如何使用openssl中的BIO从pem文件读取公钥？

Question

我正在使用openssl库，我想用BIO从. pem文件中读取公钥。我尝试了这个，但我的rsa变量仍然未初始化：

 RSA *rsa = RSA_new();

 BIO *keybio = NULL;

 keybio = BIO_new(BIO_s_file());
 BIO_read_filename(keybio, "public.pem");

 // and also tried this instead of last two lines:
 // keybio = BIO_new_file("public.rem", "r");

 rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa, NULL, NULL);

当我调试应用程序时，它向我显示如下内容：

rsa { padding = ???, n = ??? , ...} 
rsa->n <unable to read from memory> and so on for all rsa fields.

我的文件有效，密钥是按照PKCS#1格式生成的。我用asn1解析器解析了它。

Answer 1

你的代码看起来很好。尝试以下输入：

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1IHYYTavz9PQRxpcyO7J
m0dtiIjNUvW3coLQQKhq+wySTTN1cwm2zYTw0FSfLDPOtOBNXFwKF9wykiyHS2uU
D8vIU+T/fvlcADYTtZqdC5AoBWlSuhp0xqqtHmNUEjGa4FpRmKusL8s5/cuAfNRV
NVSxA3JCN3kYrT9Q1qBN+XbOQn+h7gPQU3ICmG7L1R/CwIsq/wwUbq+NeY0TMvz5
LM6AIS+GCV0UeJVm6UN6GDBCOHk02XuplyhkbCsNhq+HTfhHVeE1s7NcIavmgvqm
EtlIcTGemW9tXs5/REZUv+SDpR6RLUKhwuij/Ft5Pe9b7cH3wXqNmOBhJ3F/ht2C
swIDAQAB
-----END PUBLIC KEY-----

将其与您在asn1解析器中看到的内容进行比较：

$ openssl asn1parse -in public.pem
    0:d=0  hl=4 l= 290 cons: SEQUENCE          
    4:d=1  hl=2 l=  13 cons: SEQUENCE          
    6:d=2  hl=2 l=   9 prim: OBJECT            :rsaEncryption
   17:d=2  hl=2 l=   0 prim: NULL              
   19:d=1  hl=4 l= 271 prim: BIT STRING