SOSBackupSliceKeyBag.c   [plain text]

/*
 * Copyright (c) 2015 Apple Inc. All Rights Reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */


// Our Header
#include <Security/SecureObjectSync/SOSBackupSliceKeyBag.h>


// Needed headers for implementation
#include "AssertMacros.h"
#include <utilities/SecCFWrappers.h>
#include <utilities/SecAKSWrappers.h>
#include <utilities/SecBuffer.h>
#include <utilities/SecCFError.h>
#include <utilities/der_set.h>
#include <utilities/der_plist_internal.h>
#include <Security/SecRandom.h>
#include <Security/SecureObjectSync/SOSPeerInfo.h>
#include <Security/SecureObjectSync/SOSPeerInfoCollections.h>
#include <Security/SecureObjectSync/SOSInternal.h>

#include <corecrypto/ccec.h>
#include <corecrypto/ccsha2.h>
#include <corecrypto/ccrng.h>

#include <limits.h>

#include "SOSInternal.h"

//
// MARK: Type creation
//

CFGiblisFor(SOSBackupSliceKeyBag);

const int kAKSBagSecretLength = 32;

struct __OpaqueSOSBackupSliceKeyBag {
    CFRuntimeBase           _base;

    CFDataRef               aks_bag;

    CFSetRef                peers;
    CFDictionaryRef         wrapped_keys;
};

static void SOSBackupSliceKeyBagDestroy(CFTypeRef aObj) {
    SOSBackupSliceKeyBagRef vb = (SOSBackupSliceKeyBagRef) aObj;

    CFReleaseNull(vb->aks_bag);
    CFReleaseNull(vb->peers);
    CFReleaseNull(vb->wrapped_keys);
}

static CFStringRef SOSBackupSliceKeyBagCopyFormatDescription(CFTypeRef aObj, CFDictionaryRef formatOptions) {
    SOSBackupSliceKeyBagRef vb = (SOSBackupSliceKeyBagRef) aObj;

    CFMutableStringRef description = CFStringCreateMutable(kCFAllocatorDefault, 0);

    CFStringAppendFormat(description, NULL, CFSTR("<SOSBackupSliceKeyBag@%p %ld"), vb, vb->peers ? CFSetGetCount(vb->peers) : 0);
    CFStringAppend(description, CFSTR(">"));

    return description;
}


//
// MARK: Encode/Decode
//

const uint8_t* der_decode_BackupSliceKeyBag(CFAllocatorRef allocator,
                                            SOSBackupSliceKeyBagRef* BackupSliceKeyBag, CFErrorRef *error,
                                            const uint8_t* der, const uint8_t *der_end) {
    if (der == NULL) return der;

    const uint8_t *result = NULL;
    SOSBackupSliceKeyBagRef vb = CFTypeAllocate(SOSBackupSliceKeyBag, struct __OpaqueSOSBackupSliceKeyBag, allocator);
    require_quiet(SecAllocationError(vb, error, CFSTR("View bag allocation failed")), fail);

    const uint8_t *sequence_end = NULL;
    der = ccder_decode_sequence_tl(&sequence_end, der, der_end);
    require_quiet(sequence_end == der_end, fail);

    der = der_decode_data(kCFAllocatorDefault, kCFPropertyListImmutable, &vb->aks_bag, error, der, sequence_end);
    vb->peers = SOSPeerInfoSetCreateFromArrayDER(kCFAllocatorDefault, &kSOSPeerSetCallbacks, error,
                                                 &der, der_end);
    der = der_decode_dictionary(kCFAllocatorDefault, kCFPropertyListImmutable, &vb->wrapped_keys, error, der, sequence_end);

    require_quiet(SecRequirementError(der == der_end, error, CFSTR("Extra space in sequence")), fail);

    if (BackupSliceKeyBag)
        CFTransferRetained(*BackupSliceKeyBag, vb);

    result = der;

fail:
    CFReleaseNull(vb);
    return result;
}

size_t der_sizeof_BackupSliceKeyBag(SOSBackupSliceKeyBagRef BackupSliceKeyBag, CFErrorRef *error) {
    size_t result = 0;

    size_t bag_size = der_sizeof_data(BackupSliceKeyBag->aks_bag, error);
    require_quiet(bag_size, fail);

    size_t peers_size = SOSPeerInfoSetGetDEREncodedArraySize(BackupSliceKeyBag->peers, error);
    require_quiet(peers_size, fail);

