Add read and write support to tls_buffer.

tls_buffer was original created for a specific use case, namely reading in
length prefixed messages. This adds read and write support, along with a
capacity limit, allowing it to be used in additional use cases.

ok beck@ tb@

4 files changed, 139 insertions, 13 deletions

diff --git a/src/lib/libssl/tls13_handshake_msg.c b/src/lib/libssl/tls13_handshake_msg.c
index 946ccaccd6..134cfb2173 100644
--- a/src/lib/libssl/tls13_handshake_msg.c
+++ b/src/lib/libssl/tls13_handshake_msg.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_handshake_msg.c,v 1.5 2022/07/20 06:32:24 jsing Exp $ */
+/* $OpenBSD: tls13_handshake_msg.c,v 1.6 2022/07/22 19:33:53 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
  *
@@ -136,7 +136,8 @@ tls13_handshake_msg_recv(struct tls13_handshake_msg *msg,
                     tls13_handshake_msg_read_cb, rl)) <= 0)
                         return ret;
 
-                tls_buffer_cbs(msg->buf, &cbs);
+                if (!tls_buffer_data(msg->buf, &cbs))
+                        return TLS13_IO_FAILURE;
 
                 if (!CBS_get_u8(&cbs, &msg_type))
                         return TLS13_IO_FAILURE;
diff --git a/src/lib/libssl/tls13_record.c b/src/lib/libssl/tls13_record.c
index 2c744668e5..dbc835c546 100644
--- a/src/lib/libssl/tls13_record.c
+++ b/src/lib/libssl/tls13_record.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_record.c,v 1.9 2021/10/23 13:12:14 jsing Exp $ */
+/* $OpenBSD: tls13_record.c,v 1.10 2022/07/22 19:33:53 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
  *
@@ -134,7 +134,8 @@ tls13_record_recv(struct tls13_record *rec, tls_read_cb wire_read,
                     TLS13_RECORD_HEADER_LEN, wire_read, wire_arg)) <= 0)
                         return ret;
 
-                tls_buffer_cbs(rec->buf, &cbs);
+                if (!tls_buffer_data(rec->buf, &cbs))
+                        return TLS13_IO_FAILURE;
 
                 if (!CBS_get_u8(&cbs, &content_type))
                         return TLS13_IO_FAILURE;
diff --git a/src/lib/libssl/tls_buffer.c b/src/lib/libssl/tls_buffer.c
index 9bb6b62e51..f70cfbc1a0 100644
--- a/src/lib/libssl/tls_buffer.c
+++ b/src/lib/libssl/tls_buffer.c
@@ -1,6 +1,6 @@
-/* $OpenBSD: tls_buffer.c,v 1.2 2022/07/20 06:32:24 jsing Exp $ */
+/* $OpenBSD: tls_buffer.c,v 1.3 2022/07/22 19:33:53 jsing Exp $ */
 /*
- * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
+ * Copyright (c) 2018, 2019, 2022 Joel Sing <jsing@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -21,8 +21,11 @@
 #include "bytestring.h"
 #include "tls_internal.h"
 
+#define TLS_BUFFER_CAPACITY_LIMIT       (1024 * 1024)
+
 struct tls_buffer {
         size_t capacity;
+        size_t capacity_limit;
         uint8_t *data;
         size_t len;
         size_t offset;
@@ -38,6 +41,8 @@ tls_buffer_new(size_t init_size)
         if ((buf = calloc(1, sizeof(struct tls_buffer))) == NULL)
                 goto err;
 
+        buf->capacity_limit = TLS_BUFFER_CAPACITY_LIMIT;
+
         if (!tls_buffer_resize(buf, init_size))
                 goto err;
 
@@ -50,32 +55,76 @@ tls_buffer_new(size_t init_size)
 }
 
 void
+tls_buffer_clear(struct tls_buffer *buf)
+{
+        freezero(buf->data, buf->capacity);
+
+        buf->data = NULL;
+        buf->capacity = 0;
+        buf->len = 0;
+        buf->offset = 0;
+}
+
+void
 tls_buffer_free(struct tls_buffer *buf)
 {
         if (buf == NULL)
                 return;
 
-        freezero(buf->data, buf->capacity);
+        tls_buffer_clear(buf);
+
         freezero(buf, sizeof(struct tls_buffer));
 }
 
 static int
+tls_buffer_grow(struct tls_buffer *buf, size_t capacity)
+{
+        if (buf->capacity >= capacity)
+                return 1;
+
+        return tls_buffer_resize(buf, capacity);
+}
+
+static int
 tls_buffer_resize(struct tls_buffer *buf, size_t capacity)
 {
         uint8_t *data;
 
+        /*
+         * XXX - Consider maintaining a minimum size and growing more
+         * intelligently (rather than exactly).
+         */
         if (buf->capacity == capacity)
                 return 1;
 
+        if (capacity > buf->capacity_limit)
+                return 0;
+
         if ((data = recallocarray(buf->data, buf->capacity, capacity, 1)) == NULL)
                 return 0;
 
         buf->data = data;
         buf->capacity = capacity;
 
