/*++

Copyright (c) 1992-1997  Microsoft Corporation

Module Name:

    contexts.c

Abstract:

    Contains routines for manipulating SNMP community structures.

Environment:

    User Mode - Win32

Revision History:

    10-Feb-1997 DonRyan
        Rewrote to implement SNMPv2 support.

--*/
 
///////////////////////////////////////////////////////////////////////////////
//                                                                           //
// Include files                                                             //
//                                                                           //
///////////////////////////////////////////////////////////////////////////////

#include "globals.h"
#include "contexts.h"
#include "snmpthrd.h"

#define DYN_REGISTRY_UPDATE 1

///////////////////////////////////////////////////////////////////////////////
//                                                                           //
// Private procedures                                                        //
//                                                                           //
///////////////////////////////////////////////////////////////////////////////

BOOL
AddValidCommunity(
    LPWSTR pCommunity,
    DWORD dwAccess
    )

/*++

Routine Description:

    Adds valid community to list.

Arguments:

    pCommunity - pointer to community to add.

    dwAccess - access rights for community.

Return Values:

    Returns true if successful.

--*/

{
    BOOL fOk = FALSE;
    PCOMMUNITY_LIST_ENTRY pCLE = NULL;
    AsnOctetString CommunityOctets;
    
    // initialize octet string info
    CommunityOctets.length  = wcslen(pCommunity) * sizeof(WCHAR);
    CommunityOctets.stream  = (LPBYTE)pCommunity;
    CommunityOctets.dynamic = FALSE;

    // attempt to locate in list    
    if (FindValidCommunity(&pCLE, &CommunityOctets)) {
                    
        SNMPDBG((
            SNMP_LOG_TRACE, 
            "SNMP: SVC: updating community %s.\n",
            StaticUnicodeToString((LPWSTR)pCommunity)
            ));

        // update access rights
        pCLE->dwAccess = dwAccess;

        // success
        fOk = TRUE;

    } else {

        // allocate community structure
        if (AllocCLE(&pCLE, pCommunity)) {
                            
            SNMPDBG((
                SNMP_LOG_TRACE, 
                "SNMP: SVC: adding community %s.\n",
                CommunityOctetsToString(&(pCLE->Community), TRUE)
                ));

            // insert into valid communities list
            InsertTailList(&g_ValidCommunities, &pCLE->Link);

            // update access rights
            pCLE->dwAccess = dwAccess;

            // success
            fOk = TRUE;
        }
    }

    return fOk;
}


///////////////////////////////////////////////////////////////////////////////
//                                                                           //
// Public procedures                                                         //
//                                                                           //
///////////////////////////////////////////////////////////////////////////////

BOOL
AllocCLE(
    PCOMMUNITY_LIST_ENTRY * ppCLE,
    LPWSTR                  pCommunity
    )

/*++

Routine Description:

    Allocates community structure and initializes.

Arguments:

    ppCLE - pointer to receive pointer to entry.

    pCommunity - pointer to community string.

Return Values:

    Returns true if successful.

--*/

{
    BOOL fOk = FALSE;
    PCOMMUNITY_LIST_ENTRY pCLE = NULL;

    // attempt to allocate structure
    pCLE = AgentMemAlloc(sizeof(COMMUNITY_LIST_ENTRY));

    // validate
    if (pCLE != NULL) {
        
        // determine string length
        DWORD nBytes = wcslen(pCommunity) * sizeof(WCHAR);

        // allocate memory for string (include terminator)
        pCLE->Community.stream = SnmpUtilMemAlloc(nBytes + sizeof(WCHAR));

        // validate community string stream
        if (pCLE->Community.stream != NULL) {

            // set length of manager string
            pCLE->Community.length = nBytes;
    
            // set memory allocation flag 
            pCLE->Community.dynamic = TRUE;

            // transfer community string into octets
            wcscpy((LPWSTR)(pCLE->Community.stream), pCommunity);

            // success
            fOk = TRUE;

        } else {
            
            SNMPDBG((
                SNMP_LOG_ERROR,
                "SNMP: SVC: could not copy community string %s.\n",
                StaticUnicodeToString(pCommunity)
                ));

            // release 
            FreeCLE(pCLE);

            // re-init
            pCLE = NULL;            
        }

    } else {
        
        SNMPDBG((
            SNMP_LOG_ERROR,
            "SNMP: SVC: could not allocate context entry for %s.\n",
            StaticUnicodeToString(pCommunity)
            ));
    }

    // transfer
    *ppCLE = pCLE;

    return fOk;
}


BOOL 
FreeCLE(
    PCOMMUNITY_LIST_ENTRY pCLE
    )

/*++

Routine Description:

    Releases community structure.

Arguments:

    pCLE - pointer to community list entry to be freed.

Return Values:

    Returns true if successful.

