How to add openssl lib in android studio with experimental gradle plugin (NDK)?

Question

I'm trying to add openSSL library to my project in android studio 2.0 preview 7 with experimental gradle plugin.

dependencies {
    classpath 'com.android.tools.build:gradle-experimental:0.4.0'
}

What I did is that I downloaded the openSSL library and put it into jni folder. And I have another .c file that uses this library. I have included the files that I need and there are no errors in code. My .c file name is hello-jni.c and I declared it into my build.gradle (module: app) like this:

android.ndk {
    moduleName = "hello-jni"
}

and also I loaded my library in my MainActivity like this:

static {
    System.loadLibrary("hello-jni");
}

but when I try to build my project, an error shows up like this:

Error:(51) undefined reference to `RSA_generate_key'
Error:error: ld returned 1 exit status
Error:Execution failed for task ':app:linkArm64-v8aDebugHello-    jniSharedLibrary'.
> A build operation failed.
  Linker failed while linking libhello-jni.so.

My hello-jni.c source code:

#include <jni.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include "boringssl/crypto/openssl/base.h"
#include "boringssl/crypto/openssl/rsa.h"
#include "boringssl/crypto/openssl/pem.h"

#define KEY_LENGTH  2048
#define PUB_EXP     3
#define PRINT_KEYS
#define WRITE_TO_FILE 0

size_t pri_len;            // Length of private key
size_t pub_len;            // Length of public key
char   *pri_key;           // Private key
char   *pub_key;           // Public key
char   msg[KEY_LENGTH/8];  // Message to encrypt
char   *encrypt = NULL;    // Encrypted message
char   *decrypt = NULL;    // Decrypted message
char   *err;               // Buffer for any error messages

JNIEXPORT jstring JNICALL
Java_com_example_ndktest_SignUpActivity_testString(JNIEnv *env, jobject activity) {

// In this line, the error happens!(in build time)
RSA *keypair = RSA_generate_key(KEY_LENGTH, PUB_EXP, NULL, NULL);

//continue to work with key pair ...

return "some jstring";
}

Answer 1

You need to specify the openssl library as a dependency. There's a snippet here showing how to add a prebuilt library.