mirror of https://github.com/oxen-io/session-ios
Matthew Chen
8 years ago
parent
6a76fed3c1
commit
5fcf89dff1
@ -0,0 +1,12 @@
|
||||
//
|
||||
// Copyright (c) 2017 Open Whisper Systems. All rights reserved.
|
||||
//
|
||||
|
||||
#import <Foundation/Foundation.h>
|
||||
|
||||
@interface NSData (Image)
|
||||
|
||||
+ (BOOL)isValidImageAtPath:(NSString *)filePath;
|
||||
- (BOOL)isValidImage;
|
||||
|
||||
@end
|
||||
@ -0,0 +1,139 @@
|
||||
//
|
||||
// Copyright (c) 2017 Open Whisper Systems. All rights reserved.
|
||||
//
|
||||
|
||||
#import "NSData+Image.h"
|
||||
|
||||
typedef NS_ENUM(NSInteger, ImageFormat) {
|
||||
ImageFormat_Unknown,
|
||||
ImageFormat_Png,
|
||||
ImageFormat_Gif,
|
||||
ImageFormat_Tiff,
|
||||
ImageFormat_Jpeg,
|
||||
ImageFormat_Bmp,
|
||||
};
|
||||
|
||||
@implementation NSData (Image)
|
||||
|
||||
+ (BOOL)isValidImageAtPath:(NSString *)filePath
|
||||
{
|
||||
NSError *error = nil;
|
||||
NSData *data = [NSData dataWithContentsOfFile:filePath options:NSMappedRead error:&error];
|
||||
if (error) {
|
||||
DDLogError(@"%@ could not read image data: %@", self.tag, error);
|
||||
}
|
||||
|
||||
return [data isValidImage];
|
||||
}
|
||||
|
||||
- (BOOL)isValidImage
|
||||
{
|
||||
// Don't trust the file extension; iOS (e.g. UIKit, Core Graphics) will happily
|
||||
// load a .gif with a .png file extension.
|
||||
//
|
||||
// Instead, use the "magic numbers" in the file data to determine the image format.
|
||||
ImageFormat imageFormat = [self guessImageFormat];
|
||||
if (imageFormat == ImageFormat_Gif) {
|
||||
return [self hasValidGifSize];
|
||||
} else if (imageFormat == ImageFormat_Unknown) {
|
||||
return NO;
|
||||
} else {
|
||||
return YES;
|
||||
}
|
||||
}
|
||||
|
||||
- (ImageFormat)guessImageFormat
|
||||
{
|
||||
const NSUInteger kTwoBytesLength = 2;
|
||||
if (self.length < kTwoBytesLength) {
|
||||
return ImageFormat_Unknown;
|
||||
}
|
||||
|
||||
unsigned char bytes[kTwoBytesLength];
|
||||
[self getBytes:&bytes range:NSMakeRange(0, kTwoBytesLength)];
|
||||
|
||||
unsigned char byte0 = bytes[0];
|
||||
unsigned char byte1 = bytes[1];
|
||||
|
||||
if (byte0 == 0x47 && byte1 == 0x49) {
|
||||
return ImageFormat_Gif;
|
||||
} else if (byte0 == 0x89 && byte1 == 0x50) {
|
||||
return ImageFormat_Png;
|
||||
} else if (byte0 == 0xff && byte1 == 0xd8) {
|
||||
return ImageFormat_Jpeg;
|
||||
} else if (byte0 == 0x42 && byte1 == 0x4d) {
|
||||
return ImageFormat_Bmp;
|
||||
} else if (byte0 == 0x4D && byte1 == 0x4D) {
|
||||
// Motorola byte order TIFF
|
||||
return ImageFormat_Tiff;
|
||||
} else if (byte0 == 0x49 && byte1 == 0x49) {
|
||||
// Intel byte order TIFF
|
||||
return ImageFormat_Tiff;
|
||||
}
|
||||
|
||||
return ImageFormat_Unknown;
|
||||
}
|
||||
|
||||
+ (BOOL)areByteArraysEqual:(NSUInteger)length left:(unsigned char *)left right:(unsigned char *)right
|
||||
{
|
||||
for (NSUInteger i = 0; i < length; i++) {
|
||||
if (left[i] != right[i]) {
|
||||
return NO;
|
||||
}
|
||||
}
|
||||
return YES;
|
||||
}
|
||||
|
||||
// Parse the GIF header to prevent the "GIF of death" issue.
|
||||
//
|
||||
// See: https://blog.flanker017.me/cve-2017-2416-gif-remote-exec/
|
||||
- (BOOL)hasValidGifSize
|
||||
{
|
||||
const NSUInteger kSignatureLength = 3;
|
||||
const NSUInteger kVersionLength = 3;
|
||||
const NSUInteger kWidthLength = 2;
|
||||
const NSUInteger kHeightLength = 2;
|
||||
const NSUInteger kPrefixLength = kSignatureLength + kVersionLength;
|
||||
const NSUInteger kBufferLength = kSignatureLength + kVersionLength + kWidthLength + kHeightLength;
|
||||
|
||||
if (self.length < kBufferLength) {
|
||||
return NO;
|
||||
}
|
||||
|
||||
unsigned char bytes[kBufferLength];
|
||||
[self getBytes:&bytes range:NSMakeRange(0, kBufferLength)];
|
||||
|
||||
unsigned char kGif87APrefix[kPrefixLength] = {
|
||||
0x47, 0x49, 0x46, 0x38, 0x37, 0x61,
|
||||
};
|
||||
unsigned char kGif89APrefix[kPrefixLength] = {
|
||||
0x47, 0x49, 0x46, 0x38, 0x39, 0x61,
|
||||
};
|
||||
if (![NSData areByteArraysEqual:kPrefixLength left:bytes right:kGif87APrefix]
|
||||
&& ![NSData areByteArraysEqual:kPrefixLength left:bytes right:kGif89APrefix]) {
|
||||
return NO;
|
||||
}
|
||||
NSUInteger width = ((NSUInteger)bytes[kPrefixLength + 0]) | (((NSUInteger)bytes[kPrefixLength + 1] << 8));
|
||||
NSUInteger height = ((NSUInteger)bytes[kPrefixLength + 2]) | (((NSUInteger)bytes[kPrefixLength + 3] << 8));
|
||||
|
||||
// We need to ensure that the image size is "reasonable".
|
||||
// We impose an arbitrary "very large" limit on image size
|
||||
// to eliminate harmful values.
|
||||
const NSUInteger kMaxValidSize = 1 << 18;
|
||||
|
||||
return (width > 0 && width < kMaxValidSize && height > 0 && height < kMaxValidSize);
|
||||
}
|
||||
|
||||
#pragma mark - Logging
|
||||
|
||||
+ (NSString *)tag
|
||||
{
|
||||
return [NSString stringWithFormat:@"[%@]", self.class];
|
||||
}
|
||||
|
||||
- (NSString *)tag
|
||||
{
|
||||
return self.class.tag;
|
||||
}
|
||||
|
||||
@end
|
||||
Loading…
Reference in New Issue