Adds ice-pwd and ice-ufrag to sdp answer

Adds simple base64 encoder as pwd and ufrag are expected to be
base64 encoded. Uses prng to generate random data. Is this secure?

4 files changed, 115 insertions, 2 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 5855857..beeb2b3 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,7 +1,7 @@
 lib_LTLIBRARIES = liburtc.la
-liburtc_la_SOURCES = g711.c g711_tables.c mdns.c prng.c sdp.c urtc.c \
+liburtc_la_SOURCES = b64.c g711.c g711_tables.c mdns.c prng.c sdp.c urtc.c \
 						uuid.c
-include_HEADERS = err.h g711.h mdns.h prng.h sdp.h urtc.h uuid.h
+include_HEADERS = urtc.h
 
 # for pthreads support on linux
 liburtc_la_CFLAGS  = $(PTHREAD_CFLAGS)
diff --git a/src/b64.c b/src/b64.c
new file mode 100644
index 0000000..4c1fe20
--- /dev/null
+++ b/src/b64.c
@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) 2021 Chris Hiszpanski. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 3. The name of the author(s) may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "b64.h"
+
+void b64_encode(char *dst, const char *src, size_t size) {
+    const char lut[64] =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+    char spare = 0;
+    char state = 0;
+
+    while (size || spare) {
+        switch (state) {
+        case 0:
+            *dst++ = lut[((*src) >> 2) & 0x3F];
+            spare = (*src) & 0x3;
+            state = 1;
+            src++;
+            size--;
+            break;
+        case 1:
+            *dst++ = lut[(spare << 4) | (((*src) >> 4) & 0x0F)];
+            spare = (*src) & 0x0F;
+            state = 2;
+            src++;
+            size--;
+            break;
+        case 2:
+            *dst++ = lut[(spare << 2) | (((*src) >> 6) & 0x03)];
+            spare = (*src) & 0x3F;
+            state = 3;
+            size--;
+            break;
+        case 3:
+            *dst++ = lut[spare];
+            spare = 0;
+            state = 0;
+            break;
+        }
+    }
+    *dst = '\0';
+}
+
diff --git a/src/b64.h b/src/b64.h
new file mode 100644
index 0000000..fde7fc3
--- /dev/null
+++ b/src/b64.h
@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) 2021 Chris Hiszpanski. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 3. The name of the author(s) may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef URTC_B64_H
+#define URTC_B64_H
+
+#include <stddef.h>
+
+void b64_encode(char *dst, const char *src, size_t size);
+
+#endif // URTC_B64_H
diff --git a/src/urtc.c b/src/urtc.c
index f3ffa99..47c32b8 100644
--- a/src/urtc.c
+++ b/src/urtc.c
@@ -39,6 +39,7 @@
 #include <sys/socket.h>                 // socket
 #include <sys/types.h>
 
+#include "b64.h"                        // b64_encode
 #include "err.h"
 #include "log.h"
 #include "mdns.h"                       // mdns_subscribe, mdns_unsubscribe
@@ -426,6 +427,17 @@ int urtc_add_ice_candidate(struct peerconn *pc, const char *cand) {
 }
 
 int urtc_create_answer(struct peerconn *pc, char *answer, size_t size) {
+    char pwd[18]; // 24 base64 characters
+    char ufrag[3]; // 4 base64 characters
+
+    prng(pwd, sizeof(pwd));
+    prng(ufrag, sizeof(ufrag));
+
+    b64_encode(pc->ldesc.pwd, pwd, sizeof(pwd));
+    b64_encode(pc->ldesc.ufrag, ufrag, sizeof(ufrag));
+
+    pc->ldesc.mode = SDP_MODE_SEND_ONLY;
+
     return sdp_serialize(answer, size, &pc->ldesc);
 }