patch 9.0.1481: decrypting with libsodium may fail if the library changes
Problem: Decrypting with libsodium may fail if the library changes.
Solution: Add parameters used to the encrypted file header. (Christian
Brabandt, closes #12279)
diff --git a/src/fileio.c b/src/fileio.c
index 1966420..8d3e6f5 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -218,6 +218,9 @@
int using_b_fname;
static char *msg_is_a_directory = N_("is a directory");
int eof;
+#ifdef FEAT_SODIUM
+ int may_need_lseek = FALSE;
+#endif
au_did_filetype = FALSE; // reset before triggering any autocommands
@@ -1282,15 +1285,43 @@
*/
# ifdef FEAT_SODIUM
// Let the crypt layer work with a buffer size of 8192
+ //
+ // Sodium encryption requires a fixed block size to
+ // successfully decrypt. However, unfortunately the file
+ // header size changes between xchacha20 and xchacha20v2 by
+ // 'add_len' bytes.
+ // So we will now read the maximum header size + encryption
+ // metadata, but after determining to read an xchacha20
+ // encrypted file, we have to rewind the file descriptor by
+ // 'add_len' bytes in the second round.
+ //
+ // Be careful with changing it, it needs to stay the same
+ // for reading back previously encrypted files!
if (filesize == 0)
+ {
// set size to 8K + Sodium Crypt Metadata
size = WRITEBUFSIZE + crypt_get_max_header_len()
+ crypto_secretstream_xchacha20poly1305_HEADERBYTES
+ crypto_secretstream_xchacha20poly1305_ABYTES;
+ may_need_lseek = TRUE;
+ }
- else if (filesize > 0 && (curbuf->b_cryptstate != NULL &&
- curbuf->b_cryptstate->method_nr == CRYPT_M_SOD))
+ else if (filesize > 0 && (curbuf->b_cryptstate != NULL
+ && crypt_method_is_sodium(
+ curbuf->b_cryptstate->method_nr)))
+ {
size = WRITEBUFSIZE + crypto_secretstream_xchacha20poly1305_ABYTES;
+ // need to rewind by - add_len from CRYPT_M_SOD2 (see
+ // description above)
+ if (curbuf->b_cryptstate->method_nr == CRYPT_M_SOD
+ && !eof && may_need_lseek)
+ {
+ lseek(fd, crypt_get_header_len(
+ curbuf->b_cryptstate->method_nr)
+ - crypt_get_max_header_len(), SEEK_CUR);
+ may_need_lseek = FALSE;
+ }
+ }
# endif
eof = size;
size = read_eintr(fd, ptr, size);