objective-c 如何在 Cocoa 中创建字符串的 MD5 哈希？

How do I create an MD5 Hash of a string in Cocoa?

提问by demonslayer319

I know SHA-1 is preferred, but this project requires I use MD5.

我知道 SHA-1 是首选，但这个项目需要我使用 MD5。

#include <openssl/md5.h>

- (NSString*) MD5Hasher: (NSString*) query {
    NSData* hashed = [query dataUsingEncoding:NSUTF8StringEncoding];
    unsigned char *digest = MD5([hashed bytes], [hashed length], NULL);
    NSString *final = [NSString stringWithUTF8String: (char *)digest];
    return final;
}

I got this code from an answer to another similar question on StackOverflow, but I get the following error from GDB when the program breaks at return final;

我从 StackOverflow 上另一个类似问题的答案中得到了这段代码，但是当程序在return final时中断时，我从 GDB 得到以下错误；

(gdb) p digest
 = (unsigned char *) 0xa06310e4 "06b0/66^1\b\a/9054"
(gdb) po final
Cannot access memory at address 0x0
(gdb) po digest

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0xb0623630
0x98531ed7 in objc_msgSend ()
The program being debugged was signaled while in a function called from GDB.
GDB has restored the context to what it was before the call.
To change this behavior use "set unwindonsignal off"
Evaluation of the expression containing the function
(_NSPrintForDebugger) will be abandoned.

I can't make any sense of it.

我无法理解。

回答by Grant Paul

This is the category I use:

这是我使用的类别：

NSString+MD5.h

NSString+MD5.h

@interface NSString (MD5)

- (NSString *)MD5String;

@end

NSString+MD5.m

NSString+MD5.m

#import <CommonCrypto/CommonDigest.h>

@implementation NSString (MD5)

- (NSString *)MD5String {
    const char *cStr = [self UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5( cStr, (CC_LONG)strlen(cStr), result );

    return [NSString stringWithFormat:
        @"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
        result[0], result[1], result[2], result[3], 
        result[4], result[5], result[6], result[7],
        result[8], result[9], result[10], result[11],
        result[12], result[13], result[14], result[15]
    ];  
}

@end

Usage

用法

NSString *myString = @"test";
NSString *md5 = [myString MD5String]; // returns NSString of the MD5 of test

回答by Peter Hosey

cdespinosa and irsk have already shown you your actual problem, so let me go through your GDB transcript:

cdespinosa 和 irsk 已经向您展示了您的实际问题，让我来看看您的 GDB 成绩单：

(gdb) p digest
 = (unsigned char *) 0xa06310e4 "06b0/66^1\b\a/9054"

(gdb) p digest
 = (unsigned char *) 0xa06310e4 "06b0/66^1\b\a/9054"

You've printed digestas a C string. You can see here that this string is raw bytes; hence all the octal escapes (e.g., \020, \225) and the couple of punctuation characters (/and ^). It is not the printable ASCII hexadecimal representation you were expecting. You're lucky that there were no zero bytes in it; otherwise, you would not have printed the entire hash.

您已打印digest为 C 字符串。你可以在这里看到这个字符串是原始字节；因此所有的八进制转义（例如\020，\225）和几个标点字符（/和^）。它不是您期望的可打印 ASCII 十六进制表示。你很幸运，里面没有零字节；否则，您就不会打印整个哈希。

(gdb) po final
Cannot access memory at address 0x0

(gdb) po final
Cannot access memory at address 0x0

finalis nil. This makes sense, as your string above isn't valid UTF-8; again, it's just raw data bytes. stringWithUTF8String:requires a UTF-8-encoded text string; you didn't give it one, so it returned nil.

final是nil。这是有道理的，因为上面的字符串不是有效的 UTF-8；同样，它只是原始数据字节。stringWithUTF8String:需要 UTF-8 编码的文本字符串；你没有给它一个，所以它返回了nil。

For passing raw data around, you'd use NSData. In this case, I think you want the hex representation, so you'll need to create that yourself the way irsk showed you.

