preparations for use of multiple hash algos for challenge response

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

11 files changed, 134 insertions, 46 deletions

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 94ef12a..77484de 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -63,7 +63,7 @@ build-clang:
   script:
     - autoreconf -fi
     - CC=clang ./configure --enable-option-checking=fatal --prefix=/
-    - make install CFLAGS='-Werror -Wno-error=for-loop-analysis' DESTDIR="$(realpath ./deploy/clang)" V=s
+    - make install CFLAGS='-Werror' DESTDIR="$(realpath ./deploy/clang)" V=s
   stage: build
   artifacts:
     paths:
@@ -83,7 +83,7 @@ build-android:
     - cd ..
     - autoreconf -fi
     - CC=aarch64-linux-android28-clang PATH="${PATH}:$(realpath ./vendor/android-ndk-r19/toolchains/llvm/prebuilt/linux-x86_64/bin)" ./configure --enable-option-checking=fatal --host=aarch64-linux-android
-    - PATH="${PATH}:$(realpath ./vendor/android-ndk-r19/toolchains/llvm/prebuilt/linux-x86_64/bin)" make install CFLAGS='-Werror -Wno-error=for-loop-analysis' DESTDIR="$(realpath ./deploy/android28-clang)" V=s
+    - PATH="${PATH}:$(realpath ./vendor/android-ndk-r19/toolchains/llvm/prebuilt/linux-x86_64/bin)" make install CFLAGS='-Werror' DESTDIR="$(realpath ./deploy/android28-clang)" V=s
   stage: build
   artifacts:
     paths:
diff --git a/README b/README
index 6092f15..c11df67 100644
--- a/README
+++ b/README
@@ -123,7 +123,7 @@ installed.
 
 TODOs
 -----
-- challenge response: switch from md5 to sha-512
+- challenge response: switch from md5 to sha-512 (WiP)
 - packet obfuscation
 - encryption (metadata + payload)
 
diff --git a/README.md b/README.md
index 70ecb3f..5efc35c 100644
--- a/README.md
+++ b/README.md
@@ -141,7 +141,7 @@ installed.
 
 ## TODOs
 ```
-- challenge response: switch from md5 to sha-512
+- challenge response: switch from md5 to sha-512 (WiP)
 - packet obfuscation
 - encryption (metadata + payload)
 ```
diff --git a/src/challenge.c b/src/challenge.c
index f269313..f0b02ad 100644
--- a/src/challenge.c
+++ b/src/challenge.c
@@ -46,6 +46,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/time.h>
+#include <assert.h>
 
 #include "challenge.h"
 #include "options.h"
@@ -55,48 +56,66 @@
 /* generate_challenge: Generates a random challenge, incorporating the current
  * local timestamp to avoid replay attacks.
  */
-challenge_t* generate_challenge(void) {
+challenge_t *generate_challenge(void) {
 	struct timeval  tt;
 	challenge_t     *c;
 	int             i;
 
 	c = (challenge_t *) calloc(1, sizeof(challenge_t));
+    assert(c != NULL);
 	gettimeofday(&tt, 0);
-	c->sec      = tt.tv_sec;
-	c->usec_rnd = tt.tv_usec + pt_random();
+	c->plain.sec      = tt.tv_sec;
+	c->plain.usec_rnd = tt.tv_usec + pt_random();
 	for (i=0;i<6;i++)
-		c->random[i] = pt_random();
+		c->plain.random[i] = pt_random();
 
 	return c;
 }
 
-/* generate_response: Generates a response to the given challenge. The response
+/* generate_response_md5: Generates a response to the given challenge. The response
  * is generated by combining the concatenating the challenge data with the
  * md5 digest of the password, and then calculating the MD5 digest of the
  * entire buffer. The result is stored in the passed-in challenge, overwriting
  * the challenge data.
  */
-void generate_response(challenge_t *challenge) {
-	md5_byte_t  buf[sizeof(challenge_t)+kMD5_digest_size];
+void generate_response_md5(challenge_plain_t *plain, challenge_digest_t *digest) {
+	md5_byte_t  buf[sizeof(*plain) + kMD5_digest_size];
 	md5_state_t state;
 
