Revert bio_prev removal

As schwarze points out, you can pop any BIO in a chain, not just the first
one (bonus points for a great name for this API).

The internal doubly linked was used to fix up the BIO chain bio was part
of when you BIO_pop() a bio that wasn't in the first position, which is
explicitly allowed in our documentation and implied by OpenSSL's.

diff --git a/lib/libcrypto/bio/bio_lib.c b/lib/libcrypto/bio/bio_lib.c
index b33ebe1..c09ad8f 100644 (file)
--- a/lib/libcrypto/bio/bio_lib.c
+++ b/lib/libcrypto/bio/bio_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bio_lib.c,v 1.38 2022/11/30 01:56:18 jsing Exp $ */
+/* $OpenBSD: bio_lib.c,v 1.39 2022/12/02 19:44:04 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -161,6 +161,7 @@ BIO_set(BIO *bio, const BIO_METHOD *method)
        bio->retry_reason = 0;
        bio->num = 0;
        bio->ptr = NULL;
+       bio->prev_bio = NULL;
        bio->next_bio = NULL;
        bio->references = 1;
        bio->num_read = 0L;
@@ -636,6 +637,8 @@ BIO_push(BIO *b, BIO *bio)
        while (lb->next_bio != NULL)
                lb = lb->next_bio;
        lb->next_bio = bio;
+       if (bio != NULL)
+               bio->prev_bio = lb;
        /* called to do internal processing */
        BIO_ctrl(b, BIO_CTRL_PUSH, 0, lb);
        return (b);
@@ -653,7 +656,13 @@ BIO_pop(BIO *b)
 
        BIO_ctrl(b, BIO_CTRL_POP, 0, b);
 
+       if (b->prev_bio != NULL)
+               b->prev_bio->next_bio = b->next_bio;
+       if (b->next_bio != NULL)
+               b->next_bio->prev_bio = b->prev_bio;
+
        b->next_bio = NULL;
+       b->prev_bio = NULL;
        return (ret);
 }
 

diff --git a/lib/libcrypto/bio/bio_local.h b/lib/libcrypto/bio/bio_local.h
index 94dd460..4eecf7e 100644 (file)
--- a/lib/libcrypto/bio/bio_local.h
+++ b/lib/libcrypto/bio/bio_local.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: bio_local.h,v 1.4 2022/11/28 07:50:00 tb Exp $ */
+/* $OpenBSD: bio_local.h,v 1.5 2022/12/02 19:44:04 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -87,6 +87,7 @@ struct bio_st {
        int num;
        void *ptr;
        struct bio_st *next_bio;        /* used by filter BIOs */
+       struct bio_st *prev_bio;        /* used by filter BIOs */
        int references;
        unsigned long num_read;
        unsigned long num_write;