为了传递原始数据，您可以使用 NSData。在这种情况下，我认为您需要十六进制表示，因此您需要按照 irsk 向您展示的方式自行创建。

Finally, consider how lucky you are that your input didn't hash to a valid UTF-8 string. If it had, you wouldn't have noticed this problem. You may want to construct a unit test for this hash method with this input.

最后，考虑一下您的输入没有散列为有效的 UTF-8 字符串是多么幸运。如果有，你就不会注意到这个问题。您可能希望使用此输入为此哈希方法构建单元测试。

(gdb) po digest

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0xb0623630
0x98531ed7 in objc_msgSend ()

(gdb) po digest

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0xb0623630
0x98531ed7 in objc_msgSend ()

Your program crashed (specific problem: “bad access”, “invalid address”) in objc_msgSend. This is because digesteither is not a Cocoa/CF object at all or was one but was freed. In this case, it's because digestis not a Cocoa object; it is a C array of bytes, as shown by your p digestline above.

您的程序在objc_msgSend. 这是因为digest要么根本不是 Cocoa/CF 对象，要么是一个对象但已被释放。在这种情况下，是因为digest不是 Cocoa 对象；它是一个 C 字节数组，如p digest上面的行所示。

Remember, Objective-C is a superset of C. All of C exists unchanged in it. That means there are C arrays (e.g., char []) and Cocoa's NSArrays side by side. Moreover, since NSArray comes from the Cocoa framework, not the Objective-C language, there's no way to make NSArray objects interchangeable with C arrays: You can't use the subscript operator on Cocoa arrays, and you can't send?Objective-C messages to C arrays.

请记住，Objective-C 是 C 的超集。所有 C 都不变地存在于其中。这意味着有 C 数组（例如，char []）和 Cocoa 的 NSArrays 并排。而且，由于 NSArray 来自 Cocoa 框架，而不是 Objective-C 语言，所以没有办法让 NSArray 对象与 C 数组互换：你不能在 Cocoa 数组上使用下标运算符，你也不能发送？目标- C 消息到 C 数组。

回答by Peter Lapisu

Facebook uses this

Facebook 使用这个

#import <CommonCrypto/CommonDigest.h>

---

---

+ (NSString*)md5HexDigest:(NSString*)input {
    const char* str = [input UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5(str, strlen(str), result);

    NSMutableString *ret = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH*2];
    for(int i = 0; i<CC_MD5_DIGEST_LENGTH; i++) {
        [ret appendFormat:@"%02x",result[i]];
    }
    return ret;
}

Or instance method

或者实例方法

- (NSString *)md5 {
    const char* str = [self UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5(str, (CC_LONG)strlen(str), result);

    NSMutableString *ret = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH*2];
    for(int i = 0; i<CC_MD5_DIGEST_LENGTH; i++) {
        [ret appendFormat:@"%02x",result[i]];
    }
    return ret;
}

回答by Nazir

I had used this method:

我曾经使用过这种方法：

NSString+MD5.h

NSString+MD5.h

@interface NSString (MD5)

- (NSString *)MD5;

@end

NSString+MD5.m

NSString+MD5.m

#import "NSString+MD5.h"
#import <CommonCrypto/CommonDigest.h>

@implementation NSString (MD5)

- (NSString *)MD5 {

    const char * pointer = self.UTF8String;
    unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];

    CC_MD5(pointer, (CC_LONG)strlen(pointer), md5Buffer);

    NSMutableString * string = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
        [string appendFormat:@"%02x", md5Buffer[i]];
    }

    return string;
}

@end

Usage:

用法：

NSString * myString = @"test";
NSString * md5 = [myString MD5];

回答by cdespinosa

I believe that digest is a pointer to a raw binary hash. In the next line you're attempting to interpret it as a UTF-8 string, but it is most likely not to contain legal UTF-8-encoded character sequences.

我相信摘要是指向原始二进制哈希的指针。在下一行中，您尝试将其解释为 UTF-8 字符串，但它很可能不包含合法的 UTF-8 编码字符序列。

I expect what you want is to convert the 16-byte static array of unsigned char into 32 ASCII hexadecimal characters [0-9a-f] using whatever algorithm you see fit.

