(C) SharePoint -- Get Server Form Digest Value

Demonstrates how to get a server form digest value to be placed in the X-RequestDigest HTTP request header for POST, PUT, MERGE, and DELETE requests. A form digest value is typically valid for 1800 seconds (i.e. 30 minutes). This example persists the value to a file, and only requests a new form digest value if the existing one is near expiration.

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#include <C_CkFileAccess.h>
#include <C_CkXml.h>
#include <C_CkDateTime.h>
#include <C_CkHttp.h>
#include <C_CkHttpResponse.h>

void ChilkatSample(void)
    {
    HCkFileAccess fac;
    HCkXml xml;
    BOOL success;
    HCkDateTime dtExpire;
    HCkDateTime dtNow;
    const char *formDigestXmlFile;
    int tNow;
    int tExpire;
    HCkHttp http;
    const char *savedAccept;
    HCkHttpResponse resp;
    HCkXml xml2;
    int timeoutInSec;

    // This requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // First, let's see if we already have a persisted form digest value
    // that hasn't yet expired.
    fac = CkFileAccess_Create();
    xml = CkXml_Create();

    // My example code (below) persists the form digest XML in this format:
    // 
    // 	<savedFormDigestValue>
    // 	<d:ExpireDateTime>2017-04-12T20:46:39Z</d:ExpireDateTime>
    // 	<d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
    // 	</savedFormDigestValue>
    // 

    dtExpire = CkDateTime_Create();
    dtNow = CkDateTime_Create();

    formDigestXmlFile = "qa_data/sharepoint/savedFormDigestValue.xml";
    if (CkFileAccess_FileExists(fac,formDigestXmlFile) == TRUE) {

        CkXml_LoadXmlFile(xml,formDigestXmlFile);

        // Get the expire date/time
        CkDateTime_SetFromTimestamp(dtExpire,CkXml_getChildContent(xml,"d:ExpireDateTime"));

        // Get the current date/time
        CkDateTime_SetFromCurrentSystemTime(dtNow);

        // Get both times as Unix time values
        tNow = CkDateTime_GetAsUnixTime(dtNow,FALSE);
        tExpire = CkDateTime_GetAsUnixTime(dtExpire,FALSE);

        // If tNow >= tExpire, then fall through.
        // Otherwise, just use the cached digest value.
        if (tNow < tExpire) {
            printf("Cached digest value is not yet expired.\n");
            printf("X-RequestDigest: %s\n",CkXml_getChildContent(xml,"d:FormDigestValue"));
            CkFileAccess_Dispose(fac);
            CkXml_Dispose(xml);
            CkDateTime_Dispose(dtExpire);
            CkDateTime_Dispose(dtNow);
            return;
        }

    }

    // If we got to this point, the cached digest value either does not exist, or expired.

    http = CkHttp_Create();

    // If SharePoint Windows classic authentication is used, then set the 
    // Login, Password, LoginDomain, and NtlmAuth properties.
    CkHttp_putLogin(http,"SHAREPOINT_USERNAME");
    CkHttp_putPassword(http,"SHAREPOINT_PASSWORD");
    CkHttp_putLoginDomain(http,"SHAREPOINT_NTLM_DOMAIN");
    CkHttp_putNtlmAuth(http,TRUE);

    // The more common case is to use SharePoint Online authentication (via the SPOIDCRL cookie).
    // If so, do not set Login, Password, LoginDomain, and NtlmAuth, and instead
    // establish the cookie as shown at SharePoint Online Authentication

    // When creating, updating, and deleting SharePoint entities, we'll need
    // to first get the server's form digest value to send in the X-RequestDigest header.
    // This can be retrieved by making a POST request with an empty body to
    // http://<site url>/_api/contextinfo and extracting the value of the
    // d:FormDigestValue node in the XML that the contextinfo endpoint returns.