--*/

{
    // validate pointer
    if (pCLE != NULL) {

        // release octet string contents
        SnmpUtilOctetsFree(&pCLE->Community);

        // release structure
        AgentMemFree(pCLE);
    }

    return TRUE;
}


BOOL
FindValidCommunity(
    PCOMMUNITY_LIST_ENTRY * ppCLE,
    AsnOctetString *        pCommunity
    )

/*++

Routine Description:

    Locates valid community in list.

Arguments:

    ppCLE - pointer to receive pointer to entry.

    pCommunity - pointer to community to find.

Return Values:

    Returns true if successful.

--*/

{
    PLIST_ENTRY pLE;
    PCOMMUNITY_LIST_ENTRY pCLE;

    // initialize
    *ppCLE = NULL;

    // obtain pointer to list head
    pLE = g_ValidCommunities.Flink;

    // process all entries in list
    while (pLE != &g_ValidCommunities) {

        // retrieve pointer to community structure
        pCLE = CONTAINING_RECORD(pLE, COMMUNITY_LIST_ENTRY, Link);

        // compare community string with entry
        if (!SnmpUtilOctetsCmp(&pCLE->Community, pCommunity)) {

            // transfer
            *ppCLE = pCLE;

            // success
            return TRUE;
        }

        // next entry
        pLE = pLE->Flink;
    }

    // failure
    return FALSE;
}


DWORD
ParsePermissionMask(
    DWORD bitMask
    )
/*++

Routine Description:

    Translates the permission mask from the bit-mask format (registry)
    into the internal constant value (constants from public\sdk\inc\snmp.h).
    The function works no longer if:
    - more than sizeof(DWORD)*8 permission values are defined
    - constant values (access policy) changes

Arguments:

    bit-mask.

Return Values:

    permission's constant value.

--*/
{
    DWORD dwPermission;

    for(dwPermission = 0; (bitMask & ((DWORD)(-1)^1)) != 0; bitMask>>=1, dwPermission++);

    return dwPermission;
}

#ifdef DYN_REGISTRY_UPDATE
LONG UpdateRegistry(
    HKEY hKey,
    LPWSTR wszBogus,
    LPWSTR wszCommunity
    )
/*++

Routine Description:

    Updates the registry configuration in order to be able to associate
    permission masks to each community:
                name            type        data
    old format: <whatever>      REG_SZ      community_name
    new format: community_name  REG_DWORD   permission_mask
Arguments:

    hKey - open handle to the key that contains the value
    szBogus - old format value name; useless data
    szCommunity - pointer to community name, as it was specified in the old format.

Return Values:

    Returns ERROR_SUCCESS if successful.

--*/
{
    LONG lStatus;
    DWORD dwDataType;

    // make sure the update was not tried (and breaked) before
    lStatus = RegQueryValueExW(
                hKey,
                wszCommunity,
                0,
                &dwDataType,
                NULL,
                NULL);

    // if no previous (breaked) update, convert community to the new format
    if (lStatus != ERROR_SUCCESS || dwDataType != REG_DWORD)
    {
        // permissions to be assigned to community
        DWORD dwPermissionMask;
        
        // all communities that are converted to new format at this point,
        // are converted to READ-ONLY permissions to tighten the security
        dwPermissionMask = 1 << SNMP_ACCESS_READ_ONLY;

        // set the new format value
        lStatus = RegSetValueExW(
                    hKey,
                    wszCommunity,
                    0,
                    REG_DWORD,
                    (CONST BYTE *)&dwPermissionMask,
                    sizeof(DWORD));

        if (lStatus != ERROR_SUCCESS)
            return lStatus;
    }

    // delete the old format value
    lStatus = RegDeleteValueW(
                hKey,
                wszBogus);

    return lStatus;
}
#endif


BOOL
LoadValidCommunities(
    BOOL bFirstCall
    )

/*++

Routine Description:

    Constructs list of valid communities.

Arguments:

    None.

Return Values:

    Returns true if successful.

--*/

{
    HKEY hKey;
    LONG lStatus;
    DWORD dwIndex;
    WCHAR wszName[MAX_PATH];  // get the UNICODE encoding for szName
    DWORD dwNameSize;
    DWORD dwDataType;
    WCHAR wszData[MAX_PATH];  // get the UNICODE encoding for szData
    DWORD dwDataSize;
    BOOL fPolicy;
    LPTSTR pszKey;
    BOOL fOk = FALSE;

    
    SNMPDBG((
        SNMP_LOG_TRACE, 
        "SNMP: SVC: loading valid communities.\n"
        ));

#ifdef _POLICY
    // we need to provide precedence to the parameters set through the policy
    fPolicy = TRUE;
#else
    fPolicy = FALSE;
#endif

    do
    {
        // if the policy is to be enforced, check the policy registry location first
        pszKey = fPolicy ? REG_POLICY_VALID_COMMUNITIES : REG_KEY_VALID_COMMUNITIES;

        // open registry subkey    
        lStatus = RegOpenKeyEx(
                    HKEY_LOCAL_MACHINE,
                    pszKey,
                    0,
#ifdef DYN_REGISTRY_UPDATE
                    bFirstCall ? KEY_READ | KEY_SET_VALUE : KEY_READ,
#else
                    KEY_READ,
#endif
                    &hKey
                    );