-	memcpy(buf, challenge, sizeof(challenge_t));
-	memcpy(&buf[sizeof(challenge_t)], opts.password_digest, kMD5_digest_size);
-	memset(challenge, 0, sizeof(challenge_t));
+	digest->hash_type = HT_MD5;
+	memcpy(buf, plain, sizeof(*plain));
+	memcpy(&buf[sizeof(*plain)], opts.md5_password_digest, kMD5_digest_size);
+	memset(plain, 0, sizeof(*plain));
+
 	md5_init(&state);
-	md5_append(&state, buf, sizeof(challenge_t)+kMD5_digest_size);
-	md5_finish(&state, (md5_byte_t*)challenge);
+	md5_append(&state, buf, sizeof(*plain) + kMD5_digest_size);
+	md5_finish(&state, (md5_byte_t *) &digest->md5[0]);
 }
 
-/* validate_challenge: Checks whether a given response matches the expected
+/* validate_challenge_md5: Checks whether a given response matches the expected
  * response, returning 1 if validation succeeded, and 0 otherwise. Note that
  * overwriting the local challenge with the challenge result is not a problem,
  * as the data will not be used again anyway (authentication either succeeds,
  * or the connection is closed down).
  */
-int validate_challenge(challenge_t *local, challenge_t *remote) {
-	generate_response(local);
-	if (memcmp(local, remote, sizeof(challenge_t)) == 0)
+int validate_challenge_md5(challenge_t *local, challenge_digest_t *remote) {
+	generate_response_md5(&local->plain, &local->digest);
+	if (remote->hash_type == HT_MD5 &&
+	    memcmp(&local->digest.md5[0], &remote->md5[0], sizeof(local->digest.md5)) == 0)
+	{
 		return 1;
+	}
 	return 0;
 }
+
+#ifdef ENABLE_SHA512
+void generate_response_sha512(challenge_t *challenge)
+{
+    /* TODO: Implement me! */
+}
+
+int validate_challenge_sha512(challenge_t *local, challenge_t *remote)
+{
+	/* TODO: Implement me! */
+}
+#endif /* ENABLE_SHA512 */
diff --git a/src/challenge.h b/src/challenge.h
index 18495cf..203e420 100644
--- a/src/challenge.h
+++ b/src/challenge.h
@@ -46,23 +46,50 @@
 #ifndef CHALLENGE_H
 #define CHALLENGE_H 1
 
+#include "pconfig.h"
+
 #include <stdint.h>
+#ifdef ENABLE_SHA512
+#include <openssl/sha.h>
+#endif
 
-/** challenge_t: This structure contains the pseudo-random challenge used for
- * authentication.
- */
-typedef struct challenge_t {
+#define HT_MD5    0x1
+#define HT_SHA512 0x2
+
+
+typedef struct challenge_plain_t {
 	/** tv_sec as returned by gettimeofday */
 	uint32_t sec;
 	/** tv_usec as returned by gettimeofday + random value */
 	uint32_t usec_rnd;
 	/** random values */
 	uint32_t random[6];
+} __attribute__ ((packed)) challenge_plain_t;
+
+typedef struct challenge_digest_t {
+	uint8_t hash_type;
+	union {
+		unsigned char md5[kMD5_digest_size];
+		unsigned char sha512[kSHA512_digest_size];
+	};
+} __attribute__ ((packed)) challenge_digest_t;
+
+/** challenge_t: This structure contains the pseudo-random challenge used for
+ * authentication. If OpenSSL is available SHA512 will be used per default.
+ */
+typedef struct challenge_t {
+	challenge_plain_t plain;
+	challenge_digest_t digest;
 } __attribute__ ((packed)) challenge_t;
 
