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Support remounting devices at startup with correct flags (#1216)
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* Support remounting devices at startup with correct flags

* Add missing force remount condition
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@mlw
mlw authored Nov 2, 2023
1 parent ea7e11f commit d2cbddd
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Showing 7 changed files with 180 additions and 85 deletions.
2 changes: 2 additions & 0 deletions Source/common/SNTCommonEnums.h
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Original file line number Diff line number Diff line change
Expand Up @@ -162,6 +162,8 @@ typedef NS_ENUM(NSInteger, SNTDeviceManagerStartupPreferences) {
SNTDeviceManagerStartupPreferencesNone,
SNTDeviceManagerStartupPreferencesUnmount,
SNTDeviceManagerStartupPreferencesForceUnmount,
SNTDeviceManagerStartupPreferencesRemount,
SNTDeviceManagerStartupPreferencesForceRemount,
};

#ifdef __cplusplus
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4 changes: 4 additions & 0 deletions Source/common/SNTConfigurator.m
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Original file line number Diff line number Diff line change
Expand Up @@ -644,6 +644,10 @@ - (SNTDeviceManagerStartupPreferences)onStartUSBOptions {
return SNTDeviceManagerStartupPreferencesUnmount;
} else if ([action isEqualToString:@"forceunmount"]) {
return SNTDeviceManagerStartupPreferencesForceUnmount;
} else if ([action isEqualToString:@"remount"]) {
return SNTDeviceManagerStartupPreferencesRemount;
} else if ([action isEqualToString:@"forceremount"]) {
return SNTDeviceManagerStartupPreferencesForceRemount;
} else {
return SNTDeviceManagerStartupPreferencesNone;
}
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4 changes: 2 additions & 2 deletions Source/santad/EventProviders/DiskArbitrationTestUtil.h
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@ NS_ASSUME_NONNULL_BEGIN
@interface MockDADisk : NSObject
@property(nonatomic) NSDictionary *diskDescription;
@property(nonatomic, readwrite) NSString *name;
@property(nonatomic) BOOL wasMounted;
@property(nonatomic) BOOL wasUnmounted;
@end

Expand All @@ -40,14 +41,13 @@ typedef void (^MockDADiskAppearedCallback)(DADiskRef ref);
NSMutableDictionary<NSString *, MockDADisk *> *insertedDevices;
@property(nonatomic, readwrite, nonnull)
NSMutableArray<MockDADiskAppearedCallback> *diskAppearedCallbacks;
@property(nonatomic) BOOL wasRemounted;
@property(nonatomic, nullable) dispatch_queue_t sessionQueue;

- (instancetype _Nonnull)init;
- (void)reset;

// Also triggers DADiskRegisterDiskAppearedCallback
- (void)insert:(MockDADisk *)ref bsdName:(NSString *)bsdName;
- (void)insert:(MockDADisk *)ref;

// Retrieve an initialized singleton MockDiskArbitration object
+ (instancetype _Nonnull)mockDiskArbitration;
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18 changes: 13 additions & 5 deletions Source/santad/EventProviders/DiskArbitrationTestUtil.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -40,11 +40,14 @@ - (void)reset {
[self.insertedDevices removeAllObjects];
[self.diskAppearedCallbacks removeAllObjects];
self.sessionQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
self.wasRemounted = NO;
}

- (void)insert:(MockDADisk *)ref bsdName:(NSString *)bsdName {
self.insertedDevices[bsdName] = ref;
- (void)insert:(MockDADisk *)ref {
if (!ref.diskDescription[@"DAMediaBSDName"]) {
[NSException raise:@"Missing DAMediaBSDName"
format:@"The MockDADisk is missing the DAMediaBSDName diskDescription key."];
}
self.insertedDevices[ref.diskDescription[@"DAMediaBSDName"]] = ref;

for (MockDADiskAppearedCallback callback in self.diskAppearedCallbacks) {
dispatch_sync(self.sessionQueue, ^{
Expand Down Expand Up @@ -110,8 +113,13 @@ void DADiskMountWithArguments(DADiskRef _Nonnull disk, CFURLRef __nullable path,
DADiskMountOptions options, DADiskMountCallback __nullable callback,
void *__nullable context,
CFStringRef __nullable arguments[_Nullable]) {
MockDiskArbitration *mockDA = [MockDiskArbitration mockDiskArbitration];
mockDA.wasRemounted = YES;
MockDADisk *mockDisk = (__bridge MockDADisk *)disk;
mockDisk.wasMounted = YES;

if (context) {
dispatch_semaphore_t sema = (__bridge dispatch_semaphore_t)context;
dispatch_semaphore_signal(sema);
}
}

