ccx-utils

commit 526fce1ea18343535048def444d86cc2cf22da98
parent 6a91f5a9d2af86320aef98b04ce1915c718b7da0
Author: Jan Pobrislo <ccx@te2000.cz>
Date:   Sun,  6 Oct 2024 15:05:11 +0000

Basic parsing and HMAC computation in miniroon

Diffstat:
M
src/miniroon.c
 | 
78
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------

1 file changed, 65 insertions(+), 13 deletions(-)
diff --git a/src/miniroon.c b/src/miniroon.c
@@ -42,7 +42,17 @@ typedef struct miniroon_header_s {
 
 } miniroon_header;
 
+/* declarations */
+void parse_payload(bytebuffer *payload);
+void parse_header(miniroon_header *header, bytebuffer *source);
+void parse_caveat(bytebuffer *source);  // TODO
+void read_secret(bytebuffer *secret);  // TODO
+void hmac_b2s_256(const bytebuffer *key, const bytebuffer *msg, bytebuffer *output);
 
+#define MINIROON_HMAC_SIZE 32
+#define MINIROON_HMAC_FUNC(key, msg, out) hmac_b2s_256(key, msg, out)
+
+/* definitions */
 void netstring_chunk_init (netstring_chunk *chunk, const bytebuffer source) {
   memset(chunk, 0, sizeof(netstring_chunk));
   chunk->source = source;
@@ -122,7 +132,7 @@ void parse_header(miniroon_header *header, bytebuffer *outer) {
 
 }
 
-int handle_payload(size_t payload_size) {
+void handle_payload(size_t payload_size) {
   char payload[payload_size+1];
   char *read_next = payload;
   ssize_t read_size;
@@ -143,22 +153,62 @@ int handle_payload(size_t payload_size) {
       strerr_dief1x(111, "Invalid netstring terminator");
   }
 
-  bytebuffer input, chunk, next;
-  input.data = payload;
-  input.len = payload_size;
+  bytebuffer payload_bb = {payload, payload_size};
+  parse_payload(&payload_bb);
+}
 
-  if(!netstring_get_chunk(&input, &chunk, &next)) {
-    strerr_dief1x(111, "Malformed netstring");
+void parse_caveat(bytebuffer *source) {
+  // TODO
+}
+
+void read_secret(bytebuffer *secret){
+  assert(secret->len == MINIROON_HMAC_SIZE);
+  // TODO
+  memset(secret->data, 0, secret->len);
+}
+
+void parse_payload(bytebuffer *payload) {
+  netstring_chunk c;
+  netstring_chunk_init(&c, *payload);
+
+  if(!netstring_chunk_next(&c)) {
+    strerr_dief1x(111, "Mising miniroon header");
   }
   miniroon_header hdr;
-  parse_header(&hdr, &chunk);
+  parse_header(&hdr, &c.inner);
+  // header should be verified by now, we can start hashing
+  uint8_t hmac_data[MINIROON_HMAC_SIZE];
+  bytebuffer hmac_bb = {hmac_data, MINIROON_HMAC_SIZE};
+  read_secret(&hmac_bb);
+  MINIROON_HMAC_FUNC(&hmac_bb, &c.inner, &hmac_bb);
+
+  if(!netstring_chunk_next(&c)) {
+    strerr_dief1x(111, "Mising miniroon body");
+  }
+  netstring_chunk body;
+  netstring_chunk_init(&body, c.inner);
 
-  while(next.len) {
-    input = next;
-    if(!netstring_get_chunk(&input, &chunk, &next)) {
-      strerr_dief1x(111, "Malformed netstring");
-    }
+  while(netstring_chunk_next(&body)) {
+    parse_caveat(&body.inner);
+    MINIROON_HMAC_FUNC(&hmac_bb, &body.inner, &hmac_bb);
+  }
 
+  if(!netstring_chunk_next(&c)) {
+    strerr_dief1x(111, "Mising miniroon signature");
+  }
+  if(c.inner.len != MINIROON_HMAC_SIZE) {
+    strerr_dief1x(111, "Mising miniroon signature length");
+  }
+  /* constant time hash compare */
+  uint8_t bitdiff = 0;
+  for(size_t i=0; i<=MINIROON_HMAC_SIZE; i++) {
+    bitdiff |= hmac_data[i] ^ c.inner.data[i];
+  }
+  if(netstring_chunk_next(&c)) {
+    strerr_dief1x(111, "Extraneous data in miniroon");
+  }
+  if(bitdiff) {
+    strerr_dief1x(111, "Invalid miniroon signature");
   }
 }
 
@@ -232,7 +282,9 @@ int main (int argc, char const *const *argv)
         break;
       case 1:
         if(read_char == ':') {
-          return handle_payload(payload_size);
+          handle_payload(payload_size);
+          strerr_dief1x(110, "Internal logic error, should not get here");
+          return 1;
         } else if(read_char >= '0' && read_char <= '9') {
           payload_size *= 10;
           payload_size += read_char - '0';