implemented MSCHAP-v2 authentication protocol

1 files changed, 446 insertions, 0 deletions

diff --git a/accel-pptpd/auth_mschap_v2.c b/accel-pptpd/auth_mschap_v2.c
new file mode 100644
index 0000000..3b6bd13
--- /dev/null
+++ b/accel-pptpd/auth_mschap_v2.c
@@ -0,0 +1,446 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+#include <byteswap.h>
+#include <arpa/inet.h>
+
+#include <openssl/md4.h>
+#include <openssl/des.h>
+#include <openssl/sha.h>
+
+#include "log.h"
+#include "ppp.h"
+#include "ppp_auth.h"
+#include "ppp_lcp.h"
+#include "pwdb.h"
+
+#define CHAP_CHALLENGE 1
+#define CHAP_RESPONSE  2
+#define CHAP_SUCCESS   3
+#define CHAP_FAILURE   4
+
+#define VALUE_SIZE 16
+#define RESPONSE_VALUE_SIZE (16+8+24+1)
+
+#define MSG_FAILURE   "E=691 R=0 C=cccccccccccccccccccccccccccccccc V=3 M=Authentication failure"
+#define MSG_SUCCESS   "S=cccccccccccccccccccccccccccccccccccccccc M=Authentication successed"
+
+#define HDR_LEN (sizeof(struct chap_hdr_t)-2)
+
+static int urandom_fd;
+static uint8_t magic1[39] =
+         {0x4D, 0x61, 0x67, 0x69, 0x63, 0x20, 0x73, 0x65, 0x72, 0x76,
+          0x65, 0x72, 0x20, 0x74, 0x6F, 0x20, 0x63, 0x6C, 0x69, 0x65,
+          0x6E, 0x74, 0x20, 0x73, 0x69, 0x67, 0x6E, 0x69, 0x6E, 0x67,
+          0x20, 0x63, 0x6F, 0x6E, 0x73, 0x74, 0x61, 0x6E, 0x74};
+static uint8_t magic2[41] =
+         {0x50, 0x61, 0x64, 0x20, 0x74, 0x6F, 0x20, 0x6D, 0x61, 0x6B,
+          0x65, 0x20, 0x69, 0x74, 0x20, 0x64, 0x6F, 0x20, 0x6D, 0x6F,
+          0x72, 0x65, 0x20, 0x74, 0x68, 0x61, 0x6E, 0x20, 0x6F, 0x6E,
+          0x65, 0x20, 0x69, 0x74, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6F,
+          0x6E};
+
+struct chap_hdr_t
+{
+	uint16_t proto;
+	uint8_t code;
+	uint8_t id;
+	uint16_t len;
+} __attribute__((packed));
+
+struct chap_challenge_t
+{
+	struct chap_hdr_t hdr;
+	uint8_t val_size;
+	uint8_t val[VALUE_SIZE];
+	char name[0];
+} __attribute__((packed));
+
+struct chap_response_t
+{
+	struct chap_hdr_t hdr;
+	uint8_t val_size;
+	uint8_t peer_challenge[16];
+	uint8_t reserved[8];
+	uint8_t nt_hash[24];
+	uint8_t flags;
+	char name[0];
+} __attribute__((packed));
+
+struct chap_failure_t
+{
+	struct chap_hdr_t hdr;
+	char message[sizeof(MSG_FAILURE)];
+} __attribute__((packed));
+
+struct chap_success_t
+{
+	struct chap_hdr_t hdr;
+	char message[sizeof(MSG_SUCCESS)];
+} __attribute__((packed));
+
+
+struct chap_auth_data_t
+{
+	struct auth_data_t auth;
+	struct ppp_handler_t h;
+	struct ppp_t *ppp;
+	int id;
+	uint8_t val[VALUE_SIZE];
+};
+
+static void chap_send_challenge(struct chap_auth_data_t *ad);
+static void chap_recv(struct ppp_handler_t *h);
