Put the crypto stuff into a common routine.

That makes it easier to 1) change it and 2) use different crypto
libraries for it.

1 files changed, 96 insertions, 138 deletions

diff --git a/print-esp.c b/print-esp.c
index ae8cb038..844522ec 100644
--- a/print-esp.c
+++ b/print-esp.c
@@ -178,6 +178,92 @@ set_cipher_parameters(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
 }
 #endif
 
+static u_char *
+do_decrypt(netdissect_options *ndo, const char *caller, struct sa_list *sa,
+    const u_char *iv, const u_char *ct, unsigned int ctlen)
+{
+	EVP_CIPHER_CTX *ctx;
+	unsigned int block_size;
+	unsigned int ptlen;
+	u_char *pt;
+	int len;
+
+	ctx = EVP_CIPHER_CTX_new();
+	if (ctx == NULL) {
+		/*
+		 * Failed to initialize the cipher context.
+		 * From a look at the OpenSSL code, this appears to
+		 * mean "couldn't allocate memory for the cipher context";
+		 * note that we're not passing any parameters, so there's
+		 * not much else it can mean.
+		 */
+		(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
+		    "%s: can't allocate memory for cipher context", caller);
+		return NULL;
+	}
+
+	if (set_cipher_parameters(ctx, sa->evp, sa->secret, NULL) < 0) {
+		EVP_CIPHER_CTX_free(ctx);
+		(*ndo->ndo_warning)(ndo, "%s: espkey init failed", caller);
+		return NULL;
+	}
+	if (set_cipher_parameters(ctx, NULL, NULL, iv) < 0) {
+		EVP_CIPHER_CTX_free(ctx);
+		(*ndo->ndo_warning)(ndo, "%s: IV init failed", caller);
+		return NULL;
+	}
+
+	/*
+	 * At least as I read RFC 5996 section 3.14 and RFC 4303 section 2.4,
+	 * if the cipher has a block size of which the ciphertext's size must
+	 * be a multiple, the payload must be padded to make that happen, so
+	 * the ciphertext length must be a multiple of the block size.  Fail
+	 * if that's not the case.
+	 */
+	block_size = (unsigned int)EVP_CIPHER_CTX_block_size(ctx);
+	if ((ctlen % block_size) != 0) {
+		EVP_CIPHER_CTX_free(ctx);
+		(*ndo->ndo_warning)(ndo,
+		    "%s: ciphertext size %u is not a multiple of the cipher block size %u",
+		    caller, ctlen, block_size);
+		return NULL;
+	}
+
+	/*
+	 * Attempt to allocate a buffer for the decrypted data, because
+	 * we can't decrypt on top of the input buffer.
+	 */
+	ptlen = ctlen;
+	pt = (u_char *)malloc(ptlen);
+	if (pt == NULL) {
+		EVP_CIPHER_CTX_free(ctx);
+		(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
+		    "%s: can't allocate memory for decryption buffer", caller);
+		return NULL;
+	}
+
+	/*
+	 * The size of the ciphertext handed to us is a multiple of the
+	 * cipher block size, so we don't need to worry about padding.
+	 */
+	if (!EVP_CIPHER_CTX_set_padding(ctx, 0)) {
+		free(pt);
+		EVP_CIPHER_CTX_free(ctx);
+		(*ndo->ndo_warning)(ndo,
+		    "%s: EVP_CIPHER_CTX_set_padding failed", caller);
+		return NULL;
+	}
+	if (!EVP_DecryptUpdate(ctx, pt, &len, ct, ctlen)) {
+		free(pt);
+		EVP_CIPHER_CTX_free(ctx);
+		(*ndo->ndo_warning)(ndo, "%s: EVP_DecryptUpdate failed",
+		    caller);
+		return NULL;
+	}
+	EVP_CIPHER_CTX_free(ctx);
+	return pt;
+}
+
 /*
  * This will allocate a new buffer containing the decrypted data.
  * It returns 1 on success and 0 on failure.
@@ -201,11 +287,7 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
 	const u_char *iv;
 	const u_char *ct;
 	unsigned int ctlen;
-	int len;
-	EVP_CIPHER_CTX *ctx;
-	unsigned int block_size;
 	u_char *pt;
-	u_int ptlen;
 
 	/* initiator arg is any non-zero value */
 	if(initiator) initiator=1;
@@ -233,64 +315,10 @@ int esp_print_decrypt_buffer_by_ikev2(netdissect_options *ndo,
 
 	if(end <= ct) return 0;
 
-	ctx = EVP_CIPHER_CTX_new();
-	if (ctx == NULL)
-		return 0;
-	if (set_cipher_parameters(ctx, sa->evp, sa->secret, NULL) < 0) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "espkey init failed");
-		return 0;
-	}
-	if (set_cipher_parameters(ctx, NULL, NULL, iv) < 0) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "IV init failed");
-		return 0;
-	}
-
-	/*
-	 * At least as I read RFC 5996 section 3.14, if the cipher
-	 * has a block size of which the ciphertext's size must
-	 * be a multiple, the payload must be padded to make that
-	 * happen, so the ciphertext length must be a multiple of
-	 * the block size.  Fail if that's not the case.
-	 */
-	block_size = (unsigned int)EVP_CIPHER_CTX_block_size(ctx);
-	if ((ctlen % block_size) != 0) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "ciphertext size %u is not a multiple of the cipher block size %u",
-		    ctlen, block_size);
-		return 0;
-	}
-
-	/*
-	 * Attempt to allocate a buffer for the decrypted data, because
-	 * we can't decrypt on top of the input buffer.
-	 */
-	ptlen = ctlen;
-	pt = (u_char *)malloc(ptlen);
-	if (pt == NULL) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
-			"can't allocate memory for decryption buffer");
-	}
-
-	/*
-	 * The size of the ciphertext handed to us is a multiple of the
-	 * cipher block size, so we don't need to worry about padding.
-	 */
-	if (!EVP_CIPHER_CTX_set_padding(ctx, 0)) {
-		free(pt);
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "EVP_CIPHER_CTX_set_padding failed");
+	pt = do_decrypt(ndo, "esp_print_decrypt_buffer_by_ikev2", sa, iv,
+	    ct, ctlen);
+	if (pt == NULL)
 		return 0;
-	}
-	if (!EVP_DecryptUpdate(ctx, pt, &len, ct, ctlen)) {
-		free(pt);
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "EVP_DecryptUpdate failed");
-		return 0;
-	}
-	EVP_CIPHER_CTX_free(ctx);
 
