpListener.psm1

@@ -134,6 +134,13 @@ Function Start-HTTPListener {
                             $contentType = $queryItems["contenttype"]
                             $output = $queryItems["output"]
                         }
+
+                        # Echo the request as the output.
+                        "echo"
+                        {
+                            Write-Verbose -Message "Echo request"
+                            $output = $request | ConvertTo-Json -Depth 6
+                        }
                         
                         <# 
                             This test provides support for multiple redirection types as well as a custom