From 4944b4ddd5dfb00c2b573887c6f4919c40c9391a Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Tue, 21 Dec 2021 13:25:19 +0000
Subject: [PATCH] Remove duplicated string-literal formatter in Telnet proxy.

Now it's done using the same code as in write_c_string_literal(), by
means of factoring the latter into a version that targets any old
BinarySink and a convenience wrapper taking a FILE *.
---
 marshal.h                      |  5 +++++
 proxy/telnet.c                 | 19 +------------------
 utils/write_c_string_literal.c | 30 +++++++++++++++++++-----------
 3 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/marshal.h b/marshal.h
index 515f0e53..4d5b0075 100644
--- a/marshal.h
+++ b/marshal.h
@@ -152,6 +152,10 @@ struct BinarySink {
 #define put_fmtv(bs, fmt, ap) \
     BinarySink_put_fmtv(BinarySink_UPCAST(bs), fmt, ap)
 
+/* More complicated function implemented in write_c_string_literal.c */
+#define put_c_string_literal(bs, str) \
+    BinarySink_put_c_string_literal(BinarySink_UPCAST(bs), str)
+
 /*
  * The underlying real C functions that implement most of those
  * macros. Generally you won't want to call these directly, because
@@ -180,6 +184,7 @@ void BinarySink_put_mp_ssh1(BinarySink *bs, mp_int *x);
 void BinarySink_put_mp_ssh2(BinarySink *bs, mp_int *x);
 void BinarySink_put_fmt(BinarySink *, const char *fmt, ...) PRINTF_LIKE(2, 3);
 void BinarySink_put_fmtv(BinarySink *, const char *fmt, va_list ap);
+void BinarySink_put_c_string_literal(BinarySink *, ptrlen);
 
 /* ---------------------------------------------------------------------- */
 
diff --git a/proxy/telnet.c b/proxy/telnet.c
index e0a54450..1b4a5326 100644
--- a/proxy/telnet.c
+++ b/proxy/telnet.c
@@ -336,25 +336,8 @@ static void proxy_telnet_process_queue(ProxyNegotiator *pn)
             pn->ps->remote_addr, pn->ps->remote_port, s->conf, NULL);
 
         strbuf *logmsg = strbuf_new();
-        const char *in;
-
         put_datapl(logmsg, PTRLEN_LITERAL("Sending Telnet proxy command: "));
-
-        for (in = censored_cmd; *in; in++) {
-            if (*in == '\n') {
-                put_datapl(logmsg, PTRLEN_LITERAL("\\n"));
-            } else if (*in == '\r') {
-                put_datapl(logmsg, PTRLEN_LITERAL("\\r"));
-            } else if (*in == '\t') {
-                put_datapl(logmsg, PTRLEN_LITERAL("\\t"));
-            } else if (*in == '\\') {
-                put_datapl(logmsg, PTRLEN_LITERAL("\\\\"));
-            } else if (0x20 <= *in && *in < 0x7F) {
-                put_byte(logmsg, *in);
-            } else {
-                put_fmt(logmsg, "\\x%02X", (unsigned)*in & 0xFF);
-            }
-        }
+        put_c_string_literal(logmsg, ptrlen_from_asciz(censored_cmd));
 
         plug_log(pn->ps->plug, PLUGLOG_PROXY_MSG, NULL, 0, logmsg->s, 0);
         strbuf_free(logmsg);
diff --git a/utils/write_c_string_literal.c b/utils/write_c_string_literal.c
index 6415c287..e8b2f53b 100644
--- a/utils/write_c_string_literal.c
+++ b/utils/write_c_string_literal.c
@@ -1,31 +1,39 @@
 /*
- * Write data to a file in the form of a C string literal, with any
- * non-printable-ASCII character escaped appropriately.
+ * Write data to a file or BinarySink in the form of a C string
+ * literal, with any non-printable-ASCII character escaped
+ * appropriately.
  */
 
 #include "defs.h"
 #include "misc.h"
 
-void write_c_string_literal(FILE *fp, ptrlen str)
+void BinarySink_put_c_string_literal(BinarySink *bs, ptrlen str)
 {
     for (const char *p = str.ptr; p < (const char *)str.ptr + str.len; p++) {
         char c = *p;
 
         if (c == '\n')
-            fputs("\\n", fp);
+            put_datalit(bs, "\\n");
         else if (c == '\r')
-            fputs("\\r", fp);
+            put_datalit(bs, "\\r");
         else if (c == '\t')
-            fputs("\\t", fp);
+            put_datalit(bs, "\\t");
         else if (c == '\b')
-            fputs("\\b", fp);
+            put_datalit(bs, "\\b");
         else if (c == '\\')
-            fputs("\\\\", fp);
+            put_datalit(bs, "\\\\");
         else if (c == '"')
-            fputs("\\\"", fp);
+            put_datalit(bs, "\\\"");
         else if (c >= 32 && c <= 126)
-            fputc(c, fp);
+            put_byte(bs, c);
         else
-            fprintf(fp, "\\%03o", (unsigned char)c);
+            put_fmt(bs, "\\%03o", (unsigned)c & 0xFFU);
     }
 }
+
+void write_c_string_literal(FILE *fp, ptrlen str)
+{
+    stdio_sink s;
+    stdio_sink_init(&s, fp);
+    put_c_string_literal(&s, str);
+}