我正在研究一个内核模块，该模块使用内核crypto api的非对称密码，内核版本为4.8.0。我通过openssl生成非对称密钥对，将它们转换为DER格式（我知道它是BER的一个子集），并将代码编入我的模块。私钥工作得很好，但是公钥在crypto_akcipher_set_pub_key中总是失败，即使我尝试了更多其他密钥对。 dmesg只是打印：
[16891.604718] next_op: pc=0/10 dp=0/161 C=0 J=0
[16891.604721] - match? 30 30 00
[16891.604724] - TAG: 30 158 CONS
[16891.604726] next_op: pc=2/10 dp=3/161 C=1 J=0
[16891.604727] - match? 30 02 32
[16891.604729]
ASN1: Unexpected tag [m=2 d=4 ot=02 t=30 l=158]
[16891.604730] set key error! -74,,,,,0
以下是我的问题：
A）dmesg是否意味着公钥错误？如何生成内核加密密钥对？
B）我找不到内核非对称密码的可用rsa密钥对，即使在Linux/crypto/testmgr.h或libkcapi/test/test.sh也没有，你能帮助我吗？
谢谢！
这是我的模块：
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <linux/gfp.h>
#include <linux/err.h>
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <crypto/skcipher.h>
#include <crypto/akcipher.h>
#include <linux/random.h>
#include <linux/delay.h>
#include <linux/highmem.h>
const char *priv_key =
"\x30\x82\x02\x5d\x02\x01\x00\x02\x81\x81\x00\xd0"
"\xb4\x5a\xc1\x9e\x2e\x4d\xae\xbd\x51\x39\xcc\x4b"
"\x12\xf5\x76\x30\xcf\x39\x97\xf1\xd3\x0d\xaa\x37"
"\x70\x2d\x2f\x01\xc9\x69\x09\xe3\x4e\xd5\x90\x68"
"\xfe\xbf\x7c\x8b\x86\xdf\xf3\x14\xb3\x96\xcf\x1b"
"\x39\xe3\xe6\x8a\x77\x6d\xe4\x89\xef\xdb\xba\x4a"
"\x40\x6d\xa9\xec\x21\x62\x00\xa4\xc3\x45\xcc\xdd"
"\x56\xb2\x77\x59\x46\x17\x27\x0e\x2c\xfe\x85\x53"
"\x72\x26\x9b\xdc\x24\x83\xd1\x67\xa7\x4c\x88\x70"
"\x78\x3f\x1c\x60\xd4\x95\x14\x57\xfc\xdb\x15\xaa"
"\xab\x31\x32\xb2\x44\x72\xdd\xb0\x0b\x13\x62\x03"
"\x50\x1d\xd4\x6a\xf6\xb2\x23\x02\x03\x01\x00\x01"
"\x02\x81\x80\x7b\x83\x10\xe6\xde\xf7\x26\x30\x10"
"\x88\x3e\x7d\x61\xbc\xa1\x99\xc5\xbf\x0d\xa5\x97"
"\x8e\xc0\xda\x88\x9e\x91\x8e\xed\x2e\xc6\x43\xfc"
"\xcb\x0d\xe6\xbd\xcc\x6d\x84\x86\x8a\x56\x84\xe4"
"\x2e\x78\x44\xaf\x27\x2e\x71\xa4\x66\x93\x99\x99"
"\xec\x62\x8c\x38\x1f\x33\x06\x37\xc1\x9d\x17\x6b"
"\xad\xfb\x8e\x44\xd3\x11\xcb\x74\xa4\x01\x78\xb0"
"\x9c\x64\xd3\x0d\x63\x99\x65\xe3\xca\xae\x11\xb2"
"\xc4\x00\x36\xc2\xfc\x4b\x7b\x6f\x9e\x84\xb6\x97"
"\x00\x56\x5b\x09\xa1\x28\xf5\x28\x8d\xc7\x93\x45"
"\xba\xc0\x6b\xa9\x2d\xeb\x02\xcd\xde\x1e\x29\x02"
"\x41\x00\xf6\x0e\x41\xbc\xfa\x40\x82\xba\xa0\x6a"
"\xa5\x75\x5c\xcd\xfe\xa8\x11\xa6\xef\xbc\xad\x5f"
"\x86\x40\xb4\x5a\x65\xc1\x7b\x5e\x89\xc2\x60\x38"
"\x0e\x8b\x7d\x7d\x99\x30\x01\xf1\xea\x1e\x3e\x46"
"\xf4\xd2\xd9\x80\xaf\x3a\x4b\x2f\xbb\x91\xbb\xb7"
"\x22\x2d\x6a\x0f\x4e\x6f\x02\x41\x00\xd9\x23\xa7"
"\x98\x0c\x58\xe1\x5d\xa7\x15\x05\xc6\xd9\x7b\xc5"
"\x7b\xd3\x01\x8b\x1e\xf1\x2e\x99\xc5\xac\x41\xf1"
"\x92\x88\xd9\x8e\x50\x86\xf9\x2f\x66\x42\xeb\xf9"
"\x80\x78\xfa\xc7\xea\x63\x35\x7e\x6f\xc5\x35\x36"
"\x6b\xa1\x8a\xa3\x49\x97\xbc\xa6\x9b\x5c\x6e\xf1"
"\x8d\x02\x40\x44\x70\xa0\xbe\x64\xc9\x4e\xd3\x84"
"\x4d\x45\xaa\x88\x5e\xcf\xe7\x85\xc9\x6e\x43\x87"
"\xe1\xdb\x20\xe2\x49\x86\xa6\x33\x9f\x8f\x27\xde"
"\xc5\x98\xde\x19\xd0\xb6\xac\x50\xce\x2e\x35\xad"
"\x52\xe5\x44\x44\xb5\x73\x87\xfe\x63\xcf\x83\x70"
"\xb8\x36\xac\x75\x24\xbe\xc7\x02\x41\x00\x87\xd2"