+static int chap_check_response(struct chap_auth_data_t *ad, struct chap_response_t *res);
+
+static void print_buf(const uint8_t *buf,int size)
+{
+	int i;
+	for(i=0;i<size;i++)
+		log_debug("%x",buf[i]);
+}
+static void print_str(const char *buf,int size)
+{
+	int i;
+	for(i=0;i<size;i++)
+		log_debug("%c",buf[i]);
+}
+
+
+
+static struct auth_data_t* auth_data_init(struct ppp_t *ppp)
+{
+	struct chap_auth_data_t *d=malloc(sizeof(*d));
+
+	memset(d,0,sizeof(*d));
+	d->auth.proto=PPP_CHAP;
+	d->ppp=ppp;
+
+	return &d->auth;
+}
+
+static void auth_data_free(struct ppp_t *ppp,struct auth_data_t *auth)
+{
+	struct chap_auth_data_t *d=container_of(auth,typeof(*d),auth);
+
+	free(d);
+}
+
+static int chap_start(struct ppp_t *ppp, struct auth_data_t *auth)
+{
+	struct chap_auth_data_t *d=container_of(auth,typeof(*d),auth);
+
+	d->h.proto=PPP_CHAP;
+	d->h.recv=chap_recv;
+
+	ppp_register_chan_handler(ppp,&d->h);
+
+	chap_send_challenge(d);
+
+	return 0;
+}
+
+static int chap_finish(struct ppp_t *ppp, struct auth_data_t *auth)
+{
+	struct chap_auth_data_t *d=container_of(auth,typeof(*d),auth);
+
+	ppp_unregister_handler(ppp,&d->h);
+
+	return 0;
+}
+
+static int lcp_send_conf_req(struct ppp_t *ppp, struct auth_data_t *d, uint8_t *ptr)
+{
+	*ptr=0x81;
+	return 1;
+}
+
+static int lcp_recv_conf_req(struct ppp_t *ppp, struct auth_data_t *d, uint8_t *ptr)
+{
+	if (*ptr==0x81)
+		return LCP_OPT_ACK;
+	return LCP_OPT_NAK;
+}
+
+static void chap_send_failure(struct chap_auth_data_t *ad)
+{
+	struct chap_failure_t msg=
+	{
+		.hdr.proto=htons(PPP_CHAP),
+		.hdr.code=CHAP_FAILURE,
+		.hdr.id=ad->id,
+		.hdr.len=htons(sizeof(msg)-1-2),
+		.message=MSG_FAILURE,
+	};
+	
+	log_debug("send [MSCHAP-v2 Failure id=%x \"%s\"]\n",msg.hdr.id,MSG_FAILURE);
+
+	ppp_chan_send(ad->ppp,&msg,ntohs(msg.hdr.len)+2);
+}
+
+static int generate_response(struct chap_auth_data_t *ad, struct chap_response_t *msg, uint8_t *response)
+{
+	MD4_CTX md4_ctx;
+	SHA_CTX sha_ctx;
+	char *passwd;
+	char *u_passwd;
+	char *name;
+	uint8_t pw_hash[MD4_DIGEST_LENGTH];
+	uint8_t c_hash[SHA_DIGEST_LENGTH];
+	int i;
+	
+	name=strndup(msg->name,ntohs(msg->hdr.len)-sizeof(*msg)+2);
+	passwd=pwdb_get_passwd(ad->ppp,name);
+	if (!passwd)
+	{
+		free(name);
+		return -1;
+	}
+
+	u_passwd=malloc(strlen(passwd)*2);
+	for(i=0; i<strlen(passwd); i++)
+	{
+		u_passwd[i*2]=passwd[i];
+		u_passwd[i*2+1]=0;
+	}
+
+	MD4_Init(&md4_ctx);
+	MD4_Update(&md4_ctx,u_passwd,strlen(passwd)*2);
+	MD4_Final(pw_hash,&md4_ctx);
+
+	MD4_Init(&md4_ctx);
+	MD4_Update(&md4_ctx,pw_hash,16);
+	MD4_Final(pw_hash,&md4_ctx);
+
+	SHA1_Init(&sha_ctx);
+	SHA1_Update(&sha_ctx,pw_hash,16);
+	SHA1_Update(&sha_ctx,msg->nt_hash,24);
