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92eb6c3060
Commit3f69cc6076("crypto: af_alg - Allow arbitrarily long algorithm names") made the kernel start accepting arbitrarily long algorithm names in sockaddr_alg. However, the actual length of the salg_name field stayed at the original 64 bytes. This is broken because the kernel can access indices >= 64 in salg_name, which is undefined behavior -- even though the memory that is accessed is still located within the sockaddr structure. It would only be defined behavior if the array were properly marked as arbitrary-length (either by making it a flexible array, which is the recommended way these days, or by making it an array of length 0 or 1). We can't simply change salg_name into a flexible array, since that would break source compatibility with userspace programs that embed sockaddr_alg into another struct, or (more commonly) declare a sockaddr_alg like 'struct sockaddr_alg sa = { .salg_name = "foo" };'. One solution would be to change salg_name into a flexible array only when '#ifdef __KERNEL__'. However, that would keep userspace without an easy way to actually use the longer algorithm names. Instead, add a new structure 'sockaddr_alg_new' that has the flexible array field, and expose it to both userspace and the kernel. Make the kernel use it correctly in alg_bind(). This addresses the syzbot report "UBSAN: array-index-out-of-bounds in alg_bind" (https://syzkaller.appspot.com/bug?extid=92ead4eb8e26a26d465e). Reported-by: syzbot+92ead4eb8e26a26d465e@syzkaller.appspotmail.com Fixes:3f69cc6076("crypto: af_alg - Allow arbitrarily long algorithm names") Cc: <stable@vger.kernel.org> # v4.12+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
60 lines
1.5 KiB
C
60 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
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/*
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* if_alg: User-space algorithm interface
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*
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* Copyright (c) 2010 Herbert Xu <herbert@gondor.apana.org.au>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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*/
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#ifndef _LINUX_IF_ALG_H
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#define _LINUX_IF_ALG_H
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#include <linux/types.h>
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struct sockaddr_alg {
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__u16 salg_family;
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__u8 salg_type[14];
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__u32 salg_feat;
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__u32 salg_mask;
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__u8 salg_name[64];
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};
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/*
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* Linux v4.12 and later removed the 64-byte limit on salg_name[]; it's now an
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* arbitrary-length field. We had to keep the original struct above for source
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* compatibility with existing userspace programs, though. Use the new struct
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* below if support for very long algorithm names is needed. To do this,
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* allocate 'sizeof(struct sockaddr_alg_new) + strlen(algname) + 1' bytes, and
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* copy algname (including the null terminator) into salg_name.
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*/
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struct sockaddr_alg_new {
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__u16 salg_family;
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__u8 salg_type[14];
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__u32 salg_feat;
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__u32 salg_mask;
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__u8 salg_name[];
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};
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struct af_alg_iv {
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__u32 ivlen;
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__u8 iv[0];
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};
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/* Socket options */
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#define ALG_SET_KEY 1
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#define ALG_SET_IV 2
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#define ALG_SET_OP 3
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#define ALG_SET_AEAD_ASSOCLEN 4
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#define ALG_SET_AEAD_AUTHSIZE 5
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#define ALG_SET_DRBG_ENTROPY 6
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/* Operations */
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#define ALG_OP_DECRYPT 0
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#define ALG_OP_ENCRYPT 1
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#endif /* _LINUX_IF_ALG_H */
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