MD5()函数在哪个库中? [英] In which library is the MD5() function?

问题描述

当我在编写要在目标计算机上安装的代码时，我想知道依赖项，并注意到不需要openssl库.我纳闷，因为我知道我正在使用OpenSSL:

As I'm writing code to install on a target machine, I was wondering about the dependencies and noticed that there were no openssl library needed. I wondered because I know I am using OpenSSL:

#include <openssl/md5.h>

...
MD5(a, b, c);
...

令我惊讶的是，似乎我们只针对libc被链接了. MD5确实是在libc中实现的，而不是在某些libssl库中实现的吗?

To my surprise, it seems that we only get linked against libc. Is MD5 really implemented in libc and not in some libssl library?

objdump给我有关链接库的信息:

objdump gives me the info about the linked library:

Dynamic Section:
  NEEDED               libQtCore.so.4
  NEEDED               libstdc++.so.6
  NEEDED               libgcc_s.so.1
  NEEDED               libc.so.6
  SONAME               libcontent.so

---

正如noloader所建议的那样，我尝试了ldd，但仍然看不到对MD5有意义的库. libcontent.so直接使用MD5()...

---

As suggested by noloader I tried with ldd and still fail to see a library that would make sense for MD5. libcontent.so is directly using MD5()...

ldd ../BUILD/snapwebsites/plugins/content/libcontent.so 
    linux-vdso.so.1 =>  (0x00007fff4f3ff000)
    libQtCore.so.4 => /usr/lib/x86_64-linux-gnu/libQtCore.so.4 (0x00007ff37ad0f000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007ff37aa0c000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007ff37a7f5000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ff37a42c000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007ff37a20f000)
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007ff379ff7000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007ff379df3000)
    libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007ff379af7000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007ff3798ee000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007ff3795e9000)
    /lib64/ld-linux-x86-64.so.2 (0x00007ff37b5e5000)
    libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007ff3793a9000)

---

此外，为了确保这一点，我在该内容库上尝试了nm，然后可以看到MD5条目:

---

Also, just to make sure, I tried nm on that content library and I can see the MD5 entry:

                 w _ITM_registerTMCloneTable
00000000003c9468 d __JCR_END__
00000000003c9468 d __JCR_LIST__
                 w _Jv_RegisterClasses
                 U MD5                       <---- it's here...
                 U memcmp@@GLIBC_2.2.5
                 w pthread_cancel
                 U pthread_mutex_destroy@@GLIBC_2.2.5

推荐答案

MD5()函数在哪个库中?

In which library is the MD5() function?

OpenSSL库.链接到libcrypto.参见 md5(3).

The OpenSSL library. Link to libcrypto. See md5(3).

MD5是否真的在libc中实现，而不是在某些libssl库中实现?

Is MD5 really implemented in libc and not in some libssl library?

好吧，它不在Ubuntu的libc中:

Well, its not in Ubuntu's libc:

$ nm -D  /lib/x86_64-linux-gnu/libc.so.6 | grep -i md5
$

它在OpenSSL的libcrypto中:

And it is in OpenSSL's libcrypto:

$ nm -D /usr/lib/x86_64-linux-gnu/libcrypto.so | grep MD5
0000000000066840 T MD5
0000000000066640 T MD5_Final
0000000000066790 T MD5_Init
0000000000066630 T MD5_Transform
0000000000066420 T MD5_Update

T表示符号(MD5)在TEXT部分中定义并导出. t表示该符号在TEXT部分中定义，但未导出，因此您无法链接该符号(请考虑GCC的visibility=private或静态声明).

The T means the symbol (MD5) is defined in the TEXT section and its exported. A t means the symbol is defined in the TEXT section, but its not exported so you cannot link against it (think GCC's visibility=private or a static declaration).

如果得到U，则表示该符号是必需的，但未定义，并且必须提供一个库.

If you get a U, then that means the symbol is required but undefined and a library will have to provide it.

#include <openssl/md5.h>

...
MD5(a, b, c, d);

MD5(a, b, c, d);不是OpenSSL的MD5. OpenSSL的MD5具有三个参数，而不是四个.

MD5(a, b, c, d); is not OpenSSL's MD5. OpenSSL's MD5 has three parameters, not four.

objdump给我有关链接库的信息

objdump gives me the info about the linked library

ldd可能会给您不同的结果.它是我用来检查依赖项的(并且我不使用objdump):

ldd might give you different results. Its what I use to check dependencies (and I don't use objdump):

$ cat t.c
#include <openssl/md5.h>

int main(int argc, char* argv[])
{
    const char password[] = "password";
    char hash[MD5_DIGEST_LENGTH];    
    MD5(password, sizeof(password), hash);

    return 0;
}

$ gcc t.c -o t.exe -lcrypto
$ ldd t.exe 
    linux-vdso.so.1 =>  (0x00007fff435ff000)
    libcrypto.so.1.0.0 => /usr/lib/x86_64-linux-gnu/libcrypto.so.1.0.0 (0x00007fbaff01b000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fbafec90000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fbafea8b000)
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fbafe874000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fbaff429000)

和t.exe的未解析符号:

$ nm t.exe | grep MD5
    U MD5@@OPENSSL_1.0.0

这篇关于MD5()函数在哪个库中?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！