openssl用于验证签名的C语言代码示例

以下是使用 OpenSSL 库进行签名验证的示例代码。假设您已经有了签名和公钥证书的文件。

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

int main() {
    // 读取签名文件
    FILE* f = fopen("signature.bin", "rb");
    if (!f) {
        perror("Failed to open signature file");
        return EXIT_FAILURE;
    }
    fseek(f, 0, SEEK_END);
    long siglen = ftell(f);
    rewind(f);
    unsigned char* sig = (unsigned char*)malloc(siglen);
    fread(sig, 1, siglen, f);
    fclose(f);

    // 读取公钥文件
    BIO* bio = BIO_new_file("public.crt", "r");
    if (!bio) {
        perror("Failed to open public key file");
        return EXIT_FAILURE;
    }
    X509* cert = PEM_read_bio_X509(bio, NULL, NULL, NULL);
    EVP_PKEY* pubkey = X509_get_pubkey(cert);

    // 读取要验证的文件
    f = fopen("file_to_verify.bin", "rb");
    if (!f) {
        perror("Failed to open file to verify");
        return EXIT_FAILURE;
    }
    fseek(f, 0, SEEK_END);
    long datalen = ftell(f);
    rewind(f);
    unsigned char* data = (unsigned char*)malloc(datalen);
    fread(data, 1, datalen, f);
    fclose(f);

    // 创建签名上下文并验证签名
    EVP_MD_CTX* mdctx = EVP_MD_CTX_new();
    EVP_VerifyInit(mdctx, EVP_sha256());
    EVP_VerifyUpdate(mdctx, data, datalen);
    int result = EVP_VerifyFinal(mdctx, sig, siglen, pubkey);

    // 清理资源
    EVP_MD_CTX_free(mdctx);
    EVP_PKEY_free(pubkey);
    X509_free(cert);
    BIO_free(bio);
    free(sig);
    free(data);

    // 输出验证结果
    if (result == 1) {
        printf("Signature verification succeeded!\n");
        return EXIT_SUCCESS;
    }
    else if (result == 0) {
        printf("Signature verification failed!\n");
        return EXIT_FAILURE;
    }
    else {
        printf("Error occurred during signature verification!\n");
        return EXIT_FAILURE;
    }
}

这是一个简单的示例，您需要根据自己的需求进行修改和扩展。