From 55674c369be3dadf1bd2a64cfeb209705ee52d46 Mon Sep 17 00:00:00 2001
From: LDA <lda@ari.lt>
Date: Mon, 26 Aug 2024 21:07:55 +0200
Subject: [PATCH] [MOD] Avoid allocating memory in HMAC

---
 Makefile          |  2 +-
 src/Main.c        |  9 +++++----
 src/Parsee/HMAC.c | 29 ++++++++++++-----------------
 3 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/Makefile b/Makefile
index 82d651a..c76e361 100644
--- a/Makefile
+++ b/Makefile
@@ -41,7 +41,7 @@ all: binary utils
 
 binary: $(OBJ_FILES)
 	$(CC) $(LDFLAGS) $(OBJ_FILES) -o $(BINARY)
-tags:
+tags: $(SRC_FILES)
 	@ctags --recurse $(SOURCE)/
 
 clean:
diff --git a/src/Main.c b/src/Main.c
index 3303db1..fd599ba 100644
--- a/src/Main.c
+++ b/src/Main.c
@@ -42,12 +42,13 @@ static const Argument arguments[] =
     Arg('J', true, "number(=8)", "Sets the number of XMPP threads")
     Arg('C', true, "file(='parsee.json')", "Sets the JSON config to use")
 
-    Arg('g', false, NULL,"Generates a parsee.yaml AS file before exiting")
+    Arg('g', false, NULL,
+        "Generates a parsee.yaml AS file before exiting")
     Arg('v', false, NULL,
         "Forces Parsee to print in a more verbose fashion "
-        "(-vv prints stanzas to stderr)"
-    )
-    Arg('h', false, NULL,"Generates an help screen(this one!)")
+        "(-vv prints stanzas to stderr)")
+    Arg('h', false, NULL,
+        "Generates an help screen(this one!)")
 
     EndOfArgs
 
diff --git a/src/Parsee/HMAC.c b/src/Parsee/HMAC.c
index 3904ebc..efdd09a 100644
--- a/src/Parsee/HMAC.c
+++ b/src/Parsee/HMAC.c
@@ -8,13 +8,11 @@
 
 #include <string.h>
 
-/* A 64-byte key! */
-static uint8_t *
-ComputeKPad(char *key, uint8_t pad)
+static void
+ComputeKPad(char *key, uint8_t pad, uint8_t *kopad)
 {
     size_t klen;
     uint8_t *kp;
-    uint8_t *kopad;
     size_t i;
     if ((klen = strlen(key)) <= 64)
     {
@@ -28,7 +26,6 @@ ComputeKPad(char *key, uint8_t pad)
     }
 
     /* Now that we have K', lets compute it XORd with opad */
-    kopad = Malloc(64 * sizeof(uint8_t));
     for (i = 0; i < 64; i++)
     {
         uint8_t byte = i < klen ? kp[i] : 0x00;
@@ -36,41 +33,39 @@ ComputeKPad(char *key, uint8_t pad)
     }
 
     Free(kp);
-    return kopad;
 }
 
 char *
 ParseeHMAC(char *key, uint8_t *msg, size_t msglen)
 {
-    uint8_t *opad, *ipad;
+    uint8_t opad[64], ipad[64 + msglen];
+    uint8_t outer[64 + 32];
+
     uint8_t *innersha;
-    uint8_t *outer;
-    unsigned char *sha;
+    uint8_t *sha;
     char *str;
     if (!key || !msg || !msglen)
     {
         return NULL;
     }
 
-    opad = ComputeKPad(key, 0x5C);
+    /* Initialise K' XOR opad and K' XOR ipad */
+    ComputeKPad(key, 0x5C, opad);
+    ComputeKPad(key, 0x36, ipad);
 
-    ipad = ComputeKPad(key, 0x36);
-    ipad = Realloc(ipad, 64 + msglen);
+    /* Compute H((K' XOR ipad) || msg) */
     memcpy(ipad + 64, msg, msglen);
     innersha = Sha256Raw(ipad, 64 + msglen);
 
-    outer = Malloc(64 + 32);
+    /* Compute (K' XOR opad) || H((K' XOR ipad) || msg) */
     memcpy(outer, opad, 64);
     memcpy(outer + 64, innersha, 32);
 
+    /* Compute H((K' XOR opad) || H((K' XOR ipad) || msg)) */
     sha = Sha256Raw(outer, 64 + 32);
     str = ShaToHex(sha, HASH_SHA256);
 
     Free(innersha);
-    Free(outer);
-    Free(ipad);
-    Free(opad);
     Free(sha);
-
     return str;
 }