    size_t wrapped_keys_size = der_sizeof_dictionary(BackupSliceKeyBag->wrapped_keys, error);
    require_quiet(wrapped_keys_size, fail);

    result = ccder_sizeof(CCDER_CONSTRUCTED_SEQUENCE, bag_size + peers_size + wrapped_keys_size);

fail:
    return result;
}

uint8_t* der_encode_BackupSliceKeyBag(SOSBackupSliceKeyBagRef set, CFErrorRef *error,
                                      const uint8_t *der, uint8_t *der_end) {
    uint8_t *result = NULL;
    if (der_end == NULL) return der_end;

    require_quiet(SecRequirementError(set != NULL, error, CFSTR("Null set passed to encode")), fail);

    der_end = ccder_encode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, der_end, der,
              der_encode_data(set->aks_bag, error, der,
              SOSPeerInfoSetEncodeToArrayDER(set->peers, error, der,
              der_encode_dictionary(set->wrapped_keys, error, der, der_end))));

    require_quiet(der_end == der, fail);

    result = der_end;
fail:
    return result;
}


SOSBackupSliceKeyBagRef SOSBackupSliceKeyBagCreateFromData(CFAllocatorRef allocator, CFDataRef data, CFErrorRef *error) {
    SOSBackupSliceKeyBagRef result = NULL;
    SOSBackupSliceKeyBagRef decodedBag = NULL;

    const uint8_t *der = CFDataGetBytePtr(data);
    const uint8_t *der_end = der + CFDataGetLength(data);

    der = der_decode_BackupSliceKeyBag(allocator, &decodedBag, error, der, der_end);

    require_quiet(SecRequirementError(der == der_end, error, CFSTR("Didn't consume all data supplied")), fail);

    CFTransferRetained(result, decodedBag);

fail:
    CFReleaseNull(decodedBag);
    return result;
}

//
// MARK: Construction
//

bool SOSBSKBIsGoodBackupPublic(CFDataRef publicKey, CFErrorRef *error) {
    bool result = false;

    ccec_pub_ctx_decl_cp(SOSGetBackupKeyCurveParameters(), pub_key);

    int cc_result = ccec_compact_import_pub(SOSGetBackupKeyCurveParameters(), CFDataGetLength(publicKey), CFDataGetBytePtr(publicKey), pub_key);

    require_action_quiet(cc_result == 0, exit, SOSErrorCreate(kSOSErrorDecodeFailure, error, NULL, CFSTR("Unable to decode public key: %@"), publicKey));

    result = true;
exit:
    return result;

}


static CFDataRef SOSCopyECWrapped(CFDataRef publicKey, CFDataRef secret, CFErrorRef *error) {
    CFDataRef result = NULL;

    ccec_pub_ctx_decl_cp(SOSGetBackupKeyCurveParameters(), pub_key);

    int cc_result = ccec_compact_import_pub(SOSGetBackupKeyCurveParameters(), CFDataGetLength(publicKey), CFDataGetBytePtr(publicKey), pub_key);

    require_action_quiet(cc_result == 0, exit, SOSErrorCreate(kSOSErrorDecodeFailure, error, NULL, CFSTR("Unable to decode public key: %@"), publicKey));

    result = SOSCopyECWrappedData(pub_key, secret, error);

exit:
    return result;
}


static CFDictionaryRef SOSBackupSliceKeyBagCopyWrappedKeys(SOSBackupSliceKeyBagRef vb, CFDataRef secret, CFErrorRef *error) {
    CFDictionaryRef result = NULL;
    CFMutableDictionaryRef wrappedKeys = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);

    __block bool success = true;
    CFSetForEach(vb->peers, ^(const void *value) {
        SOSPeerInfoRef pi = (SOSPeerInfoRef) value;
        if (isSOSPeerInfo(pi)) {
            CFStringRef id = SOSPeerInfoGetPeerID(pi);
            CFDataRef backupKey = SOSPeerInfoCopyBackupKey(pi);

            if (backupKey) {
                CFDataRef wrappedKey = SOSCopyECWrapped(backupKey, secret, error);
                if (wrappedKey) {
                    CFDictionaryAddValue(wrappedKeys, id, wrappedKey);
                } else {
                    success = false;
                }
                CFReleaseNull(wrappedKey);
                CFReleaseNull(backupKey);
            }

        }
    });

    if (success)
        CFTransferRetained(result, wrappedKeys);