+challenge_t *generate_challenge(void);
+
+void generate_response_md5(challenge_plain_t *plain, challenge_digest_t *digest);
+int validate_challenge_md5(challenge_t *local, challenge_digest_t *remote);
 
-challenge_t* generate_challenge(void);
-void generate_response(challenge_t *challenge);
-int validate_challenge(challenge_t *local, challenge_t *remote);
+#ifdef ENABLE_SHA512
+void generate_response_sha512(challenge_plain_t *plain, challenge_digest_t *digest);
+int validate_challenge_sha512(challenge_t *local, challenge_digest_t *remote);
+#endif
 
 #endif
diff --git a/src/options.c b/src/options.c
index 79c11ec..10838ad 100644
--- a/src/options.c
+++ b/src/options.c
@@ -41,6 +41,9 @@
 #ifdef WIN32
 #include <ws2tcpip.h>
 #endif
+#ifdef ENABLE_SHA512
+#include <openssl/sha.h>
+#endif
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
@@ -169,6 +172,22 @@ static const struct option_usage usage[] = {
 		"Tune the number of empty pings to send with each explicit acknowledgement.\n"
 		"Empty pings can compensate for ICMP sequence number inspection.\n"
 	},
+	/** --force-md5 */
+	{"force-md5",    0, OPT_BOOL,   {.num = 0},
+		"Force MD5 as challenge response checksum generator.\n"
+#ifndef ENABLE_SHA512
+		"This is the default for this configuration.\n"
+#endif
+	},
+	/** --force-sha512 */
+	{"force-sha512", 0, OPT_BOOL,   {.num = 0},
+		"Force SHA512 as challenge response checksum generator.\n"
+#ifdef ENABLE_SHA512
+		"This is the default for this configuration.\n"
+#else
+		"SHA512 is not available for this configuration.\n"
+#endif
+	},
 	/** --daemon */
 	{"pidfile",      0, OPT_STR,    {.str = "/run/ptunnel.pid"},
 #ifdef WIN32
@@ -237,6 +256,8 @@ static struct option long_options[] = {
 	{"resend-interval", required_argument, 0, 't'},
 	{"payload-size", required_argument, 0, 'y'},
 	{"empty-pings", required_argument, 0, 'E'},
+	{"force-md5",         no_argument, &opts.force_md5, 1},
+	{"force-sha512",      no_argument, &opts.force_sha512, 1},
 	{"daemon",      optional_argument, 0, 'd'},
 	{"syslog",            no_argument, 0, 'S'},
 	{"user",        optional_argument, 0, 'u'},
@@ -498,13 +519,17 @@ int parse_options(int argc, char **argv) {
 				if (opts.password)
 					free(opts.password);
 				opts.password = strdup(optarg);
-				pt_log(kLog_debug, "Password set - unauthenicated connections will be refused.\n");
-				//  Compute the password digest
+				pt_log(kLog_debug, "%s\n", "Password set - unauthenicated connections will be refused.");
+				/* Compute the md5 password digest */
 				md5_init(&state);
 				md5_append(&state, (md5_byte_t*)optarg, strnlen(opts.password, BUFSIZ /* not optimal */));
-				md5_finish(&state, &opts.password_digest[0]);
+				md5_finish(&state, &opts.md5_password_digest[0]);
 				//  Hide the password in process listing
 				memset(optarg, '*', strnlen(optarg, BUFSIZ /* not optimal */));
+#ifdef ENABLE_SHA512
+				pt_log(kLog_debug, "%s\n", "Password set - sha512 authentication enabled.");
+				SHA512(optarg, strnlen(opts.password, BUFSIZ /* not optimal */), &opts.sha512_password_digest[0]);
+#endif
 				break;
 #ifndef WIN32
 			case 'd':
@@ -609,6 +634,16 @@ int parse_options(int argc, char **argv) {
 		exit(1);
 	}
 