DADiskRef __nullable DADiskCreateFromBSDName(CFAllocatorRef __nullable allocator,
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126 changes: 77 additions & 49 deletions Source/santad/EventProviders/SNTEndpointSecurityDeviceManager.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -47,34 +47,39 @@ - (void)logDiskDisappeared:(NSDictionary *)props;

@property DASessionRef diskArbSession;
@property(nonatomic, readonly) dispatch_queue_t diskQueue;
@property dispatch_semaphore_t startupUnmountSema;
@property dispatch_semaphore_t diskSema;

@end

void diskMountedCallback(DADiskRef disk, DADissenterRef dissenter, void *context) {
void DiskMountedCallback(DADiskRef disk, DADissenterRef dissenter, void *context) {
if (dissenter) {
DAReturn status = DADissenterGetStatus(dissenter);

NSString *statusString = (NSString *)DADissenterGetStatusString(dissenter);
IOReturn systemCode = err_get_system(status);
IOReturn subSystemCode = err_get_sub(status);
IOReturn errorCode = err_get_code(status);

LOGE(@"SNTEndpointSecurityDeviceManager: dissenter status codes: system: %d, subsystem: %d, "
@"err: %d; status: %s",
systemCode, subSystemCode, errorCode, [statusString UTF8String]);
@"err: %d; status: %@",
systemCode, subSystemCode, errorCode,
CFBridgingRelease(DADissenterGetStatusString(dissenter)));
}

if (context) {
dispatch_semaphore_t sema = (__bridge dispatch_semaphore_t)context;
dispatch_semaphore_signal(sema);
}
}

void diskAppearedCallback(DADiskRef disk, void *context) {
void DiskAppearedCallback(DADiskRef disk, void *context) {
NSDictionary *props = CFBridgingRelease(DADiskCopyDescription(disk));
if (![props[@"DAVolumeMountable"] boolValue]) return;
SNTEndpointSecurityDeviceManager *dm = (__bridge SNTEndpointSecurityDeviceManager *)context;

[dm logDiskAppeared:props];
}

void diskDescriptionChangedCallback(DADiskRef disk, CFArrayRef keys, void *context) {
void DiskDescriptionChangedCallback(DADiskRef disk, CFArrayRef keys, void *context) {
NSDictionary *props = CFBridgingRelease(DADiskCopyDescription(disk));
if (![props[@"DAVolumeMountable"] boolValue]) return;

Expand All @@ -85,7 +90,7 @@ void diskDescriptionChangedCallback(DADiskRef disk, CFArrayRef keys, void *conte
}
}

void diskDisappearedCallback(DADiskRef disk, void *context) {
void DiskDisappearedCallback(DADiskRef disk, void *context) {
NSDictionary *props = CFBridgingRelease(DADiskCopyDescription(disk));
if (![props[@"DAVolumeMountable"] boolValue]) return;

Expand All @@ -94,6 +99,21 @@ void diskDisappearedCallback(DADiskRef disk, void *context) {
[dm logDiskDisappeared:props];
}

void DiskUnmountCallback(DADiskRef disk, DADissenterRef dissenter, void *context) {
if (dissenter) {
LOGW(@"Unable to unmount device: %@", CFBridgingRelease(DADissenterGetStatusString(dissenter)));
} else if (disk) {
NSDictionary *diskInfo = CFBridgingRelease(DADiskCopyDescription(disk));
LOGI(@"Unmounted device: Model: %@, Vendor: %@, Path: %@",
diskInfo[(__bridge NSString *)kDADiskDescriptionDeviceModelKey],
diskInfo[(__bridge NSString *)kDADiskDescriptionDeviceVendorKey],
diskInfo[(__bridge NSString *)kDADiskDescriptionVolumePathKey]);
}

dispatch_semaphore_t sema = (__bridge dispatch_semaphore_t)context;
dispatch_semaphore_signal(sema);
}