    // Apparently, SharePoint needs an "Accept" request header equal to "application/xml",
    // otherwise SharePoint will return an utterly incomprehensible and useless error message.
    savedAccept = CkHttp_ck_accept(http);
    CkHttp_putAccept(http,"application/xml");

    // Note: The last argument ("utf-8") is meaningless here because the body is empty.
    resp = CkHttp_PostXml(http,"https://SHAREPOINT_HTTPS_DOMAIN/_api/contextinfo","","utf-8");
    if (CkHttp_getLastMethodSuccess(http) != TRUE) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkFileAccess_Dispose(fac);
        CkXml_Dispose(xml);
        CkDateTime_Dispose(dtExpire);
        CkDateTime_Dispose(dtNow);
        CkHttp_Dispose(http);
        return;
    }

    // Restore the default Accept header
    CkHttp_putAccept(http,savedAccept);

    if (CkHttpResponse_getStatusCode(resp) != 200) {
        // A response status code not equal to 200 indicates failure.
        printf("Response status code = %d\n",CkHttpResponse_getStatusCode(resp));
        printf("Response body:\n");
        printf("%s\n",CkHttpResponse_bodyStr(resp));
        CkHttpResponse_Dispose(resp);
        CkFileAccess_Dispose(fac);
        CkXml_Dispose(xml);
        CkDateTime_Dispose(dtExpire);
        CkDateTime_Dispose(dtNow);
        CkHttp_Dispose(http);
        return;
    }

    CkXml_LoadXml(xml,CkHttpResponse_bodyStr(resp));
    CkHttpResponse_Dispose(resp);

    // The response XML looks like this:

    // <?xml version="1.0" encoding="utf-8" ?>
    // <d:GetContextWebInformation xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns:georss="http://www.georss.org/georss" xmlns:gml="http://www.opengis.net/gml" m:type="SP.ContextWebInformation">
    //     <d:FormDigestTimeoutSeconds m:type="Edm.Int32">1800</d:FormDigestTimeoutSeconds>
    //     <d:FormDigestValue>0x3059FFB920651834540F3E6792EA73F5746B302E953FF4E808E485DB1E6C2836C7CF924644995F092453B02A94DE14A7962674B7B16780AF16EAFB8C246BCDC7,12 Apr 2017 17:08:22 -0000</d:FormDigestValue>
    //     <d:LibraryVersion>15.0.4569.1000</d:LibraryVersion>
    //     <d:SiteFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:SiteFullUrl>
    //     <d:SupportedSchemaVersions m:type="Collection(Edm.String)">
    //         <d:element>14.0.0.0</d:element>
    //         <d:element>15.0.0.0</d:element>
    //     </d:SupportedSchemaVersions>
    //     <d:WebFullUrl>https://SHAREPOINT_HTTPS_DOMAIN</d:WebFullUrl>
    // </d:GetContextWebInformation>
    // 

    // Cache the digest value, and also an expiration time.  If this code is run again
    // before the digest expires, we'll just get it from the file.
    xml2 = CkXml_Create();

    CkXml_putTag(xml2,"savedFormDigestValue");
    CkXml_NewChild2(xml2,"d:FormDigestValue",CkXml_getChildContent(xml,"d:FormDigestValue"));

    timeoutInSec = CkXml_GetChildIntValue(xml,"d:FormDigestTimeoutSeconds");
    printf("Timeout in seconds = %d\n",timeoutInSec);

    // Convert this to an expire timestamp.
    // Let's make it expire 30 seconds prior to the actual timeout, just to be safe.
    if (timeoutInSec > 30) {
        timeoutInSec = timeoutInSec - 30;
    }

    CkDateTime_SetFromCurrentSystemTime(dtExpire);
    CkDateTime_AddSeconds(dtExpire,timeoutInSec);
    CkXml_NewChild2(xml2,"d:ExpireDateTime",CkDateTime_getAsTimestamp(dtExpire,FALSE));

    // Persist the digest and expire time to a file.
    CkXml_SaveXml(xml2,formDigestXmlFile);

    printf("Here is the new form digest value:\n");
    printf("X-RequestDigest: %s\n",CkXml_getChildContent(xml,"d:FormDigestValue"));


    CkFileAccess_Dispose(fac);
    CkXml_Dispose(xml);
    CkDateTime_Dispose(dtExpire);
    CkDateTime_Dispose(dtNow);
    CkHttp_Dispose(http);
    CkXml_Dispose(xml2);

    }