我希望您想要的是使用您认为合适的任何算法将 16 字节的 unsigned char 静态数组转换为 32 个 ASCII 十六进制字符 [0-9a-f]。

回答by Rob Keniger

The MD5 function does not return a C string, it returns a pointer to some bytes. You can't treat it as a string.

MD5 函数不返回 C 字符串，它返回指向某些字节的指针。你不能把它当作一个字符串。

If you want to create a string, you need to build a string using the hex values of those bytes. Here is one way to do it as a category on NSData:

如果要创建字符串，则需要使用这些字节的十六进制值构建字符串。这是将其作为 NSData 类别的一种方法：

#import <CommonCrypto/CommonDigest.h>
@implementation NSData (MMAdditions)
- (NSString*)md5String
{
    unsigned char md5[CC_MD5_DIGEST_LENGTH];
    CC_MD5([self bytes], [self length], md5);
    return [NSString stringWithFormat: @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
            md5[0], md5[1],
            md5[2], md5[3],
            md5[4], md5[5],
            md5[6], md5[7],
            md5[8], md5[9],
            md5[10], md5[11],
            md5[12], md5[13],
            md5[14], md5[15]
            ];
}
@end

回答by nrj

@implementation NSString (MD5)

+ (NSString *)formattedMD5:(const char *)data length:(unsigned long)len
{
    unsigned char *digest = MD5((unsigned const char *)data, len, NULL);
    NSMutableArray *values = [[NSMutableArray alloc] init];

    for (int i = 0; i < strlen((char *)digest); i++)
    {
        char hexValue[4];
        sprintf(hexValue, "%02X", digest[i]);
        [values addObject:[NSString stringWithCString:hexValue length:strlen(hexValue)]];
    }

    // returns a formatted MD5 fingerprint like
    //      00:00:00:00:00:00:00:00:00
    return [values componentsJoinedByString:@":"];
}

@end

回答by virtplay

- (NSString*)MD5:(NSData *) data
    {
        // Create byte array of unsigned chars
        unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];

        // Create 16 byte MD5 hash value, store in buffer
        CC_MD5([data bytes], (CC_LONG)data.length, md5Buffer);

        // Convert unsigned char buffer to NSString of hex values
        NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
        for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x",md5Buffer[i]];

        return output;
    }

How to use

如何使用

NSString *yourStrToBeConverted;
NSData* data = [yourStrToBeConverted dataUsingEncoding:NSUTF8StringEncoding];
NSString *md5res=[self MD5:data];

回答by Gillsoft AB

These answers are correct but confusing. I post a working sample, since I had issues with most other answers. The code is tested and works well for Mac OS X 10.12.x and iOS 10.1.x.

这些答案是正确的，但令人困惑。我发布了一个工作样本，因为我对大多数其他答案都有疑问。该代码经过测试，适用于 Mac OS X 10.12.x 和 iOS 10.1.x。

YourClass.h

你的课堂.h

#import <CommonCrypto/CommonDigest.h>
@interface YourClass : NSObject
+ (NSString *) md5:(NSString *) input;
@end

YourClass.m

你的课堂.m

#import YourClass.h

+ (NSString *) md5:(NSString *) input
{
    const char *cStr = [input UTF8String];
    unsigned char digest[CC_MD5_DIGEST_LENGTH];
    CC_MD5(cStr, (uint32_t)strlen(cStr), digest);
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x", digest[i]]; //%02X for capital letters
    return output;
}

Usage (e.g. in some other class):

用法（例如在其他类中）：

SomeOtherClass.h

其他类.h

#import "YourClass.h"

SomeOtherClass.m

SomeOtherClass.m

-(void) Test
{
    //call by [self Test] or use somewhere in your code.
    NSString *password = @"mypassword123";
    NSString *md5 = [YourClass md5:password];
    NSLog(@"%@", password);
    NSLog(@"%@", md5);
}