将 RSA 公钥从字符串传递到 RSA * 结构时出错

Question

I try to load a public RSA key to my program. I use openssl lib in C. The key is defined in header crypt.h file:

#define PUBLIC_KEY  "-----BEGIN PUBLIC KEY-----\n" \
                    "MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAuDcT2OiToi9edqil/3ha\n" \
                    "1MMrgqYvdYObRkb8C5SZtf8iv4LynuHi3hvEtybqFW84Uf2l3Dxuz3IWVp2v1C2f\n" \
                    "cUxwf+hFqL4Nt2Ww/XOKLtFXTSX/2fPYoelmLja2grHPSuFx6N4gtDUXRIGSYXIz\n" \
                    "c2GBx8lOiOP+qUguFmWZ9E0GiMLvh4XUQUzTGr4ZNNoc5LODdO0g7beFFqhntt9w\n" \
                    "EKdceGQtA7Zyt5l13x0lj+RONdPJkDFZrNGdqDwNUSog9mufpvR1P2UW09pC+lzy\n" \
                    "z32P+w0U3Za4zv4Btis9ky16vaqdN/KlDWJRt+4W9TQSAL0x9w708OQr0Sf2CXNq\n" \
                    "EobSLZ/aybe75yQmzFqmn10X+NuwTtJkArIKK7JONCBSxjohQmTZw0U497TCEHia\n" \
                    "itzgsHNLf1of31G/3GK5rCkm9fl39nnrg0yJi1cONTDjSHzKlrPhA584jFRD0CIO\n" \
                    "VNHYgsVLuFQuJ0WkZON8uEZELXN1ZyWnmPXH8wSwxjud65JD4JSQornCXorBMfxd\n" \
                    "DFEeeNk8tjgPMaCTLFNP/gfVDzkvcct9RoC8uZxHk8zgrGOwuxOZ/ZyihE7M8v0i\n" \
                    "+VwG9iMrPl8W3+KqunIt/FB4Le1vJ0yYorK64DRNdeMAIsYq2iFWO3GXNsX631/K\n" \
                    "EuZJS8tGNhK9dF5umo0GceUCAwEAAQ==\n" \
                    "-----END PUBLIC KEY-----\n"

The RSA key is supposed to be saved in RSA * structure. I use a global variable for that.

RSA *rsaPubkey;

The main() calls a function that will take PUBLIC_KEY and pass it to rsaPubkey . The function is shown bellow:

#include "crypt.h"

int EVP_PKEY_get_type(EVP_PKEY *pkey) {
    if (!pkey)
        return EVP_PKEY_NONE;

    return EVP_PKEY_type(pkey->type);
}

int PublicRSAKeyToStruct(const char *pubKey) {
    BIO* bio;
    bio = BIO_new_mem_buf(pubKey, (int)sizeof(pubKey));
    if (bio == NULL) {
        printf("bio");
        return -1;
    }

    EVP_PKEY* pkey;
    PEM_read_bio_PUBKEY(bio, &pkey, NULL, NULL);
    if (pkey == NULL) {
        printf("pkey");
        return -1;
    }

    int type = EVP_PKEY_get_type(pkey);
    if (type != EVP_PKEY_RSA && type != EVP_PKEY_RSA2) {
        printf("get type");
        return -1;
    }

    rsaPubkey = EVP_PKEY_get1_RSA(pkey);
    if (rsaPubkey == NULL) {
        printf("pubkey");
        return -1;
    }

    EVP_PKEY_free(pkey);
    BIO_free(bio);
    return 0;
}

We call the function like that:

status = PublicRSAKeyToStruct(PUBLIC_KEY);
if (status == -1) {
    exit(EXIT_FAILURE);
}

My problem is that the PublicRSAKeyToStruct() function throws me the bellow user defined error:

get type

This means that we failed to pass EVP_PKEY_get_type() . I can't understand why this happen though. I have also no clue if the problem is on the previous steps.

Answer 1

Your PEM_read call failed because the BIO you gave it doesn't access the correct data, but you didn't check the return value, and you didn't initialize pkey so even though it's not valid your pkey == NULL check doesn't catch it. As described in the man page on your system (unless Windows) or on the web the second argument to BIO_new_mem_buf must either be the number of bytes in the buffer or -1 if buffer contains a null-terminated C string -- and a string literal like yours does yield a null-terminated string so -1 is suitable -- but sizeof(apointer) is neither of these.

The remainder of your code is correct and works fine if you give it a valid EVP_PKEY* .