"no OPENSSL_Applink " in OpenSSL3.0.5

[Matt Caswell]

On 10/08/2022 00:11, Imazu Setsuo wrote:
> Hello, my name is Imazu.
> I am using OpenSSL3.0.5 to develop a windows program.
> When I call PEM_read_PrivateKey() I get the following error:
> OPENSSL_Uplink(00007FF8011DD3E0,08): no OPENSSL_Applink
> 
> The source that calls PEM_read_PrivateKey() includes the following sources.
> 
> #include <openssl/applink.c>
> 
> In the test program
> test.exe --> my_appl.dll --> openssl.dll
> , the above include is the source in my_appl.dll.
> The depends tool (Dependency Walker) can check the entry of 
> OPENSSL_Applink.
> 
> By the way, if you describe "#include <openssl/applink.c>" in the source 
> inside test.exe, it will work.
> However, I want to complete the processing within my_appl.dll.
> Please tell me a good way.
> 
> Best regards.
> 

The problem comes when your code opens a FILE* and then passes it for 
use to OpenSSL. If your code and OpenSSL are using a different C runtime 
then that's going to fail.

A possible workaround is not call PEM_read_PrivateKey() at all and 
instead use PEM_read_bio_PrivateKey(). You can then (for example) load 
the file into memory completely within your code and store the data in a 
mem BIO (e.g. using BIO_new_mem_buf()). This removes the need to pass 
FILE * pointers from one dll to another and avoids the problem.

Matt