+        /* Ensure that len and offset are valid if capacity decreased. */
+        if (buf->len > buf->capacity)
+                buf->len = buf->capacity;
+        if (buf->offset > buf->len)
+                buf->offset = buf->len;
+
         return 1;
 }
 
+void
+tls_buffer_set_capacity_limit(struct tls_buffer *buf, size_t limit)
+{
+        /*
+         * XXX - do we want to force a resize if this limit is less than current
+         * capacity... and what do we do with existing data? Force a clear?
+         */
+        buf->capacity_limit = limit;
+}
+
 ssize_t
 tls_buffer_extend(struct tls_buffer *buf, size_t len,
     tls_read_cb read_cb, void *cb_arg)
@@ -106,10 +155,79 @@ tls_buffer_extend(struct tls_buffer *buf, size_t len,
         }
 }
 
-void
-tls_buffer_cbs(struct tls_buffer *buf, CBS *cbs)
+ssize_t
+tls_buffer_read(struct tls_buffer *buf, uint8_t *rbuf, size_t n)
+{
+        if (buf->offset > buf->len)
+                return TLS_IO_FAILURE;
+
+        if (buf->offset == buf->len)
+                return TLS_IO_WANT_POLLIN;
+
+        if (n > buf->len - buf->offset)
+                n = buf->len - buf->offset;
+
+        memcpy(rbuf, &buf->data[buf->offset], n);
+
+        buf->offset += n;
+
+        return n;
+}
+
+ssize_t
+tls_buffer_write(struct tls_buffer *buf, const uint8_t *wbuf, size_t n)
+{
+        if (buf->offset > buf->len)
+                return TLS_IO_FAILURE;
+
+        /*
+         * To avoid continually growing the buffer, pull data up to the
+         * start of the buffer. If all data has been read then we can simply
+         * reset, otherwise wait until we're going to save at least 4KB of
+         * memory to reduce overhead.
+         */
+        if (buf->offset == buf->len) {
+                buf->len = 0;
+                buf->offset = 0;
+        }
+        if (buf->offset >= 4096) {
+                memmove(buf->data, &buf->data[buf->offset],
+                    buf->len - buf->offset);
+                buf->len -= buf->offset;
+                buf->offset = 0;
+        }
+
+        if (buf->len > SIZE_MAX - n)
+                return TLS_IO_FAILURE;
+        if (!tls_buffer_grow(buf, buf->len + n))
+                return TLS_IO_FAILURE;
+
+        memcpy(&buf->data[buf->len], wbuf, n);
+
+        buf->len += n;
+
+        return n;
+}
+
+int
+tls_buffer_append(struct tls_buffer *buf, const uint8_t *wbuf, size_t n)
+{
+        return tls_buffer_write(buf, wbuf, n) == n;
+}
+
+int
+tls_buffer_data(struct tls_buffer *buf, CBS *out_cbs)
 {
-        CBS_init(cbs, buf->data, buf->len);
+        CBS cbs;
+
+        CBS_init(&cbs, buf->data, buf->len);
+
+        if (!CBS_skip(&cbs, buf->offset))
+                return 0;
+
+        CBS_dup(&cbs, out_cbs);
+
+        return 1;
 }
 
 int
@@ -121,9 +239,10 @@ tls_buffer_finish(struct tls_buffer *buf, uint8_t **out, size_t *out_len)
         *out = buf->data;
         *out_len = buf->len;
 
-        buf->capacity = 0;
         buf->data = NULL;
+        buf->capacity = 0;
         buf->len = 0;
+        buf->offset = 0;
 
         return 1;
 }
diff --git a/src/lib/libssl/tls_internal.h b/src/lib/libssl/tls_internal.h
index ac2d14da48..88dae9e67e 100644
--- a/src/lib/libssl/tls_internal.h
+++ b/src/lib/libssl/tls_internal.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_internal.h,v 1.7 2022/07/20 06:32:24 jsing Exp $ */
+/* $OpenBSD: tls_internal.h,v 1.8 2022/07/22 19:33:53 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019, 2021 Joel Sing <jsing@openbsd.org>
  *
@@ -47,10 +47,15 @@ typedef ssize_t (*tls_flush_cb)(void *_cb_arg);
 struct tls_buffer;
 
 struct tls_buffer *tls_buffer_new(size_t init_size);
+void tls_buffer_clear(struct tls_buffer *buf);
 void tls_buffer_free(struct tls_buffer *buf);
+void tls_buffer_set_capacity_limit(struct tls_buffer *buf, size_t limit);
 ssize_t tls_buffer_extend(struct tls_buffer *buf, size_t len,
     tls_read_cb read_cb, void *cb_arg);
-void tls_buffer_cbs(struct tls_buffer *buf, CBS *cbs);
+ssize_t tls_buffer_read(struct tls_buffer *buf, uint8_t *rbuf, size_t n);
+ssize_t tls_buffer_write(struct tls_buffer *buf, const uint8_t *wbuf, size_t n);
+int tls_buffer_append(struct tls_buffer *buf, const uint8_t *wbuf, size_t n);
+int tls_buffer_data(struct tls_buffer *buf, CBS *cbs);
 int tls_buffer_finish(struct tls_buffer *buf, uint8_t **out, size_t *out_len);
 
 /*