Make the ESP decryption not crash with OpenSSL 1.1.

While we're at it, free the cipher context if we fail to allocate the
output buffer for decryption.

1 files changed, 39 insertions, 4 deletions

diff --git a/print-esp.c b/print-esp.c
index f2b4ab3c..d12b97da 100644
--- a/print-esp.c
+++ b/print-esp.c
@@ -145,6 +145,39 @@ EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx)
 }
 #endif
 
+#ifdef HAVE_EVP_CIPHERINIT_EX
+/*
+ * Initialize the cipher by calling EVP_CipherInit_ex(), because
+ * calling EVP_CipherInit() will reset the cipher context, clearing
+ * the cipher, so calling it twice, with the second call having a
+ * null cipher, will clear the already-set cipher.  EVP_CipherInit_ex(),
+ * however, won't reset the cipher context, so you can use it to specify
+ * the IV oin a second call after a first call to EVP_CipherInit_ex()
+ * to set the cipher and the key.
+ *
+ * XXX - is there some reason why we need to make two calls?
+ */
+static int
+set_cipher_parameters(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
+		      const unsigned char *key,
+		      const unsigned char *iv, int enc)
+{
+	return EVP_CipherInit_ex(ctx, cipher, NULL, key, iv, enc);
+}
+#else
+/*
+ * Initialize the cipher by calling EVP_CipherInit(), because we don't
+ * have EVP_CipherInit_ex(); we rely on it not trashing the context.
+ */
+static int
+set_cipher_parameters(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
+		      const unsigned char *key,
+		      const unsigned char *iv, int enc)
+{
+	return EVP_CipherInit(ctx, cipher, key, iv, enc);
+}
+#endif
+
 /*
  * this will adjust ndo_packetp and ndo_snapend to new buffer!
  */
@@ -190,9 +223,9 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
 	ctx = EVP_CIPHER_CTX_new();
 	if (ctx == NULL)
 		return 0;
-	if (EVP_CipherInit(ctx, sa->evp, sa->secret, NULL, 0) < 0)
+	if (set_cipher_parameters(ctx, sa->evp, sa->secret, NULL, 0) < 0)
 		(*ndo->ndo_warning)(ndo, "espkey init failed");
-	EVP_CipherInit(ctx, NULL, NULL, iv, 0);
+	set_cipher_parameters(ctx, NULL, NULL, iv, 0);
 	/*
 	 * Allocate a buffer for the decrypted data.
 	 * The output buffer must be separate from the input buffer, and
@@ -203,6 +236,7 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
 	output_buffer = (u_char *)malloc(output_buffer_size);
 	if (output_buffer == NULL) {
 		(*ndo->ndo_warning)(ndo, "can't allocate memory for decryption buffer");
+		EVP_CIPHER_CTX_free(ctx);
 		return 0;
 	}
 	EVP_Cipher(ctx, output_buffer, buf, len);
@@ -735,11 +769,11 @@ esp_print(netdissect_options *ndo,
 	if (sa->evp) {
 		ctx = EVP_CIPHER_CTX_new();
 		if (ctx != NULL) {
-			if (EVP_CipherInit(ctx, sa->evp, secret, NULL, 0) < 0)
+			if (set_cipher_parameters(ctx, sa->evp, secret, NULL, 0) < 0)
 				(*ndo->ndo_warning)(ndo, "espkey init failed");
 
 			p = ivoff;
-			EVP_CipherInit(ctx, NULL, NULL, p, 0);
+			set_cipher_parameters(ctx, NULL, NULL, p, 0);
 			len = ep - (p + ivlen);
 
 			/*
@@ -753,6 +787,7 @@ esp_print(netdissect_options *ndo,
 			output_buffer = (u_char *)malloc(output_buffer_size);
 			if (output_buffer == NULL) {
 				(*ndo->ndo_warning)(ndo, "can't allocate memory for decryption buffer");
+				EVP_CIPHER_CTX_free(ctx);
 				return -1;
 			}