    CFReleaseNull(wrappedKeys);
    return result;
}

static bool SOSBackupSliceKeyBagCreateBackupBag(SOSBackupSliceKeyBagRef vb, CFErrorRef* error) {
    CFReleaseNull(vb->aks_bag);

    // Choose a random key.
    PerformWithBufferAndClear(kAKSBagSecretLength, ^(size_t size, uint8_t *buffer) {
        SecRandomCopyBytes(kSecRandomDefault, size, buffer);
        CFDataRef secret = CFDataCreateWithBytesNoCopy(kCFAllocatorDefault, buffer, size, kCFAllocatorNull);

        CFAssignRetained(vb->wrapped_keys, SOSBackupSliceKeyBagCopyWrappedKeys(vb, secret, error));
        CFAssignRetained(vb->aks_bag, SecAKSCopyBackupBagWithSecret(size, buffer, error));

        CFReleaseSafe(secret);
    });

    return vb->aks_bag != NULL;
}


CFDataRef SOSBSKBCopyEncoded(SOSBackupSliceKeyBagRef BackupSliceKeyBag, CFErrorRef* error) {
    CFDataRef result = NULL;
    CFMutableDataRef encoded = NULL;

    size_t encodedSize = der_sizeof_BackupSliceKeyBag(BackupSliceKeyBag, error);
    require_quiet(encodedSize, fail);

    encoded = CFDataCreateMutableWithScratch(kCFAllocatorDefault, encodedSize);
    require_quiet(SecAllocationError(encoded, error, CFSTR("Faild to create scratch")), fail);

    uint8_t *encode_to = CFDataGetMutableBytePtr(encoded);
    uint8_t *encode_to_end = encode_to + CFDataGetLength(encoded);
    require_quiet(encode_to == der_encode_BackupSliceKeyBag(BackupSliceKeyBag, error, encode_to, encode_to_end), fail);

    CFTransferRetained(result, encoded);

fail:
    CFReleaseSafe(encoded);
    return result;
}

static CFSetRef SOSBackupSliceKeyBagCreatePeerSet(CFAllocatorRef allocator, CFSetRef peers) {
    CFMutableSetRef result = CFSetCreateMutableForSOSPeerInfosByID(allocator);

    CFSetForEach(peers, ^(const void *value) {
        CFSetAddValue(result, value);
    });

    return result;
}

SOSBackupSliceKeyBagRef SOSBackupSliceKeyBagCreate(CFAllocatorRef allocator, CFSetRef peers, CFErrorRef* error) {
    SOSBackupSliceKeyBagRef result = NULL;
    SOSBackupSliceKeyBagRef vb = CFTypeAllocate(SOSBackupSliceKeyBag, struct __OpaqueSOSBackupSliceKeyBag, allocator);
    require_quiet(SecAllocationError(vb, error, CFSTR("View bag allocation failed")), fail);

    require_quiet(SecRequirementError(CFSetGetCount(peers) > 0, error, CFSTR("Need peers")), fail);

    vb->peers = SOSBackupSliceKeyBagCreatePeerSet(allocator, peers);
    vb->wrapped_keys = CFDictionaryCreateMutableForCFTypes(allocator);

    require_quiet(SOSBackupSliceKeyBagCreateBackupBag(vb, error), fail);

    CFTransferRetained(result, vb);

fail:
    CFReleaseNull(vb);
    return result;
}

SOSBackupSliceKeyBagRef SOSBackupSliceKeyBagCreateDirect(CFAllocatorRef allocator, CFDataRef aks_bag, CFErrorRef *error)
{
    SOSBackupSliceKeyBagRef result = NULL;
    SOSBackupSliceKeyBagRef vb = CFTypeAllocate(SOSBackupSliceKeyBag, struct __OpaqueSOSBackupSliceKeyBag, allocator);
    require_quiet(SecAllocationError(vb, error, CFSTR("View bag allocation failed")), fail);

    require_quiet(SecRequirementError(aks_bag, error, CFSTR("Need aks bag")), fail);

    vb->aks_bag = CFRetainSafe(aks_bag);
    vb->peers = CFSetCreateMutableForSOSPeerInfosByID(allocator);
    vb->wrapped_keys = CFDictionaryCreateMutableForCFTypes(allocator);

    CFTransferRetained(result, vb);

fail:
    CFReleaseNull(vb);
    return result;
}

//
// MARK: Use
//

bool SOSBSKBIsDirect(SOSBackupSliceKeyBagRef backupSliceKeyBag)
{
    return 0 == CFSetGetCount(backupSliceKeyBag->peers);
}

