Mercurial > dropbear
view libtomcrypt/src/misc/adler32.c @ 1788:1fc0012b9c38
Fix handling of replies to global requests (#112)
The current code assumes that all global requests want / need a reply.
This isn't always true and the request itself indicates if it wants a
reply or not.
It causes a specific problem with [email protected] messages.
These are sent by OpenSSH after authentication to inform the client of
potential other host keys for the host. This can be used to add a new
type of host key or to rotate host keys.
The initial information message from the server is sent as a global
request, but with want_reply set to false. This means that the server
doesn't expect an answer to this message. Instead the client needs to
send a prove request as a reply if it wants to receive proof of
ownership for the host keys.
The bug doesn't cause any current problems with due to how OpenSSH
treats receiving the failure message. It instead treats it as a
keepalive message and further ignores it.
Arguably this is a protocol violation though of Dropbear and it is only
accidental that it doesn't cause a problem with OpenSSH.
The bug was found when adding host keys support to libssh, which is more
strict protocol wise and treats the unexpected failure message an error,
also see https://gitlab.com/libssh/libssh-mirror/-/merge_requests/145
for more information.
The fix here is to honor the want_reply flag in the global request and
to only send a reply if the other side expects a reply.
author | Dirkjan Bussink <d.bussink@gmail.com> |
---|---|
date | Thu, 10 Dec 2020 16:13:13 +0100 |
parents | 6dba84798cd5 |
children |
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. */ #include "tomcrypt.h" /** @file adler32.c Adler-32 checksum algorithm Written and placed in the public domain by Wei Dai Adapted for libtomcrypt by Steffen Jaeckel */ #ifdef LTC_ADLER32 static const unsigned long _adler32_base = 65521; void adler32_init(adler32_state *ctx) { LTC_ARGCHKVD(ctx != NULL); ctx->s[0] = 1; ctx->s[1] = 0; } void adler32_update(adler32_state *ctx, const unsigned char *input, unsigned long length) { unsigned long s1, s2; LTC_ARGCHKVD(ctx != NULL); LTC_ARGCHKVD(input != NULL); s1 = ctx->s[0]; s2 = ctx->s[1]; if (length % 8 != 0) { do { s1 += *input++; s2 += s1; length--; } while (length % 8 != 0); if (s1 >= _adler32_base) s1 -= _adler32_base; s2 %= _adler32_base; } while (length > 0) { s1 += input[0]; s2 += s1; s1 += input[1]; s2 += s1; s1 += input[2]; s2 += s1; s1 += input[3]; s2 += s1; s1 += input[4]; s2 += s1; s1 += input[5]; s2 += s1; s1 += input[6]; s2 += s1; s1 += input[7]; s2 += s1; length -= 8; input += 8; if (s1 >= _adler32_base) s1 -= _adler32_base; s2 %= _adler32_base; } LTC_ARGCHKVD(s1 < _adler32_base); LTC_ARGCHKVD(s2 < _adler32_base); ctx->s[0] = (unsigned short)s1; ctx->s[1] = (unsigned short)s2; } void adler32_finish(adler32_state *ctx, void *hash, unsigned long size) { unsigned char* h; LTC_ARGCHKVD(ctx != NULL); LTC_ARGCHKVD(hash != NULL); h = hash; switch (size) { default: h[3] = ctx->s[0] & 0x0ff; /* FALLTHROUGH */ case 3: h[2] = (ctx->s[0] >> 8) & 0x0ff; /* FALLTHROUGH */ case 2: h[1] = ctx->s[1] & 0x0ff; /* FALLTHROUGH */ case 1: h[0] = (ctx->s[1] >> 8) & 0x0ff; /* FALLTHROUGH */ case 0: ; } } int adler32_test(void) { #ifndef LTC_TEST return CRYPT_NOP; #else const void* in = "libtomcrypt"; const unsigned char adler32[] = { 0x1b, 0xe8, 0x04, 0xba }; unsigned char out[4]; adler32_state ctx; adler32_init(&ctx); adler32_update(&ctx, in, strlen(in)); adler32_finish(&ctx, out, 4); if (compare_testvector(adler32, 4, out, 4, "adler32", 0)) { return CRYPT_FAIL_TESTVECTOR; } return CRYPT_OK; #endif } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */