Fix escaping in generated recovery.conf file.

In the primary_conninfo line that "pg_basebackup -R" generates, single
quotes in parameter values need to be escaped into \\'; the libpq parser
requires the quotes to be escaped into \', and recovery.conf parser requires
the \ to be escaped into \\.

Also, don't quote parameter values unnecessarily, to make the connection
string prettier. Most options in a libpq connection string don't need
quoting.

Reported by Hari Babu, closer analysis by Zoltan Boszormenyi, although I
didn't use his patch.

src/bin/pg_basebackup/pg_basebackup.c

@@ -1107,7 +1107,71 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
 }
 
 /*
- * Escape single quotes used in connection parameters
+ * Escape a parameter value so that it can be used as part of a libpq
+ * connection string, e.g. in:
+ *
+ * application_name=<value>
+ *
+ * The returned string is malloc'd. Return NULL on out-of-memory.
+ */
+static char *
+escapeConnectionParameter(const char *src)
+{
+	bool		need_quotes = false;
+	bool		need_escaping = false;
+	const char *p;
+	char	   *dstbuf;
+	char	   *dst;
+
+	/*
+	 * First check if quoting is needed. Any quote (') or backslash (\)
+	 * characters need to be escaped. Parameters are separated by whitespace,
+	 * so any string containing whitespace characters need to be quoted. An
+	 * empty string is represented by ''.
+	 */
+	if (strchr(src, '\'') != NULL || strchr(src, '\\') != NULL)
+		need_escaping = true;
+
+	for (p = src; *p; p++)
+	{
+		if (isspace(*p))
+		{
+			need_quotes = true;
+			break;
+		}
+	}
+
+	if (*src == '\0')
+		return pg_strdup("''");
+
+	if (!need_quotes && !need_escaping)
+		return pg_strdup(src); /* no quoting or escaping needed */
+
+	/*
+	 * Allocate a buffer large enough for the worst case that all the source
+	 * characters need to be escaped, plus quotes.
+	 */
+	dstbuf = pg_malloc(strlen(src) * 2 + 2 + 1);
+
+	dst = dstbuf;
+	if (need_quotes)
+		*(dst++) = '\'';
+	for (; *src; src++)
+	{
+		if (*src == '\'' || *src == '\\')
+			*(dst++) = '\\';
+		*(dst++) = *src;
+	}
+	if (need_quotes)
+		*(dst++) = '\'';
+	*dst = '\0';
+
+	return dstbuf;
+}
+
+/*
+ * Escape a string so that it can be used as a value in a key-value pair
+ * a configuration file.
  */
 static char *
 escape_quotes(const char *src)
@@ -1130,6 +1194,8 @@ GenerateRecoveryConf(PGconn *conn)
 {
 	PQconninfoOption *connOptions;
 	PQconninfoOption *option;
+	PQExpBufferData conninfo_buf;
+	char	   *escaped;
 
 	recoveryconfcontents = createPQExpBuffer();
 	if (!recoveryconfcontents)
@@ -1146,12 +1212,10 @@ GenerateRecoveryConf(PGconn *conn)
 	}
 
 	appendPQExpBufferStr(recoveryconfcontents, "standby_mode = 'on'\n");
-	appendPQExpBufferStr(recoveryconfcontents, "primary_conninfo = '");
 
+	initPQExpBuffer(&conninfo_buf);
 	for (option = connOptions; option && option->keyword; option++)
 	{
-		char	   *escaped;
-
 		/*
 		 * Do not emit this setting if: - the setting is "replication",
 		 * "dbname" or "fallback_application_name", since these would be
@@ -1165,24 +1229,37 @@ GenerateRecoveryConf(PGconn *conn)
 			(option->val != NULL && option->val[0] == '\0'))
 			continue;
 
+		/* Separate key-value pairs with spaces */
+		if (conninfo_buf.len != 0)
+			appendPQExpBufferStr(&conninfo_buf, " ");
+
 		/*
-		 * Write "keyword='value'" pieces, the value string is escaped if
+		 * Write "keyword=value" pieces, the value string is escaped and/or
-		 * necessary and doubled single quotes around the value string.
+		 * quoted if necessary.
 		 */
-		escaped = escape_quotes(option->val);
+		escaped = escapeConnectionParameter(option->val);
-
+		appendPQExpBuffer(&conninfo_buf, "%s=%s", option->keyword, escaped);
-		appendPQExpBuffer(recoveryconfcontents, "%s=''%s'' ", option->keyword, escaped);
-
 		free(escaped);
 	}
 
-	appendPQExpBufferStr(recoveryconfcontents, "'\n");
+	/*
-	if (PQExpBufferBroken(recoveryconfcontents))
+	 * Escape the connection string, so that it can be put in the config file.
+	 * Note that this is different from the escaping of individual connection
+	 * options above!
+	 */
+	escaped = escape_quotes(conninfo_buf.data);
+	appendPQExpBuffer(recoveryconfcontents, "primary_conninfo = '%s'\n", escaped);
+	free(escaped);
+
+	if (PQExpBufferBroken(recoveryconfcontents) ||
+		PQExpBufferDataBroken(conninfo_buf))
 	{
 		fprintf(stderr, _("%s: out of memory\n"), progname);
 		disconnect_and_exit(1);
 	}
 
+	termPQExpBuffer(&conninfo_buf);
+
 	PQconninfoFree(connOptions);
 }