NSArray<NSString *> *maskToMountArgs(uint32_t remountOpts) {
NSMutableArray<NSString *> *args = [NSMutableArray array];
if (remountOpts & MNT_RDONLY) [args addObject:@"rdonly"];
Expand All @@ -111,43 +131,29 @@ uint32_t mountArgsToMask(NSArray<NSString *> *args) {
uint32_t flags = 0;
for (NSString *i in args) {
NSString *arg = [i lowercaseString];
if ([arg isEqualToString:@"rdonly"])
if ([arg isEqualToString:@"rdonly"]) {
flags |= MNT_RDONLY;
else if ([arg isEqualToString:@"noexec"])
} else if ([arg isEqualToString:@"noexec"]) {
flags |= MNT_NOEXEC;
else if ([arg isEqualToString:@"nosuid"])
} else if ([arg isEqualToString:@"nosuid"]) {
flags |= MNT_NOSUID;
else if ([arg isEqualToString:@"nobrowse"])
} else if ([arg isEqualToString:@"nobrowse"]) {
flags |= MNT_DONTBROWSE;
else if ([arg isEqualToString:@"noowners"])
} else if ([arg isEqualToString:@"noowners"]) {
flags |= MNT_UNKNOWNPERMISSIONS;
else if ([arg isEqualToString:@"nodev"])
} else if ([arg isEqualToString:@"nodev"]) {
flags |= MNT_NODEV;
else if ([arg isEqualToString:@"-j"])
} else if ([arg isEqualToString:@"-j"]) {
flags |= MNT_JOURNALED;
else if ([arg isEqualToString:@"async"])
} else if ([arg isEqualToString:@"async"]) {
flags |= MNT_ASYNC;
else
} else {
LOGE(@"SNTEndpointSecurityDeviceManager: unexpected mount arg: %@", arg);
}
}
return flags;
}

void UnmountCallback(DADiskRef disk, DADissenterRef dissenter, void *context) {
if (dissenter) {
LOGW(@"Unable to unmount device: %@", CFBridgingRelease(DADissenterGetStatusString(dissenter)));
} else if (disk) {
NSDictionary *diskInfo = CFBridgingRelease(DADiskCopyDescription(disk));
LOGI(@"Unmounted device: Model: %@, Vendor: %@, Path: %@",
diskInfo[(__bridge NSString *)kDADiskDescriptionDeviceModelKey],
diskInfo[(__bridge NSString *)kDADiskDescriptionDeviceVendorKey],
diskInfo[(__bridge NSString *)kDADiskDescriptionVolumePathKey]);
}

dispatch_semaphore_t sema = (__bridge dispatch_semaphore_t)context;
dispatch_semaphore_signal(sema);
}

NS_ASSUME_NONNULL_BEGIN

@implementation SNTEndpointSecurityDeviceManager {
Expand Down Expand Up @@ -227,9 +233,15 @@ - (BOOL)remountUSBModeContainsFlags:(uint32_t)flags {
return (flags & requiredFlags) == requiredFlags;
}

// NB: Remount options are implemented as separate "unmount" and "mount"
// operations instead of using the "update"/MNT_UPDATE flag. This is because
// filesystems often don't support many transitions (e.g. RW to RO). Performing
// the two step process has a higher chance of succeeding.
- (void)performStartupTasks:(SNTDeviceManagerStartupPreferences)startupPrefs {
if (!self.blockUSBMount || (startupPrefs != SNTDeviceManagerStartupPreferencesUnmount &&
startupPrefs != SNTDeviceManagerStartupPreferencesForceUnmount)) {
startupPrefs != SNTDeviceManagerStartupPreferencesForceUnmount &&
startupPrefs != SNTDeviceManagerStartupPreferencesRemount &&
startupPrefs != SNTDeviceManagerStartupPreferencesForceRemount)) {
return;
}

Expand All @@ -241,8 +253,7 @@ - (void)performStartupTasks:(SNTDeviceManagerStartupPreferences)startupPrefs {
return;
}

self.startupUnmountSema = dispatch_semaphore_create(0);
int numUnmountAttempts = 0;
self.diskSema = dispatch_semaphore_create(0);

for (int i = 0; i < numMounts; i++) {
struct statfs *sfs = &mnts[i];
Expand All @@ -267,21 +278,36 @@ - (void)performStartupTasks:(SNTDeviceManagerStartupPreferences)startupPrefs {
}

DADiskUnmountOptions unmountOptions = kDADiskUnmountOptionDefault;
if (startupPrefs == SNTDeviceManagerStartupPreferencesForceUnmount) {
if (startupPrefs == SNTDeviceManagerStartupPreferencesForceUnmount ||
startupPrefs == SNTDeviceManagerStartupPreferencesForceRemount) {
unmountOptions = kDADiskUnmountOptionForce;
}

