I have a simple code using mbedtls to perform RSA decryption operations on an encrypted message. I’m trying to use multiple-thread to do the same operation concurrently. I’m interested in using stack memory instead of heap. mbedtls provides memory_buffer_alloc.h for stack-based memory allocator. Documentation of memory_buffer_alloc_init() says,
Initialize use of stack-based memory allocator.
The stack-based allocator does memory management inside the
presented buffer and does not call malloc() and free().
It sets the global polarssl_malloc() and polarssl_free() pointers
to its own functions.
(Provided polarssl_malloc() and polarssl_free() are thread-safe if
POLARSSL_THREADING_C is defined)
Therefore, I have added the following configuration into my config.h file,
#define POLARSSL_THREADING_PTHREAD
#define POLARSSL_THREADING_C
#define POLARSSL_MEMORY_C
#define POLARSSL_MEMORY_BUFFER_ALLOC_C
#define POLARSSL_PLATFORM_MEMORY
#define POLARSSL_PLATFORM_C
My code works for a single thread. However, when I increase the number of threads, my code shows error. Following is my source code,
#include "rsa/config.h"
#include "rsa/aes.h"
#include "rsa/bignum.h"
#include "rsa/rsa.h"
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/resource.h>
#include <pthread.h>
#include <time.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "rsa/key.h"
#include "rsa/memory_buffer_alloc.h"
#include "rsa/memory.h"
#include "rsa/platform.h"
#include "rsa/threading.h"
#define NUM_OF_THREAD 2
//threading_mutex_t lock;
void decryption(){
// initialize stack memory
unsigned char alloc_buf[10000];
memory_buffer_alloc_init( &alloc_buf, sizeof(alloc_buf) );
unsigned char private_encrypt[KEY_BUFFER_SIZE];
int total_dec=5;
unsigned char * buffer = 0;
long length;
unsigned char msg_decrypted[KEY_LEN];
// reading encrypted msg
FILE * fp2 = fopen ("msg.enc", "rb");
int size1=KEY_BUFFER_SIZE;
if(fp2){
while(size1>0){
fread(private_encrypt,1,sizeof (private_encrypt),fp2);
size1=size1-1;
}
}
fclose(fp2);
// reading rsa-private key
FILE * fp = fopen ("rsa_priv.txt", "rb");
if (fp){
fseek (fp, 0, SEEK_END);
length = ftell (fp);
fseek (fp, 0, SEEK_SET);
buffer = calloc (1,length+1);
if (buffer){
fread (buffer, 1, length, fp);
}
fclose (fp);
}
// initialize rsaContext
rsa_context rsaContext;
rsa_init(&rsaContext,RSA_PKCS_V15, 0);
rsaContext.len=KEY_LEN;
// spliting keys and load into rsa context
const char s[3] = "= ";
char *token;
int k=0, size;
char *rest=buffer;
// get the first token
token = strtok_r(rest,s,&rest);
// walk through other tokens
while( token != NULL ) {
size = strlen(token);
switch (k) {
case 1:
token[size-1]='\0';
mpi_read_string(&rsaContext.N, 16, token);
break;
case 3:
token[size-1]='\0';
mpi_read_string(&rsaContext.E, 16, token);
break;
case 5:
token[size-1]='\0';
mpi_read_string(&rsaContext.D, 16, token);
break;
case 7:
token[size-1]='\0';
mpi_read_string(&rsaContext.P, 16, token);
break;
case 9:
token[size-1]='\0';
mpi_read_string(&rsaContext.Q, 16, token);
break;
case 11:
token[size-1]='\0';
mpi_read_string(&rsaContext.DP, 16, token);
break;
case 13:
token[size-1]='\0';
mpi_read_string(&rsaContext.DQ, 16, token);
break;
case 15:
token[size-1]='\0';
mpi_read_string(&rsaContext.QP, 16, token);
break;
}
k=k+1;
token = strtok_r(rest, "= \n", &rest);
}
if( rsa_private(&rsaContext,private_encrypt, msg_decrypted) != 0 ) {
printf( "Decryption failed! %d\n", rsa_private(&rsaContext,private_encrypt, msg_decrypted));
}else{
printf("Decrypted plaintext-----> %s\n",msg_decrypted );
}
// free memory
memory_buffer_alloc_free();
}
void thread_function(void * input){
printf("Test thread\n");
int total_loop=5;
while(total_loop>0){
//pthread_mutex_lock(&lock); <-- multi-thread works with lock
decryption();
//pthread_mutex_unlock(&lock);
total_loop--;
}
}
int main(){
int i;
// total number of thread
pthread_t ths[NUM_OF_THREAD];
for (i = 0; i < NUM_OF_THREAD; i++) {
pthread_create(&ths[i], NULL, thread_function, NULL);
}
for (i = 0; i < NUM_OF_THREAD; i++) {
void* res;
pthread_join(ths[i], &res);
}
return 0;
}
If I use mutex, the above code works. I do not want to use a lock. It took a long time.
Can anyone please tell me what I’m doing wrong? How can I fix it?