+#if ENABLE_SHA512
+	if (opts.force_md5) {
+		pt_log(kLog_error, "%s\n", "You are forcing md5 but sha512 is available.");
+	}
+#else
+	if (opts.force_sha512) {
+		pt_log(kLog_error, "%s\n", "You are forcing sha512 but it isn't available.");
+	}
+#endif
+
 	if (opts.given_proxy_hostname) {
 		if ((ret = host_to_addr(opts.given_proxy_hostname, &opts.given_proxy_ip)) != 0) {
 			pt_log(kLog_error, "Failed to look up %s as destination address: %s\n",
diff --git a/src/options.h b/src/options.h
index 9c2ca3f..5551426 100644
--- a/src/options.h
+++ b/src/options.h
@@ -75,6 +75,10 @@ struct options {
 	/** Device to capture packets from */
 	char *pcap_device;
 #endif
+	/** Force MD5 based challenge response. */
+	int force_md5;
+	/** Force SHA512 based challenge response. */
+	int force_sha512;
 	/** List all available pcap devices and exit */
 	int list_pcap_devices;
 	/** Usually stdout, but can be altered by the user */
@@ -84,8 +88,10 @@ struct options {
 	int print_stats;
 	/** Password (must be the same on proxy and client for authentica  tion to succeed) */
 	char *password;
-	/** MD5 digest of challenge+password */
-	md5_byte_t password_digest[kMD5_digest_size];
+	/** MD5 digest of password */
+	md5_byte_t md5_password_digest[kMD5_digest_size];
+	/** SHA512 digest of password */
+	unsigned char sha512_password_digest[kSHA512_digest_size];
 	/** use UDP instead of ICMP */
 	int udp;
 	/** unpriviledged mode */
diff --git a/src/pconfig.h b/src/pconfig.h
index e13f7ee..5c642ee 100644
--- a/src/pconfig.h
+++ b/src/pconfig.h
@@ -88,6 +88,8 @@ enum {
 	kAutomatic_close_timeout = 60,   //  Seconds!
 	/** size of md5 digest in bytes */
 	kMD5_digest_size     = 16,
+	/** size of sha512 digest in bytes */
+	kSHA512_digest_size  = 64,
 	/** These constants are used to indicate the protocol state. The protocol
      * works as follows:
      * - The identifier is used by both the proxy and the forwarder
diff --git a/src/pkt.c b/src/pkt.c
index f1e134b..44af20d 100644
--- a/src/pkt.c
+++ b/src/pkt.c
@@ -236,7 +236,7 @@ void handle_packet(char *buf, unsigned bytes, int is_pcap, struct sockaddr_in *a
 							return;
 						}
 						pt_log(kLog_debug, "Got authentication challenge - sending response\n");
-						generate_response(challenge);
+						generate_response_md5(&challenge->plain, &challenge->digest);
 						queue_packet(icmp_sock, cur->pkt_type, (char*)challenge,
 						             sizeof(challenge_t), cur->id_no, cur->icmp_id,
 						             &cur->my_seq, cur->send_ring, &cur->send_idx,
@@ -254,8 +254,8 @@ void handle_packet(char *buf, unsigned bytes, int is_pcap, struct sockaddr_in *a
 					/* If proxy: Handle client's response to challenge */
 					else if (type_flag == proxy_flag) {
 						pt_log(kLog_debug, "Received remote challenge response.\n");
-						if (validate_challenge(cur->challenge, challenge) ||
-						                       cur->authenticated)
+						if (validate_challenge_md5(cur->challenge, &challenge->digest) ||
+						                           cur->authenticated)
 						{
