utils: Add random buffer generation function

Define and export the u_randbuf() function that fills a buffer with
random data.
Convert L2TP's challenge generation code for using it.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>

3 files changed, 40 insertions, 18 deletions

diff --git a/accel-pppd/ctrl/l2tp/l2tp.c b/accel-pppd/ctrl/l2tp/l2tp.c
index 267a47f..c6ba82f 100644
--- a/accel-pppd/ctrl/l2tp/l2tp.c
+++ b/accel-pppd/ctrl/l2tp/l2tp.c
@@ -223,8 +223,7 @@ static int l2tp_tunnel_genchall(uint16_t chall_len,
 				struct l2tp_packet_t *pack)
 {
 	void *ptr = NULL;
-	size_t urandlen;
-	ssize_t rdlen;
+	int err;
 
 	if (chall_len == 0
 	    || conf_secret == NULL || conf_secret_len == 0) {
@@ -248,26 +247,18 @@ static int l2tp_tunnel_genchall(uint16_t chall_len,
 		conn->challenge_len = chall_len;
 	}
 
-	for (urandlen = 0; urandlen < chall_len; urandlen += rdlen) {
-		rdlen = read(urandom_fd, conn->challenge + urandlen,
-			     chall_len - urandlen);
-		if (rdlen < 0) {
-			if (errno == EINTR)
-				rdlen = 0;
-			else {
-				log_tunnel(log_error, conn,
-					   "impossible to generate Challenge:"
-					   " reading from urandom failed: %s\n",
-					   strerror(errno));
-				goto err;
-			}
-		} else if (rdlen == 0) {
+	if (u_randbuf(conn->challenge, chall_len, &err) < 0) {
+		if (err)
+			log_tunnel(log_error, conn,
+				   "impossible to generate Challenge:"
+				   " reading from urandom failed: %s\n",
+				   strerror(err));
+		else
 			log_tunnel(log_error, conn,
 				   "impossible to generate Challenge:"
 				   " end of file reached while reading"
 				   " from urandom\n");
-			goto err;
-		}
+		goto err;
 	}
 
 	if (l2tp_packet_add_octets(pack, Challenge, conn->challenge,
diff --git a/accel-pppd/utils.c b/accel-pppd/utils.c
index a6a76c9..45e8709 100644
--- a/accel-pppd/utils.c
+++ b/accel-pppd/utils.c
@@ -1,12 +1,15 @@
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include "triton.h"
 #include "utils.h"
 
 #include "memdebug.h"
 
+extern int urandom_fd;
+
 void __export u_inet_ntoa(in_addr_t addr, char *str)
 {
 	sprintf(str, "%i.%i.%i.%i", addr & 0xff, (addr >> 8) & 0xff, (addr >> 16) & 0xff, (addr >> 24) & 0xff);
@@ -30,3 +33,30 @@ int __export u_readlong(long int *dst, const char *src,
                 return 0;
         }
 }
+
+int __export u_randbuf(void *buf, size_t buf_len, int *err)
+{
+	uint8_t *u8buf = buf;
+	ssize_t rd_len;
+
+	while (buf_len) {
+		rd_len = read(urandom_fd, u8buf, buf_len);
+		if (rd_len < 0) {
+			if (errno == EINTR)
+				rd_len = 0;
+			else {
+				if (err)
+					*err = errno;
+				return -1;
+			}
+		} else if (rd_len == 0) {
+			if (err)
+				*err = 0;
+			return -1;
+		}
+		u8buf += rd_len;
+		buf_len -= rd_len;
+	}
+
+	return 0;
+}
diff --git a/accel-pppd/utils.h b/accel-pppd/utils.h
index bb1a00a..be62f6a 100644
--- a/accel-pppd/utils.h
+++ b/accel-pppd/utils.h
@@ -5,5 +5,6 @@
 
 void u_inet_ntoa(in_addr_t, char *str);
 int u_readlong(long int *dst, const char *src, long int min, long int max);
+int u_randbuf(void *buf, size_t buf_len, int *err);
 
 #endif