        // if the call succeeded or we were not checking the policy, break the loop
        if (lStatus == ERROR_SUCCESS || !fPolicy)
            break;

        // being at this point, this means we were checking for the policy parameters.
        // If and only if the policy is not defined (registry key is missing) we
        // reset the error, mark 'fPolicy already tried' and go back into the loop
        if (lStatus == ERROR_FILE_NOT_FOUND)
        {
            lStatus = ERROR_SUCCESS;
            fPolicy = FALSE;
        }
    } while (lStatus == ERROR_SUCCESS);


    // validate return code
    if (lStatus == ERROR_SUCCESS) {

        // initialize
        dwIndex = 0;

        // loop until error or end of list
        for (dwIndex = 0;
             lStatus == ERROR_SUCCESS; 
             dwIndex++)

        {
            // initialize buffer sizes
            dwNameSize = sizeof(wszName) / sizeof(wszName[0]); // size in number of WCHARs, not the size in bytes
            dwDataSize = sizeof(wszData); // size in number of bytes

            // read next value
            lStatus = RegEnumValueW(
                        hKey, 
                        dwIndex, 
                        wszName, 
                        &dwNameSize,
                        NULL, 
                        &dwDataType, 
                        (LPBYTE)wszData, 
                        &dwDataSize
                        );

            // validate return code
            if (lStatus == ERROR_SUCCESS) {

                // dynamically update values that are not of DWORD type
                if (dwDataType != REG_DWORD)
                {
#ifdef DYN_REGISTRY_UPDATE
                    if (dwDataType == REG_SZ)
                    {
                        // BUG# 638837, do not update ValidCommunities 
                        // registry format in case we're working with policy
                        if (bFirstCall && !fPolicy)
                        {
                            if(UpdateRegistry(hKey, wszName, wszData) == ERROR_SUCCESS)
                            {
                                SNMPDBG((
                                    SNMP_LOG_WARNING, 
                                    "SNMP: SVC: updated community registration\n"
                                ));

                                // current value has been deleted, need to keep the index
                                dwIndex--;
                                continue;
                            }
                        }
                        else
                        {
                            SNMPDBG((
                                SNMP_LOG_WARNING,
                                "SNMP: SVC: old format community to be considered with read-only right"));

                            wcscpy(wszName, wszData);
                            *(DWORD *)wszData = (1 << SNMP_ACCESS_READ_ONLY);
                        }
                    }
                    else
#endif
                    {
                        SNMPDBG((
                            SNMP_LOG_WARNING, 
                            "SNMP: SVC: wrong format in ValidCommunities[%d] registry entry\n",
                            dwIndex
                        ));
                        continue;
                    }
                }

                // add valid community to list with related permissions
                if (AddValidCommunity(wszName, ParsePermissionMask(*(DWORD *)wszData)))
                {

                    SNMPDBG((
                        SNMP_LOG_WARNING, 
                        "SNMP: SVC: rights set to %d for community '%s'\n",
                        *(DWORD *)wszData,
                        StaticUnicodeToString(wszName)
                    ));

                }
                else
                {
                    // reset status to reflect failure
                    lStatus = ERROR_NOT_ENOUGH_MEMORY;
                }
            
            }
            else if (lStatus == ERROR_NO_MORE_ITEMS)
            {
                // success
                fOk = TRUE; 
            }
        }
        RegCloseKey(hKey);
    } 
    else
        // it doesn't matter how the values are, the key has to exist,
        // so mark as bFirstCall in order to log an event if this is not true.
        bFirstCall = TRUE;  
    
    if (!fOk) {
            
        SNMPDBG((
            SNMP_LOG_ERROR, 
            "SNMP: SVC: error %d processing ValidCommunities subkey.\n",
            lStatus
            ));

        // report an event only for the first call (initialization of the service).
        // otherwise subsequent registry ops through regedit might flood the event log with
        // unsignificant records
        if (bFirstCall)
            // report event
            ReportSnmpEvent(
                SNMP_EVENT_INVALID_REGISTRY_KEY, 
                1, 
                &pszKey, 
                lStatus
                );
    }
    return fOk;
}


BOOL
UnloadValidCommunities(
    )

/*++

Routine Description:

    Destroys list of valid communities.

Arguments:

    None.

Return Values:

    Returns true if successful.

--*/

{
    PLIST_ENTRY pLE;
    PCOMMUNITY_LIST_ENTRY pCLE;

    // process entries until list is empty
    while (!IsListEmpty(&g_ValidCommunities)) {

        // extract next entry from head of list
        pLE = RemoveHeadList(&g_ValidCommunities);

        // retrieve pointer to community structure
        pCLE = CONTAINING_RECORD(pLE, COMMUNITY_LIST_ENTRY, Link);
 
        // release
        FreeCLE(pCLE);
    }

    return TRUE;
}