 							pt_log(kLog_verbose, "Remote end authenticated successfully.\n");
 							handle_extended_options(cur);
@@ -438,8 +438,8 @@ void handle_extended_options(void *vcur)
 	if (cur->extended_options[0] > 0) {
 		if (cur->extended_options[0] > cur->window_size) {
 			size_t extend = cur->extended_options[0] - cur->window_size;
-			cur->send_ring = realloc(cur->send_ring, cur->extended_options[0] * sizeof(icmp_desc_t));
-			cur->recv_ring = realloc(cur->recv_ring, cur->extended_options[0] * sizeof(forward_desc_t *));
+			cur->send_ring = (icmp_desc_t *) realloc(cur->send_ring, cur->extended_options[0] * sizeof(icmp_desc_t));
+			cur->recv_ring = (forward_desc_t **) realloc(cur->recv_ring, cur->extended_options[0] * sizeof(forward_desc_t *));
 			memset(cur->send_ring + cur->window_size, 0, extend * sizeof(icmp_desc_t));
 			memset(cur->recv_ring + cur->window_size, 0, extend * sizeof(forward_desc_t *));
 		}
@@ -474,14 +474,14 @@ void handle_ack(uint16_t seq_no, icmp_desc_t ring[], int *packets_awaiting_ack,
 					pt_log(kLog_debug, "Received ack for only seq %d\n", seq_no);
 					pt_pkt	= (ping_tunnel_pkt_t*)ring[i].pkt->data;
 					/* WARNING: We make the dangerous assumption here that packets arrive in order! */
-					*remote_ack	= (uint16_t)ntohl(pt_pkt->ack);
+					*remote_ack	= (uint16_t) ntohl(pt_pkt->ack);
 					free(ring[i].pkt);
 					ring[i].pkt	= 0;
 					ring[i].pkt_len	= 0;
 					(*packets_awaiting_ack)--;
 					if (i == *first_ack) {
-						for (j=1;j<window_size;j++) {
-							k	= (i+j)%window_size;
+						for (j = 1; j < window_size; j += 2) {
+							k	= (i + j) % window_size;
 							if (ring[k].pkt) {
 								*first_ack = k;
 								break;
@@ -489,7 +489,6 @@ void handle_ack(uint16_t seq_no, icmp_desc_t ring[], int *packets_awaiting_ack,
 							/* we have looped through everything */
 							if (k == i)
 								*first_ack = insert_idx;
-							j++;
 						}
 					}
 					return;
@@ -525,7 +524,6 @@ void handle_ack(uint16_t seq_no, icmp_desc_t ring[], int *packets_awaiting_ack,
 			}
 		}
 	}
-/* else
- * 	pt_log(kLog_verbose, "Dropping superfluous acknowledgement (no outstanding packets needing ack.)\n");
- */
+	else
+		pt_log(kLog_verbose, "Dropping superfluous acknowledgement (no outstanding packets needing ack.)\n");
 }
diff --git a/src/ptunnel.c b/src/ptunnel.c
index bdf0a6f..c63c57a 100644
--- a/src/ptunnel.c
+++ b/src/ptunnel.c
@@ -175,7 +175,8 @@ int main(int argc, char *argv[]) {
 		return -1;
 #endif
 
-	memset(opts.password_digest, 0, kMD5_digest_size);
+	memset(opts.md5_password_digest, 0, kMD5_digest_size);
+	memset(opts.sha512_password_digest, 0, kSHA512_digest_size);
 
 	/* The seq_expiry_tbl is used to prevent the remote ends from prematurely
 	 * re-using a sequence number.
diff --git a/src/utils.c b/src/utils.c
index a65f947..8e340d4 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -160,7 +160,7 @@ int pt_random(void) {
 #ifdef HAVE_ARC4RANDOM
 	return arc4random();
 #else
-#if defined(USE_CUSTOMRNG) && !defined(_WIN32)
+#if defined(RNGDEV) && !defined(_WIN32)
 	static int rng_fd = -1;
 	ssize_t bytes_read;
 	int rnd_val;