Question

I am trying to implement OpenSSL RSA, following 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);
    BIO *bio_out = NULL;
    FILE *fp;

    if (!ctx)
    {
        perror("Error in CTX \n");
    }
    if (EVP_PKEY_keygen_init(ctx) <= 0)
    {
        perror("Error in EVP_PKEY_keygen_init \n");
    }
    if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 2048) <= 0)
    {
        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");
    if ((bio_out = BIO_new_fp(fp, BIO_NOCLOSE)) == NULL)
    {
        perror("Error in new BIO \n");
    }

    BIO_set_flags(bio_out, BIO_FLAGS_WRITE);
    EVP_PKEY_print_private(bio_out,pkey,5, NULL);

    fclose(fp);
    BIO_free(bio_out);

    fp = fopen(PUBFILE, "w");
    if ((bio_out = BIO_new_fp(fp, BIO_NOCLOSE)) == NULL)
    {
        perror("Error in new BIO \n");
    }

    BIO_set_flags(bio_out, BIO_FLAGS_WRITE);
    EVP_PKEY_print_public(bio_out,pkey,5, NULL);

    fclose(fp);
    BIO_free(bio_out);

    return 0;
}

And here is the pub.pem:

 Public-Key: (2048 bit)
 Modulus:
     00:be:bc:04:74:39:5b:31:2d:76:bf:41:9a:3e:6e:
     d0:cf:8f:c3:25:86:6b:38:ff:58:96:fc:bb:2b:d9:
     af:df:fa:bf:aa:1e:c7:58:1d:2b:ce:6c:90:0f:d3:
     30:b7:90:fc:1c:7c:84:f3:31:80:3e:04:ad:bd:74:
     dc:92:60:01:9e:40:82:31:b3:8d:a5:ac:fb:81:83:
     c5:e9:e6:56:0b:f4:df:dd:f3:e4:7f:3b:b6:85:d7:
     c9:41:08:3f:bf:15:bd:6d:19:ff:13:fc:4a:52:59:
     93:77:b0:be:78:01:da:db:b2:7d:f9:38:98:e0:d2:
     45:79:3c:60:0d:a1:65:74:d2:9c:9b:7c:15:2c:e4:
     ee:eb:76:52:f3:61:95:8b:d6:fb:5e:fb:f7:c6:40:
     70:77:86:fb:60:87:07:f3:58:49:74:d6:0a:cf:d4:
     70:09:50:73:20:1e:4e:52:4c:59:34:a0:f5:7a:80:
     57:e5:8a:8c:d1:a1:94:a4:ab:75:99:fd:55:62:06:
     34:dd:83:00:aa:3f:c8:0a:a1:0e:80:1a:ba:42:6e:
     23:37:eb:bd:1f:e4:a2:c4:fa:2a:84:84:e4:dc:ec:
     a2:a5:36:2c:c6:cb:28:81:8c:89:15:64:f4:ef:ec:
     1e:c8:c3:d5:c2:02:54:ce:bb:72:20:b4:4a:05:2f:
     dc:75
 Exponent: 65537 (0x10001)

Following is the code which I am using for encryption:

#include <stdio.h> 
#include <stdlib.h> 

#include <openssl/evp.h> 
#include <openssl/pem.h> 
#include <openssl/rsa.h> 
#include <openssl/err.h> 

#include <arpa/inet.h> /* For htonl() */ 

int do_evp_seal(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]; 

    if (!PEM_read_RSA_PUBKEY(rsa_pkey_file, &rsa_pkey, NULL, NULL)) 
    { 
        fprintf(stderr, "Error loading RSA Public Key File.\n"); 
        // here I am getting this error:
        // 140121481717416:error:0906D06C:lib(9):func(109):reason(108):pem_lib.c:696:Expecting: PUBLIC KEY

        ERR_print_errors_fp(stderr); 
        retval = 2; 
        goto out; 
    }

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

    if (!EVP_SealInit(&ctx, EVP_aes_128_cbc(), &ek, &eklen, iv, &pkey, 1)) 
    { 
        fprintf(stderr, "EVP_SealInit: failed.\n"); 
        retval = 3; 
        goto out_free; 
    } 

    /* First we write out the encrypted key length, then the encrypted key, 
     * then the iv (the IV length is fixed by the cipher we have chosen). 
     */ 

    eklen_n = htonl(eklen); 
    if (fwrite(&eklen_n, sizeof eklen_n, 1, out_file) != 1) 
    { 
        perror("output file"); 
        retval = 5; 
        goto out_free; 
    } 
    if (fwrite(ek, eklen, 1, out_file) != 1) 
    { 
        perror("output file"); 
        retval = 5; 
        goto out_free; 
    } 
    if (fwrite(iv, EVP_CIPHER_iv_length(EVP_aes_128_cbc()), 1, out_file) != 1) 
    { 
        perror("output file"); 
        retval = 5; 
        goto out_free; 
    } 

    /* Now we process the input file and write the encrypted data to the 
     * output file. */ 

    while ((len = fread(buffer, 1, sizeof buffer, in_file)) > 0) 
    { 
        if (!EVP_SealUpdate(&ctx, buffer_out, &len_out, buffer, len)) 
        { 
            fprintf(stderr, "EVP_SealUpdate: 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_SealFinal(&ctx, buffer_out, &len_out)) 
    { 
        fprintf(stderr, "EVP_SealFinal: 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; 
} 

int main(int argc, char *argv[]) 
{ 
    FILE *rsa_pkey_file; 
    int rv; 

    rsa_pkey_file = fopen("pub.pem", "rb"); 
    if (!rsa_pkey_file) 
    { 
        fprintf(stderr, "Error loading PEM RSA Public Key File.\n"); 
        exit(2); 
    } 

    rv = do_evp_seal(rsa_pkey_file, stdin, stdout); 

    fclose(rsa_pkey_file); 
    return rv; 
}

Why is PEM_read_RSA_PUBKEY returning ERROR: Expecting PUBLIC KEY?

Answer 1

OK, I found out myself I have write PEM_write_bio_PUBKEY(bio_out,pkey ); instead of EVP_PKEY_print_public(bio_out,pkey)