+	SHA1_Update(&sha_ctx,magic1,39);
+	SHA1_Final(response,&sha_ctx);
+
+	SHA1_Init(&sha_ctx);
+	SHA1_Update(&sha_ctx,msg->peer_challenge,16);
+	SHA1_Update(&sha_ctx,ad->val,16);
+	SHA1_Update(&sha_ctx,name,strlen(name));
+	SHA1_Final(c_hash,&sha_ctx);
+
+	SHA1_Init(&sha_ctx);
+	SHA1_Update(&sha_ctx,response,20);
+	SHA1_Update(&sha_ctx,c_hash,8);
+	SHA1_Update(&sha_ctx,magic2,41);
+	SHA1_Final(response,&sha_ctx);
+	
+	free(name);
+	free(passwd);
+	free(u_passwd);
+
+	return 0;
+}
+
+static void chap_send_success(struct chap_auth_data_t *ad, struct chap_response_t *res_msg)
+{
+	struct chap_success_t msg=
+	{
+		.hdr.proto=htons(PPP_CHAP),
+		.hdr.code=CHAP_SUCCESS,
+		.hdr.id=ad->id,
+		.hdr.len=htons(sizeof(msg)-1-2),
+		.message=MSG_SUCCESS,
+	};
+	uint8_t response[20];
+	int i;
+
+	if (generate_response(ad,res_msg,response))
+		return;
+	for(i=0; i<20; i++)
+		sprintf(msg.message+2+i*2,"%02X",response[i]);
+	msg.message[2+i*2]=' ';
+	
+	log_debug("send [MSCHAP-v2 Success id=%x \"%s\"]\n",msg.hdr.id,msg.message);
+
+	ppp_chan_send(ad->ppp,&msg,ntohs(msg.hdr.len)+2);
+}
+
+static void chap_send_challenge(struct chap_auth_data_t *ad)
+{
+	struct chap_challenge_t msg=
+	{
+		.hdr.proto=htons(PPP_CHAP),
+		.hdr.code=CHAP_CHALLENGE,
+		.hdr.id=++ad->id,
+		.hdr.len=htons(sizeof(msg)-2),
+		.val_size=VALUE_SIZE,
+	};
+
+	read(urandom_fd,ad->val,VALUE_SIZE);
+	memcpy(msg.val,ad->val,VALUE_SIZE);
+
+	log_debug("send [MSCHAP-v2 Challenge id=%x <",msg.hdr.id);
+	print_buf(msg.val,VALUE_SIZE);
+	log_debug(">]\n");
+
+	ppp_chan_send(ad->ppp,&msg,ntohs(msg.hdr.len)+2);
+}
+
+static void chap_recv_response(struct chap_auth_data_t *ad, struct chap_hdr_t *hdr)
+{
+	struct chap_response_t *msg=(struct chap_response_t*)hdr;
+
+	log_debug("recv [MSCHAP-v2 Response id=%x <", msg->hdr.id);
+	print_buf(msg->peer_challenge,16);
+	log_debug(">, <");
+	print_buf(msg->nt_hash,24);
+	log_debug(">, F=%i, name=\"",msg->flags);
+	print_str(msg->name,ntohs(msg->hdr.len)-sizeof(*msg)+2);
+	log_debug("\"]\n");
+
+	if (msg->hdr.id!=ad->id)
+	{
+		log_error("mschap-v2: id mismatch\n");
+		chap_send_failure(ad);
+		ppp_terminate(ad->ppp);
+	}
+
+	if (msg->val_size!=RESPONSE_VALUE_SIZE)
+	{
+		log_error("mschap-v2: value-size should be %i, expected %i\n",RESPONSE_VALUE_SIZE,msg->val_size);
+		chap_send_failure(ad);
+		ppp_terminate(ad->ppp);
+	}
+
+	if (chap_check_response(ad,msg))
+	{
+		chap_send_failure(ad);
+		auth_failed(ad->ppp);
+	}else
+	{
+		chap_send_success(ad,msg);
+		auth_successed(ad->ppp);
+	}
+}
+
+static void des_encrypt(const uint8_t *input, const uint8_t *key, uint8_t *output)
+{
+	int i,j,parity;
+	union
+	{
+		uint64_t u64;