"\x97\xa8\xb2\x40\x7e\x67\xf8\x75\x5b\xf1\xb0\x64"
"\x8d\x79\x10\xd9\xec\x4d\xe4\x8b\x43\xc0\xb4\x29"
"\x63\x94\x47\x69\xde\x6d\x5c\xa0\x4e\x17\xe7\x50"
"\x77\xf6\xf6\xb5\xd7\x8b\x33\x97\x68\x89\x3d\x90"
"\x35\x84\x49\xbd\xd0\xb9\xdd\xe2\x31\x4d\x09\x1a"
"\x94\x99\x02\x41\x00\xc9\x12\xec\x64\xe9\x01\x27"
"\x10\x6c\xad\xc5\x83\x8a\x26\x39\xe0\x05\xde\xde"
"\xf9\x1a\x5d\xf6\xcb\xe8\xd2\x9b\x40\xd5\x11\xc8"
"\x9a\x6d\x29\xb6\x15\x36\x9a\xee\x45\xe2\x51\x14"
"\xa8\x2d\xab\x57\x86\x80\x87\x0a\x02\xaf\xfa\xda"
"\x5e\x7d\xfb\x84\xd1\x3a\xe0\xed\x57";
const int priv_key_len = 609;
const char *pub_key =
"\x30\x81\x9e\x30\x0d\x06\x09\x2a\x86\x48\x86\xf7"
"\x0d\x01\x01\x01\x05\x00\x03\x81\x8c\x00\x30\x81"
"\x88\x02\x81\x80\x6d\x4d\xaf\xf5\x32\x98\xfa\x33"
"\xf2\x4a\xb0\x50\x27\x6f\x50\x0b\x28\xca\x5f\x6e"
"\xde\xec\x7b\xae\xeb\xd1\x89\xdf\xcf\x8d\x12\x6c"
"\x0d\xf2\x32\x65\xb7\x04\xf2\xb8\x76\x67\xe9\x28"
"\xc3\x12\x6b\x4a\x52\x09\xd6\x61\x9b\x21\x25\x04"
"\xe0\x9a\xec\xbc\x25\x3f\xfc\x6f\x1a\x98\xa8\x02"
"\xa8\x2e\x89\x91\x20\xcf\xf0\xd1\x9d\x09\x35\xac"
"\x95\xe2\xe4\x8e\x5b\x7c\x34\x93\x39\x4f\x33\xbd"
"\x6e\xe7\xc5\xbb\x2a\x28\x32\x13\x62\x39\x37\x87"
"\x40\xe7\x59\xf8\x94\xad\xc4\x2e\xaf\x23\xf4\x98"
"\xcd\x90\x27\x96\x41\xc6\x4a\xcd\x6d\x56\xfd\x5b"
"\x02\x03\x01\x00\x01";
const int pub_key_len = 161;
const char *msg = "\x54\x85\x9b\x34\x2c\x49\xea\x2a";
const int msg_len = 8;
char *crypted = NULL;
int crypted_len = 0;
struct tcrypt_result {
struct completion completion;
int err;
};
struct akcipher_testvec {
unsigned char *key;
unsigned char *msg;
unsigned int key_size;
unsigned int msg_size;
};
static inline void hexdump(unsigned char *buf,unsigned int len) {
while(len--)
printk("%02x",*buf++);
printk("\n");
}
static void tcrypt_complete(struct crypto_async_request *req, int err)
{
struct tcrypt_result *res = req->data;
if (err == -EINPROGRESS)
return;
res->err = err;
complete(&res->completion);
}
static int wait_async_op(struct tcrypt_result *tr, int ret)
{
if (ret == -EINPROGRESS || ret == -EBUSY) {
wait_for_completion(&tr->completion);
reinit_completion(&tr->completion);
ret = tr->err;
}
return ret;
}
static int uf_akcrypto(struct crypto_akcipher *tfm,
void *data, int datalen, int phase)
{
void *xbuf = NULL;
struct akcipher_request *req;
void *outbuf = NULL;
struct tcrypt_result result;
unsigned int out_len_max = 0;
struct scatterlist src, dst;
int err = -ENOMEM;
xbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!xbuf)
return err;
req = akcipher_request_alloc(tfm, GFP_KERNEL);
if (!req)
goto free_xbuf;
init_completion(&result.completion);
if (!phase) //test
err = crypto_akcipher_set_pub_key(tfm, pub_key, pub_key_len);
else
err = crypto_akcipher_set_priv_key(tfm, priv_key, priv_key_len);
// err = crypto_akcipher_set_priv_key(tfm, priv_key, priv_key_len);
if (err){
printk("set key error! %d,,,,,%d\n", err,phase);
goto free_req;
}
err = -ENOMEM;
out_len_max = crypto_akcipher_maxsize(tfm);