CFDataRef SOSBSKBCopyAKSBag(SOSBackupSliceKeyBagRef backupSliceKeyBag, CFErrorRef* error)
{
    return CFRetainSafe(backupSliceKeyBag->aks_bag);
}

CFSetRef SOSBSKBGetPeers(SOSBackupSliceKeyBagRef backupSliceKeyBag){
    return backupSliceKeyBag->peers;
}

static keybag_handle_t SOSBSKBLoadAndUnlockBagWithSecret(SOSBackupSliceKeyBagRef backupSliceKeyBag,
                                                           size_t secretSize, const uint8_t *secret,
                                                           CFErrorRef *error)
{
#if !TARGET_HAS_KEYSTORE
    return bad_keybag_handle;
#else
    keybag_handle_t result = bad_keybag_handle;
    keybag_handle_t bag_handle = bad_keybag_handle;

    require_quiet(SecRequirementError(backupSliceKeyBag->aks_bag, error,
                                      CFSTR("No aks bag to load")), exit);
    require_quiet(SecRequirementError(CFDataGetLength(backupSliceKeyBag->aks_bag) < INT_MAX, error,
                                      CFSTR("No aks bag to load")), exit);
    require_quiet(SecRequirementError(secretSize <= INT_MAX, error,
                                      CFSTR("secret too big")), exit);

    kern_return_t aks_result;
    aks_result = aks_load_bag(CFDataGetBytePtr(backupSliceKeyBag->aks_bag),
                              (int) CFDataGetLength(backupSliceKeyBag->aks_bag),
                              &bag_handle);
    require_quiet(SecKernError(aks_result, error,
                               CFSTR("aks_load_bag failed: %d"), aks_result), exit);

    aks_result = aks_unlock_bag(bag_handle, secret, (int) secretSize);
    require_quiet(SecKernError(aks_result, error,
                               CFSTR("failed to unlock bag: %d"), aks_result), exit);

    result = bag_handle;
    bag_handle = bad_keybag_handle;

exit:
    if (bag_handle != bad_keybag_handle) {
        (void) aks_unload_bag(bag_handle);
    }

    return result;
#endif
}

keybag_handle_t SOSBSKBLoadAndUnlockWithPeerIDAndSecret(SOSBackupSliceKeyBagRef backupSliceKeyBag,
                                                        CFStringRef peerID, CFDataRef peerSecret,
                                                        CFErrorRef *error)
{
    __block keybag_handle_t result = bad_keybag_handle;

    CFDataRef lookedUpData = CFDictionaryGetValue(backupSliceKeyBag->wrapped_keys, peerID);
    require_quiet(SecRequirementError(lookedUpData != NULL, error, CFSTR("%@ has no wrapped key in %@"), peerID, backupSliceKeyBag), exit);

    require_quiet(SOSPerformWithDeviceBackupFullKey(SOSGetBackupKeyCurveParameters(), peerSecret, error, ^(ccec_full_ctx_t fullKey) {
        SOSPerformWithUnwrappedData(fullKey, lookedUpData, error, ^(size_t size, uint8_t *buffer) {
            result = SOSBSKBLoadAndUnlockBagWithSecret(backupSliceKeyBag, size, buffer, error);
        });
    }), exit);

exit:
    return result;
}


keybag_handle_t SOSBSKBLoadAndUnlockWithPeerSecret(SOSBackupSliceKeyBagRef backupSliceKeyBag,
                                                   SOSPeerInfoRef peer, CFDataRef peerSecret,
                                                   CFErrorRef *error)
{
    return SOSBSKBLoadAndUnlockWithPeerIDAndSecret(backupSliceKeyBag, SOSPeerInfoGetPeerID(peer), peerSecret, error);
}

keybag_handle_t SOSBSKBLoadAndUnlockWithDirectSecret(SOSBackupSliceKeyBagRef backupSliceKeyBag,
                                                     CFDataRef secret,
                                                     CFErrorRef *error)
{
    keybag_handle_t result = bad_keybag_handle;
    require_quiet(SecRequirementError(SOSBSKBIsDirect(backupSliceKeyBag), error, CFSTR("Not direct bag")), exit);

    result = SOSBSKBLoadAndUnlockBagWithSecret(backupSliceKeyBag,
                                               CFDataGetLength(secret),
                                               CFDataGetBytePtr(secret),
                                               error);

exit:
    return result;
}