+		uint8_t buf[8];
+	} p_key;
+	DES_cblock cb;
+	DES_cblock res;
+	DES_key_schedule ks;
+
+	memcpy(p_key.buf,key,7);
+	p_key.u64=bswap_64(p_key.u64);
+
+	for(i=0;i<8;i++)
+	{
+		cb[i]=(((p_key.u64<<(7*i))>>56)&0xfe);
+		for(j=0, parity=0; j<7; j++)
+			if ((cb[i]>>(j+1))&1) parity++;
+		cb[i]|=(~parity)&1;
+	}
+
+	DES_set_key_checked(&cb, &ks);
+	memcpy(cb,input,8);
+	DES_ecb_encrypt(&cb,&res,&ks,DES_ENCRYPT);
+	memcpy(output,res,8);	
+}
+
+static int chap_check_response(struct chap_auth_data_t *ad, struct chap_response_t *msg)
+{
+	MD4_CTX md4_ctx;
+	SHA_CTX sha_ctx;
+	uint8_t z_hash[21];
+	uint8_t c_hash[SHA_DIGEST_LENGTH];
+	uint8_t nt_hash[24];
+	char *passwd;
+	char *u_passwd;
+	char *name;
+	int i;
+	
+	name=strndup(msg->name,ntohs(msg->hdr.len)-sizeof(*msg)+2);
+	passwd=pwdb_get_passwd(ad->ppp,name);
+	if (!passwd)
+	{
+		free(name);
+		log_debug("mschap-v2: user not found\n");
+		chap_send_failure(ad);
+		return -1;
+	}
+
+	u_passwd=malloc(strlen(passwd)*2);
+	for(i=0; i<strlen(passwd); i++)
+	{
+		u_passwd[i*2]=passwd[i];
+		u_passwd[i*2+1]=0;
+	}
+
+	SHA1_Init(&sha_ctx);
+	SHA1_Update(&sha_ctx,msg->peer_challenge,16);
+	SHA1_Update(&sha_ctx,ad->val,16);
+	SHA1_Update(&sha_ctx,name,strlen(name));
+	SHA1_Final(c_hash,&sha_ctx);
+
+	memset(z_hash,0,sizeof(z_hash));
+	MD4_Init(&md4_ctx);
+	MD4_Update(&md4_ctx,u_passwd,strlen(passwd)*2);
+	MD4_Final(z_hash,&md4_ctx);
+
+	des_encrypt(c_hash,z_hash,nt_hash);
+	des_encrypt(c_hash,z_hash+7,nt_hash+8);
+	des_encrypt(c_hash,z_hash+14,nt_hash+16);
+
+	free(name);
+	free(passwd);
+	free(u_passwd);
+
+	return memcmp(nt_hash,msg->nt_hash,24);
+}
+
+static struct ppp_auth_handler_t chap=
+{
+	.name="MSCHAP-v2",
+	.init=auth_data_init,
+	.free=auth_data_free,
+	.send_conf_req=lcp_send_conf_req,
+	.recv_conf_req=lcp_recv_conf_req,
+	.start=chap_start,
+	.finish=chap_finish,
+};
+
+static void chap_recv(struct ppp_handler_t *h)
+{
+	struct chap_auth_data_t *d=container_of(h,typeof(*d),h);
+	struct chap_hdr_t *hdr=(struct chap_hdr_t *)d->ppp->chan_buf;
+
+	if (d->ppp->chan_buf_size<sizeof(*hdr) || ntohs(hdr->len)<HDR_LEN || ntohs(hdr->len)<d->ppp->chan_buf_size-2)
+	{
+		log_warn("mschap-v2: short packet received\n");
+		return;
+	}
+
+	if (hdr->code==CHAP_RESPONSE) chap_recv_response(d,hdr);
+	else
+	{
+		log_warn("mschap-v2: unknown code received %x\n",hdr->code);
+	}
+}
+
+static void __init auth_mschap_v2_init()
+{
+	urandom_fd=open("/dev/urandom",O_RDONLY);
+	if (urandom_fd<0)
+	{
+		log_error("mschap-v2: failed to open /dev/urandom: %s\n",strerror(errno));
+		return;
+	}
+	if (ppp_auth_register_handler(&chap))
+		log_error("mschap-v2: failed to register handler\n");
+}
+