outbuf = kzalloc(out_len_max, GFP_KERNEL);
if (!outbuf)
goto free_req;
if (WARN_ON(datalen > PAGE_SIZE))
goto free_all;
memcpy(xbuf, data, datalen);
sg_init_one(&src, xbuf, datalen);
sg_init_one(&dst, outbuf, out_len_max);
akcipher_request_set_crypt(req, &src, &dst, datalen, out_len_max);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
tcrypt_complete, &result);
if (phase){
err = wait_async_op(&result, crypto_akcipher_encrypt(req));
if (err) {
pr_err("alg: akcipher: encrypt test failed. err %d\n", err);
goto free_all;
}
memcpy(crypted,outbuf,out_len_max);
crypted_len = out_len_max;
hexdump(crypted, out_len_max);
}else{
err = wait_async_op(&result, crypto_akcipher_decrypt(req));
if (err) {
pr_err("alg: akcipher: decrypt test failed. err %d\n", err);
goto free_all;
}
hexdump(outbuf, out_len_max);
}
free_all:
kfree(outbuf);
free_req:
akcipher_request_free(req);
free_xbuf:
kfree(xbuf);
return err;
}
static int userfaultfd_akcrypto(void *data, int datalen, int phase)
{
struct crypto_akcipher *tfm;
int err = 0;
tfm = crypto_alloc_akcipher("rsa", CRYPTO_ALG_INTERNAL, 0);
if (IS_ERR(tfm)) {
pr_err("alg: akcipher: Failed to load tfm for rsa: %ld\n", PTR_ERR(tfm));
return PTR_ERR(tfm);
}
err = uf_akcrypto(tfm,data,datalen,phase);
crypto_free_akcipher(tfm);
return err;
}
static int __init test_init(void)
{
crypted = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!crypted){
printk("crypted kmalloc error\n");
return -1;
}
userfaultfd_akcrypto(msg,msg_len,1);
userfaultfd_akcrypto(crypted,crypted_len,0);
kfree(crypted);
}
static void __exit test_exit(void)
{
}
module_init(test_init);
module_exit(test_exit);
MODULE_LICENSE("GPL");
答案 0 :(得分：1)
我自己已经弄明白了。
事实是openssl生成的公钥是正确的，但它包含更多信息，而内核crypto api并不需要这些信息。使用额外的数据，内核ctypto api无法正确解析公钥结构，这就是为什么＆＃34; ASN1：意外标记＆＃34;。
查看内核兼容的公钥here，它只包含 以下要素：
{
total size
integer size and value
integer size and value
}
以下命令将显示openssl生成的公共密钥的结构：
openssl asn1parse -in public_key.der -inform DER
输出如下：
0:d=0 hl=3 l= 159 cons: SEQUENCE
3:d=1 hl=2 l= 13 cons: SEQUENCE
5:d=2 hl=2 l= 9 prim: OBJECT :rsaEncryption
16:d=2 hl=2 l= 0 prim: NULL
18:d=1 hl=3 l= 141 prim: BIT STRING
真实数据位于BIT STRING中。它的偏移量是18.所以从偏移18到结束是你想要的数据。
您可以通过输入以下命令来读取BIT STRING内部结构：
openssl asn1parse -in public_key.der -inform DER -strparse 18
输出如：
0:d=0 hl=3 l= 137 cons: SEQUENCE
3:d=1 hl=3 l= 129 prim: INTEGER :D0B45AC19E2E4DA ....
135:d=1 hl=2 l= 3 prim: INTEGER :010001
与内核兼容的公钥结构相同。
答案 1 :(得分：1)
实际上，偏移量18 + 4中的数据是在Ubuntu18.04（Linux内核5.3）上对我们来说“ crypto_akcipher_set_pub_key”所需的公钥。因为从偏移量18开始的前4个字节是用于记录asn1结构体的长度和类型的头信息，其后是asn1结构体的实际内容，而仅从18 + 4开始的BIT STRING的内容才是内核兼容的公钥。 试试这个命令。 “ -offset”选项要求openssl从某个偏移量到末尾解析原始文件的内容，而“ -strparse”选项要求openssl在某个偏移量下解析asn1结构的内容。
openssl asn1parse -in publickey.der inform der -offset 18
输出为：
0:d=1 hl=3 l= 141 prim: BIT STRING
如果将偏移量更改为22，则输出为：
0:d=0 hl=3 l= 137 cons: SEQUENCE
3:d=1 hl=3 l= 129 prim: INTEGER :BA23E5D...
135:d=1 hl=2 l= 3 prim: INTEGER :010001
这意味着偏移量22中的数据就是我们想要的。