Getting error in EVP_OpenInit() of OpenSSL EVP api

I am facing a problem in RSA decryption using OpenSSL Library (EVP api). Here is my code for key generation

#include <stdio.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/bio.h>
#include <openssl/pem.h>

#define SECFILE "sec.pem"
#define PUBFILE "pub.pem"

int main()
{

    EVP_PKEY_CTX *ctx;
    EVP_PKEY *pkey = NULL;
    ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL);
    FILE *fp;

    if (!ctx)
    {
        /* Error occurred */
        perror("Error in CTX \n");

    }
    if (EVP_PKEY_keygen_init(ctx) <= 0)
    {
        /* Error */
        perror("Error in EVP_PKEY_keygen_init \n");
    }
    if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 2048) <= 0)
    {
        /* Error */
        perror("Error in EVP_PKEY_CTX_set_rsa_keygen_bits \n");
    }
    /* Generate key */
    if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
    {   
        /* Error */
        perror("Error in EVP_PKEY_keygen \n");

    }


    fp = fopen(SECFILE, "w");
    PEM_write_PrivateKey(fp, pkey, NULL,NULL, 0,0, NULL);
    fclose(fp);

    fp = fopen(PUBFILE, "w");
    PEM_write_PUBKEY(fp,pkey);
    fclose(fp);


    return 0;
}

For encryption :

I used this link

For decryption :

   int do_evp_open(FILE *rsa_pkey_file, FILE *in_file, FILE *out_file) 
{ 
    int retval = 0; 
    RSA *rsa_pkey = NULL; 
    EVP_PKEY *pkey = EVP_PKEY_new(); 
    EVP_CIPHER_CTX ctx; 
    unsigned char buffer[4096]; 
    unsigned char buffer_out[4096 + EVP_MAX_IV_LENGTH]; 
    size_t len; 
    int len_out; 
    unsigned char *ek; 
    int eklen ; 
    uint32_t eklen_n; 
    unsigned char iv[EVP_MAX_IV_LENGTH] = {122,205,106,192,4,183,69,176,84,28,214,226,220,140,86,174}; 


    /// Read RSA Private Key 
    if (PEM_read_RSAPrivateKey(rsa_pkey_file, &rsa_pkey, NULL, NULL) == NULL) 
    { 
        fprintf(stderr, "Error loading RSA Private Key File.\n"); 
        ERR_print_errors_fp(stderr); 
        retval = -2; 
        goto out; 
    } 


    /// Assign RSA key to EVP key
    if (!EVP_PKEY_assign_RSA(pkey, rsa_pkey)) 
    { 
        fprintf(stderr, "EVP_PKEY_assign_RSA: failed.\n"); 
        retval = -3; 
        goto out; 
    }

    EVP_CIPHER_CTX_init(&ctx); 

    ek = malloc( EVP_PKEY_size(pkey)); 



    if (!EVP_OpenInit(&ctx, EVP_aes_128_cbc(), ek, eklen, iv,pkey)) 
    { 
        fprintf(stderr, "EVP_OpenInit: failed.\n"); 
       ERR_print_errors_fp(stderr); /// Prints error of occured in Openssl  
        retval = -3; 
        goto out_free; 
    } 




    while ((len = fread(buffer, 1, sizeof buffer, in_file)) > 0) 
    { 
        if (!EVP_OpenUpdate(&ctx, buffer_out, &len_out, buffer, len)) 
        { 
            fprintf(stderr, "EVP_OpenUpdate: failed.\n"); 
            retval = 3; 
            goto out_free; 
        } 

        if (fwrite(buffer_out, len_out, 1, out_file) != 1) 
        { 
            perror("output file"); 
            retval = -5; 
            goto out_free; 
        } 
    } 

    if (ferror(in_file)) 
    { 
        perror("input file"); 
        retval = -4; 
        goto out_free; 
    } 

    if (!EVP_OpenFinal(&ctx, buffer_out, &len_out)) 
    { 
        fprintf(stderr, "EVP_OpenFinal: failed.\n"); 
        retval = - 3; 
        goto out_free; 
    } 

    if (fwrite(buffer_out, len_out, 1, out_file) != 1) 
    { 
        perror("output file"); 
        retval = -5; 
        goto out_free; 
    } 

    out_free: 
    EVP_PKEY_free(pkey); 
    free(ek); 

    out: 
    return retval; 
}

My Private and public keys are :

The error I am getting While EVP_OpenInit is :

140004942804648:error:0407106B:lib(4):func(113):reason(107):rsa_pk1.c:190: 140004942804648:error:04065072:lib(4):func(101):reason(114):rsa_eay.c:594

Any help would be appreciated. Thanks, Pawan

回答1:

Are you absolutely sure, that you have initialized variable eklen?

回答2:

I see you have used EVP_OpenInit(), EVP_OpenUpdate() and EVP_OpenFinal() for decryption. So I'm going to assume that you've used EVP_SealInit(), EVP_SealUpdate() and EVP_SealFinal() functions for encryption.

So if you have used EVP_SealInit(), you must have passed the address (pointer) to eklen (please check man EVP_SealInit) where the variable gets a value assigned. In analogous to that the eklen variable that you are passing to EVP_OpenInit() must contain a valid key length.

The following is the description from man EVP_OpenInit.

EVP_OpenInit() initializes a cipher context ctx for decryption with cipher type. It decrypts the encrypted symmetric key of length ekl bytes passed in the ek parameter using the private key priv. The IV is supplied in the iv parameter.

I'm not sure here, but I guess you need to use EVP_PKEY_size() function in this case to get the length of the key.

For example (in your decryption code):

....
..
. 
EVP_CIPHER_CTX_init(&ctx); 
ek = malloc( EVP_PKEY_size(pkey)); 

/* Add the following line */
eklen = EVP_PKEY_size(pkey);

if (!EVP_OpenInit(&ctx, EVP_aes_128_cbc(), ek, eklen, iv,pkey)) 
{ 
    fprintf(stderr, "EVP_OpenInit: failed.\n"); 
...
..
.