lib-dcrypt: Fixed accessing out-of-bounds data in istream.

Also some small cleanups to make it clearer what's actually happening.

diff --git a/src/lib-dcrypt/istream-decrypt.c b/src/lib-dcrypt/istream-decrypt.c
index a514b24d7d9c977975fca825c68fc03594f2844d..c5807c2436d5a551717115d3da7fdc31fcc990d3 100644 (file)
--- a/src/lib-dcrypt/istream-decrypt.c
+++ b/src/lib-dcrypt/istream-decrypt.c
@@ -54,13 +54,13 @@ ssize_t i_stream_decrypt_read_header_v1(struct decrypt_istream *stream,
        const unsigned char *data, size_t mlen)
 {
        const char *error = NULL;
-       size_t hdr_len = 0;
+       size_t keydata_len = 0;
        uint16_t len;
        int ec, i = 0;
 
        const unsigned char *digest_pos = NULL, *key_digest_pos = NULL, *key_ct_pos = NULL;
 
-       size_t pos = 9;
+       size_t pos = sizeof(IOSTREAM_CRYPT_MAGIC);
        size_t digest_len = 0;
        size_t key_ct_len = 0;
        size_t key_digest_size = 0;
@@ -69,9 +69,10 @@ ssize_t i_stream_decrypt_read_header_v1(struct decrypt_istream *stream,
        buffer_t *secret = buffer_create_dynamic(pool_datastack_create(), 256);
        buffer_t *key = buffer_create_dynamic(pool_datastack_create(), 256);
 
-       hdr_len = ((data[0] << 8) | data[1]) + 12;
-
-       if (mlen < hdr_len - pos) {
+       if (mlen < 2)
+               return 0;
+       keydata_len = (data[0] << 8) | data[1];
+       if (mlen-2 < keydata_len) {
                /* try to read more */
                return 0;
        }
@@ -79,12 +80,14 @@ ssize_t i_stream_decrypt_read_header_v1(struct decrypt_istream *stream,
        data+=2;
        mlen-=2;
 
-       memcpy(&len, data, 2);
-
-       while(i < 4 && mlen > 2 && (len = ntohs(len)) <= (mlen - 2) && len > 0) {
+       while (i < 4 && mlen > 2) {
+               memcpy(&len, data, 2);
+               len = ntohs(len);
                data += 2;
                mlen -= 2;
                pos += 2;
+               if (len == 0 || len > mlen)
+                       break;
 
                switch(i++) {
                case 0:
@@ -109,7 +112,6 @@ ssize_t i_stream_decrypt_read_header_v1(struct decrypt_istream *stream,
                pos += len;
                data += len;
                mlen -= len;
-               memcpy(&len, data, 2);
        }
 
        if (i < 4) {
@@ -227,7 +229,7 @@ ssize_t i_stream_decrypt_read_header_v1(struct decrypt_istream *stream,
        stream->initialized = TRUE;
        /* now we are ready to decrypt stream */
 
-       return hdr_len;
+       return sizeof(IOSTREAM_CRYPT_MAGIC) + 1 + 2 + keydata_len;
 }
 
 static bool get_msb32(const unsigned char **_data, const unsigned char *end, uint32_t *num_r)

diff --git a/src/lib-dcrypt/ostream-encrypt.c b/src/lib-dcrypt/ostream-encrypt.c
index 84919d32d82a74be8ddb97beb81f1d8155fb05e2..ae661a9e7316e8e8f4c005298cac0885b2c935a0 100644 (file)
--- a/src/lib-dcrypt/ostream-encrypt.c
+++ b/src/lib-dcrypt/ostream-encrypt.c
@@ -84,7 +84,7 @@ int o_stream_encrypt_send_header_v1(struct encrypt_ostream *stream)
        /* version */
        c = 1;
        buffer_append(values, &c, 1);
-       /* header length including this and data written so far */
+       /* key data length */
        s = htons(stream->key_data_len);
        buffer_append(values, &s, 2);
        /* then write key data */