Introduce a buffer stack, and use it for ESP decryption.

[tcpdump] / print-esp.c

diff --git a/print-esp.c b/print-esp.c
index 60749992586ed1d40677a9c5e0037566b20d2f04..151be1d632676efae39856111092180bbbc59603 100644 (file)
--- a/print-esp.c
+++ b/print-esp.c
@@ -179,7 +179,16 @@ set_cipher_parameters(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
 #endif
 
 /*
- * this will adjust ndo_packetp and ndo_snapend to new buffer!
+ * This will allocate a new buffer containing the decrypted data.
+ * It returns 1 on success and 0 on failure.
+ *
+ * It will push the new buffer and the values of ndo->ndo_packetp and
+ * ndo->ndo_snapend onto the buffer stack, and change ndo->ndo_packetp
+ * and ndo->ndo_snapend to refer to the new buffer.
+ *
+ * Our caller must pop the buffer off the stack when it's finished
+ * dissecting anything in it and before it does any dissection of
+ * anything in the old buffer.  That will free the new buffer.
  */
 USES_APPLE_DEPRECATED_API
 int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
@@ -190,10 +199,12 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
 {
        struct sa_list *sa;
        const u_char *iv;
+       const u_char *ct;
        unsigned int len;
        EVP_CIPHER_CTX *ctx;
        unsigned int block_size, buffer_size;
        u_char *input_buffer, *output_buffer;
+       const u_char *pt;
 
        /* initiator arg is any non-zero value */
        if(initiator) initiator=1;
@@ -216,10 +227,10 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
         */
        end = end - sa->authlen;
        iv  = buf;
-       buf = buf + sa->ivlen;
-       len = end-buf;
+       ct = iv + sa->ivlen;
+       len = end-ct;
 
-       if(end <= buf) return 0;
+       if(end <= ct) return 0;
 
        ctx = EVP_CIPHER_CTX_new();
        if (ctx == NULL)
@@ -254,7 +265,7 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
         * Copy the input data to the encrypted data buffer, and pad it
         * with zeroes.
         */
-       memcpy(input_buffer, buf, len);
+       memcpy(input_buffer, ct, len);
        memset(input_buffer + len, 0, buffer_size - len);
 
        /*
@@ -274,15 +285,24 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
        EVP_CIPHER_CTX_free(ctx);
 
        /*
-        * XXX - of course this is wrong, because buf is a const buffer,
-        * but changing this would require a more complicated fix.
+        * Free the input buffer; we no longer need it.
         */
-       memcpy(buf, output_buffer, len);
        free(input_buffer);
-       free(output_buffer);
 
-       ndo->ndo_packetp = buf;
-       ndo->ndo_snapend = end;
+       /*
+        * Get a pointer to the plaintext.
+        */
+       pt = output_buffer;
+
+       /*
+        * Switch to the output buffer for dissection, and save it
+        * on the buffer stack so it can be freed; our caller must
+        * pop it when done.
+        */
+       if (!nd_push_buffer(ndo, output_buffer, pt, pt + len)) {
+               free(output_buffer);
+               return 0;
+       }
 
        return 1;
 }
@@ -695,6 +715,8 @@ esp_print(netdissect_options *ndo,
        EVP_CIPHER_CTX *ctx;
        unsigned int block_size, buffer_size;
        u_char *input_buffer, *output_buffer;
+       const u_char *pt;
+       u_int ptlen;
        u_int padlen;
        u_int nh;
 #endif
@@ -888,13 +910,28 @@ esp_print(netdissect_options *ndo,
        }
        free(input_buffer);
        EVP_CIPHER_CTX_free(ctx);
+
+       /*
+        * Pointer to the plaintext.
+        */
+       pt = output_buffer;
+
+       /*
+        * Length of the plaintext, which is the same as the length
+        * of the ciphertext.
+        */
+       ptlen = ctlen;
+
        /*
-        * XXX - of course this is wrong, because buf is a
-        * const buffer, but changing this would require a
-        * more complicated fix.
+        * Switch to the output buffer for dissection, and
+        * save it on the buffer stack so it can be freed.
         */
-       memcpy(ct, output_buffer, ctlen);
-       free(output_buffer);
+       if (!nd_push_buffer(ndo, output_buffer, pt, pt + ctlen)) {
+               free(output_buffer);
+               (*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
+                       "esp_print: can't push buffer on buffer stack");
+       }
+       ep = pt + ptlen;
 
        /*
         * Sanity check for pad length; if it, plus 2 for the pad
@@ -906,7 +943,7 @@ esp_print(netdissect_options *ndo,
         * "plaintext" is not what was being sent.
         */
        padlen = GET_U_1(ep - 2);
-       if (padlen + 2 > ctlen) {
+       if (padlen + 2 > ptlen) {
                nd_print_trunc(ndo);
                return;
        }
@@ -916,9 +953,12 @@ esp_print(netdissect_options *ndo,
 
        ND_PRINT(": ");
 
-       /* Now print the payload. */
-       ip_print_demux(ndo, ct, ctlen - (padlen + 2),  ver, fragmented,
+       /* Now dissect the plaintext. */
+       ip_print_demux(ndo, pt, ptlen - (padlen + 2), ver, fragmented,
            ttl_hl, nh, bp2);
+
+       /* Pop the buffer, freeing it. */
+       nd_pop_buffer(ndo);
 #endif
 }
 #ifdef HAVE_LIBCRYPTO