 	/*
 	 * Switch to the output buffer for dissection, and save it
@@ -708,13 +736,9 @@ esp_print(netdissect_options *ndo,
 	const struct ip6_hdr *ip6 = NULL;
 	const u_char *iv;
 	u_int ivlen;
+	u_int payloadlen;
 	const u_char *ct;
-	u_int ctlen;
-	int len;
-	EVP_CIPHER_CTX *ctx;
-	unsigned int block_size;
 	u_char *pt;
-	u_int ptlen;
 	u_int padlen;
 	u_int nh;
 #endif
@@ -825,7 +849,7 @@ esp_print(netdissect_options *ndo,
 	 * the beginning of the authentication data/integrity check
 	 * value, i.e. right past the end of the ciphertext;
 	 */
-	ctlen = ep - ct;
+	payloadlen = ep - ct;
 
 	if (sa->evp == NULL)
 		return;
@@ -842,81 +866,15 @@ esp_print(netdissect_options *ndo,
 		return;
 	}
 
-	ctx = EVP_CIPHER_CTX_new();
-	if (ctx == NULL) {
-		/*
-		 * Failed to initialize the cipher context.
-		 * From a look at the OpenSSL code, this appears to
-		 * mean "couldn't allocate memory for the cipher context";
-		 * note that we're not passing any parameters, so there's
-		 * not much else it can mean.
-		 */
-		(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
-			"esp_print: can't allocate memory for cipher context");
-	}
-
-	if (set_cipher_parameters(ctx, sa->evp, sa->secret, NULL) < 0) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "espkey init failed");
-		return;
-	}
-
-	if (set_cipher_parameters(ctx, NULL, NULL, iv) < 0) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "IV init failed");
+	pt = do_decrypt(ndo, "esp_print", sa, iv, ct, payloadlen);
+	if (pt == NULL)
 		return;
-	}
-
-	/*
-	 * At least as I read RFC 4303 section 2.4, if the cipher
-	 * has a block size of which the ciphertext's size must
-	 * be a multiple, the payload must be padded to make that
-	 * happen, so the ciphertext length must be a multiple of
-	 * the block size.  Fail if that's not the case.
-	 */
-	block_size = (unsigned int)EVP_CIPHER_CTX_block_size(ctx);
-	if ((ctlen % block_size) != 0) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "ciphertext size %u is not a multiple of the cipher block size %u",
-		    ctlen, block_size);
-		return;
-	}
-
-	/*
-	 * Attempt to allocate a buffer for the decrypted data, because
-	 * we can't decrypt on top of the input buffer.
-	 */
-	ptlen = ctlen;
-	pt = (u_char *)malloc(ptlen);
-	if (pt == NULL) {
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
-			"esp_print: can't allocate memory for decryption buffer");
-	}
-
-	/*
-	 * The size of the ciphertext handed to us is a multiple of the
-	 * cipher block size, so we don't need to worry about padding.
-	 */
-	if (!EVP_CIPHER_CTX_set_padding(ctx, 0)) {
-		free(pt);
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "EVP_CIPHER_CTX_set_padding failed");
-		return;
-	}
-	if (!EVP_DecryptUpdate(ctx, pt, &len, ct, ctlen)) {
-		free(pt);
-		EVP_CIPHER_CTX_free(ctx);
-		(*ndo->ndo_warning)(ndo, "EVP_DecryptUpdate failed");
-		return;
-	}
-	EVP_CIPHER_CTX_free(ctx);
 
 	/*
 	 * Switch to the output buffer for dissection, and
 	 * save it on the buffer stack so it can be freed.
 	 */
-	ep = pt + ptlen;
+	ep = pt + payloadlen;
 	if (!nd_push_buffer(ndo, pt, pt, ep)) {
 		free(pt);
 		(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
@@ -933,7 +891,7 @@ esp_print(netdissect_options *ndo,
 	 * "plaintext" is not what was being sent.
 	 */
 	padlen = GET_U_1(ep - 2);
-	if (padlen + 2 > ptlen) {
+	if (padlen + 2 > payloadlen) {
 		nd_print_trunc(ndo);
 		return;
 	}
@@ -944,7 +902,7 @@ esp_print(netdissect_options *ndo,
 	ND_PRINT(": ");
 
 	/* Now dissect the plaintext. */
-	ip_print_demux(ndo, pt, ptlen - (padlen + 2), ver, fragmented,
+	ip_print_demux(ndo, pt, payloadlen - (padlen + 2), ver, fragmented,
 	    ttl_hl, nh, bp2);
 
 	/* Pop the buffer, freeing it. */