Add Lua interface to HTTPFetchRequest

This allows mods to perform both asynchronous and synchronous HTTP
requests. Mods are only granted access to HTTP APIs if either mod
security is disabled or if they are whitelisted in any of the
the secure.http_mods and secure.trusted_mods settings.

Adds httpfetch_caller_alloc_secure to generate random, non-predictable
caller IDs so that lua mods cannot spy on each others HTTP queries.

1 files changed, 36 insertions, 1 deletions

diff --git a/src/httpfetch.cpp b/src/httpfetch.cpp
index 1a19dd082..f64c9f717 100644
--- a/src/httpfetch.cpp
+++ b/src/httpfetch.cpp
@@ -18,7 +18,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 */
 
 #include "socket.h" // for select()
-#include "porting.h" // for sleep_ms(), get_sysinfo()
+#include "porting.h" // for sleep_ms(), get_sysinfo(), secure_rand_fill_buf()
 #include "httpfetch.h"
 #include <iostream>
 #include <sstream>
@@ -34,9 +34,11 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "util/thread.h"
 #include "version.h"
 #include "settings.h"
+#include "noise.h"
 
 Mutex g_httpfetch_mutex;
 std::map<unsigned long, std::queue<HTTPFetchResult> > g_httpfetch_results;
+PcgRandom g_callerid_randomness;
 
 HTTPFetchRequest::HTTPFetchRequest()
 {
@@ -84,6 +86,34 @@ unsigned long httpfetch_caller_alloc()
 	return discard;
 }
 
+unsigned long httpfetch_caller_alloc_secure()
+{
+	MutexAutoLock lock(g_httpfetch_mutex);
+
+	// Generate random caller IDs and make sure they're not
+	// already used or equal to HTTPFETCH_DISCARD
+	// Give up after 100 tries to prevent infinite loop
+	u8 tries = 100;
+	unsigned long caller;
+
+	do {
+		caller = (((u64) g_callerid_randomness.next()) << 32) |
+				g_callerid_randomness.next();
+
+		if (--tries < 1) {
+			FATAL_ERROR("httpfetch_caller_alloc_secure: ran out of caller IDs");
+			return HTTPFETCH_DISCARD;
+		}
+	} while (g_httpfetch_results.find(caller) != g_httpfetch_results.end());
+
+	verbosestream << "httpfetch_caller_alloc_secure: allocating "
+		<< caller << std::endl;
+
+	// Access element to create it
+	g_httpfetch_results[caller];
+	return caller;
+}
+
 void httpfetch_caller_free(unsigned long caller)
 {
 	verbosestream<<"httpfetch_caller_free: freeing "
@@ -710,6 +740,11 @@ void httpfetch_init(int parallel_limit)
 	FATAL_ERROR_IF(res != CURLE_OK, "CURL init failed");
 
 	g_httpfetch_thread = new CurlFetchThread(parallel_limit);
+
+	// Initialize g_callerid_randomness for httpfetch_caller_alloc_secure
+	u64 randbuf[2];
+	porting::secure_rand_fill_buf(randbuf, sizeof(u64) * 2);
+	g_callerid_randomness = PcgRandom(randbuf[0], randbuf[1]);
 }
 
 void httpfetch_cleanup()