Create a custom policy file

Copied from MOSS 2007 and Code Access Security

The Microsoft one is pretty outdated: Microsoft Windows SharePoint Services and Code Access Security

1. Go to the following location on the server:

LocalDrive:\Program Files\Common Files\Microsoft Shared\web server extensions\12\CONFIG

2. Make a copy of wss_minimaltrust.config and rename it wss_customtrust.config.
3. Open wss_customtrust.config file using any text editor.
4. Under the <SecurityClasses> element, add a reference to the SharePointPermissions class as follows:

<SecurityClass Name="SharePointPermission" Description="Microsoft.SharePoint.Security.SharePointPermission, Microsoft.SharePoint.Security, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c." />

5. Search for the <PermissionSet> tag where the name attribute equals ASP.NET. If you couldn't find that <PermissionSet> tag, locate the one that has SPRestricted in the name attribute.
6. Copy the entire tag and all of its children, and paste a copy of it immediately below the one you copied.
7. Change the name of the PermissionSet element from ASP.NET (or SPRestricted) to CustomTrust.

Before:

<PermissionSet class="NamedPermissionSet" version="1" Name="SPRestricted">

After:

<PermissionSet class="NamedPermissionSet" version="1" Name="CustomTrust">

8. Add the following <IPermission> node to the <PermissionSet> element where the name attribute equals CustomTrust:

<IPermission class="SharePointPermission" version="1" ObjectModel="True" />

Therefore, the resulting customized <PermissionSet> will look as follows:

<PermissionSet class="NamedPermissionSet" version="1" Name="CustomTrust">

<IPermission class="AspNetHostingPermission" version="1" Level="Minimal" />

<IPermission class="SecurityPermission" version="1" Flags="Execution" />

<IPermission class="WebPartPermission" version="1" Connections="True" />

<IPermission class="SharePointPermission" version="1" ObjectModel="True" /> </PermissionSet>

9. Once you define the customized element, you must create a code group to specify when the CLR should apply the permission set. (For details, see the original Microsoft article). Locate <CodeGroup> tag where the class attribute equals FirstMatchCodeGroup and copy following CodeGroup immediately below it:

<CodeGroup class="UnionCodeGroup"
version="1"
PermissionSetName="CustomTrust">
<IMembershipCondition class="UrlMembershipCondition"
version="1"
Url="$AppDirUrl$/bin/*" />
</CodeGroup>

The membership condition for this new code group is based on URL membership and the URL points to the bin directory. The permissions will be applied to all the assemblies in the bin directory of the current application. You can also use strong name membership but then the permissions will be applied only to one assembly. For example, if I have written a web service and I wanted to assign permissions to my assembly only, I would use strong name membership. Copy following code immediately below the <CodeGroup> tag where the class attribute equals FirstMatchCodeGroup, if you want to use strong name membership:

<CodeGroup class="UnionCodeGroup"
version="1"
PermissionSetName="CustomTrust">
<IMembershipCondition class="StrongNameMembershipCondition"
version="1"
PublicKeyBlob="0x0024000004800000940000000602000000
2400005253413100040000010001004"
Name="UploadService" />
</CodeGroup>

Replace PublicKeyBlob value with your own value and change the name of the assembly in the Name attribute. Name attribute contains the name of the assembly. To retrieve the public key blob for an assembly, use the secutil.exe tool. Please note that publickeyblob is different from publickeytoken. Secutil.exe is located in the following folder:

LocalDrive:\Program Files\Microsoft Visual Studio 8\SDK\v2.0\Bin

To retrieve the public key blob for your assembly, either copy the secutil.exe tool to the folder that contains your assembly else provide exact path to the assembly in the command, and run the tool as follows:

secutil.exe -hex -s UploadService.dll > blob.txt

UploadService.dll is the name of the assembly. This command will create a text file named blob.txt. Open blob.txt and copy the public key and paste it in the publickeyblob attribute.
10. Save and close the file. The policy file is ready to use.
11. Open the web.config file for the virtual server where you have deployed your component and add the following <trustlevel> tag to the SecurityPolicy element:
<trustLevel name="WSS_Custom" policyFile="LocalDrive:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\config\wss_customtrust.config" />

Virtual Directories for web applications are located in the following folder:

LocalDrive:\Inetpub\wwwroot\wss\VirtualDirectories

Suppose I want to deploy my web service in the web application configured at port 17316. The URL of that application would be http://localhost:17316 and its virtual directory will be:

LocalDrive:\Inetpub\wwwroot\wss\VirtualDirectories\17315

Create a bin folder in this path and copy your assembly to the bin folder. The web.config for this virtual server will be located in the following folder:

LocalDrive:\Inetpub\wwwroot\wss\VirtualDirectories\17315

In the web.config file, change the <trust> tag so that it refers to the newly defined trust level.

<trust level="WSS_Custom" originUrl="" />

12. Save and close the web.config file.
13. Restart IIS to apply the custom policy to the specified virtual server.