LOGI(@"Attempting to unmount device: '%s' mounted on '%s'", sfs->f_mntfromname,
sfs->f_mntonname);

DADiskUnmount(disk, unmountOptions, UnmountCallback, (__bridge void *)self.startupUnmountSema);
numUnmountAttempts++;
}
DADiskUnmount(disk, unmountOptions, DiskUnmountCallback, (__bridge void *)self.diskSema);

while (numUnmountAttempts-- > 0) {
if (dispatch_semaphore_wait(self.startupUnmountSema,
if (dispatch_semaphore_wait(self.diskSema,
dispatch_time(DISPATCH_TIME_NOW, 5 * NSEC_PER_SEC))) {
LOGW(@"An unmount attempt took longer than expected. Device may still be mounted.");
LOGW(
@"Unmounting '%s' mounted on '%s' took longer than expected. Device may still be mounted.",
sfs->f_mntfromname, sfs->f_mntonname);
continue;
}

if (startupPrefs == SNTDeviceManagerStartupPreferencesRemount ||
startupPrefs == SNTDeviceManagerStartupPreferencesForceRemount) {
uint32_t newMode = sfs->f_flags | mountArgsToMask(self.remountArgs);
LOGI(@"Attempting to mount device again changing flags: 0x%08x --> 0x%08x", sfs->f_flags,
newMode);

[self remount:disk mountMode:newMode semaphore:self.diskSema];

if (dispatch_semaphore_wait(self.diskSema,
dispatch_time(DISPATCH_TIME_NOW, 5 * NSEC_PER_SEC))) {
LOGW(@"Failed to remount device after unmounting: %s", sfs->f_mntfromname);
}
}
}
}
Expand Down Expand Up @@ -326,11 +352,11 @@ - (void)handleMessage:(Message &&)esMsg
}

- (void)enable {
DARegisterDiskAppearedCallback(_diskArbSession, NULL, diskAppearedCallback,
DARegisterDiskAppearedCallback(_diskArbSession, NULL, DiskAppearedCallback,
(__bridge void *)self);
DARegisterDiskDescriptionChangedCallback(_diskArbSession, NULL, NULL,
diskDescriptionChangedCallback, (__bridge void *)self);
DARegisterDiskDisappearedCallback(_diskArbSession, NULL, diskDisappearedCallback,
DiskDescriptionChangedCallback, (__bridge void *)self);
DARegisterDiskDisappearedCallback(_diskArbSession, NULL, DiskDisappearedCallback,
(__bridge void *)self);

[super subscribeAndClearCache:{
Expand Down Expand Up @@ -385,7 +411,7 @@ - (es_auth_result_t)handleAuthMount:(const Message &)m {
uint32_t newMode = mountMode | remountOpts;
LOGI(@"SNTEndpointSecurityDeviceManager: remounting device '%s'->'%s', flags (%u) -> (%u)",
eventStatFS->f_mntfromname, eventStatFS->f_mntonname, mountMode, newMode);
[self remount:disk mountMode:newMode];
[self remount:disk mountMode:newMode semaphore:nil];
}

if (self.deviceBlockCallback) {
Expand All @@ -395,14 +421,16 @@ - (es_auth_result_t)handleAuthMount:(const Message &)m {
return ES_AUTH_RESULT_DENY;
}

- (void)remount:(DADiskRef)disk mountMode:(uint32_t)remountMask {
- (void)remount:(DADiskRef)disk
mountMode:(uint32_t)remountMask
semaphore:(nullable dispatch_semaphore_t)sema {
NSArray<NSString *> *args = maskToMountArgs(remountMask);
CFStringRef *argv = (CFStringRef *)calloc(args.count + 1, sizeof(CFStringRef));
CFArrayGetValues((__bridge CFArrayRef)args, CFRangeMake(0, (CFIndex)args.count),
(const void **)argv);

DADiskMountWithArguments(disk, NULL, kDADiskMountOptionDefault, diskMountedCallback,
(__bridge void *)self, (CFStringRef *)argv);
DADiskMountWithArguments(disk, NULL, kDADiskMountOptionDefault, DiskMountedCallback,
(__bridge void *)sema, (CFStringRef *)argv);

free(argv);
}
Expand Down
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