bug with SGN_ALG_MD2_5 case handling in kg_unseal_v1()?

[Will Fiveash]

In src/lib/gssapi/krb5/k5unseal.c:kg_unseal_v1() at line 381 which is
part of the case SGN_ALG_MD2_5 block I see:

code = k5_bcmp(md5cksum.contents, ptr + 14, 8);
/* Falls through to defective-token?? */

default:
*minor_status = 0;
return(GSS_S_DEFECTIVE_TOKEN);

This seems like a bug given the processing that precedes this, thoughts?

[Benjamin Kaduk]

Post by Will Fiveash
In src/lib/gssapi/krb5/k5unseal.c:kg_unseal_v1() at line 381 which is
code = k5_bcmp(md5cksum.contents, ptr + 14, 8);
/* Falls through to defective-token?? */
*minor_status = 0;
return(GSS_S_DEFECTIVE_TOKEN);
This seems like a bug given the processing that precedes this, thoughts?

Perhaps. On the other hand, how much do you trust anything with MD2
in its name...

-Ben
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[Will Fiveash]

Post by Benjamin Kaduk

Post by Will Fiveash
In src/lib/gssapi/krb5/k5unseal.c:kg_unseal_v1() at line 381 which is
code = k5_bcmp(md5cksum.contents, ptr + 14, 8);
/* Falls through to defective-token?? */
*minor_status = 0;
return(GSS_S_DEFECTIVE_TOKEN);
This seems like a bug given the processing that precedes this, thoughts?

Perhaps. On the other hand, how much do you trust anything with MD2
in its name...

Indeed.

[Greg Hudson]

Post by Will Fiveash
In src/lib/gssapi/krb5/k5unseal.c:kg_unseal_v1() at line 381 which is
code = k5_bcmp(md5cksum.contents, ptr + 14, 8);
/* Falls through to defective-token?? */
*minor_status = 0;
return(GSS_S_DEFECTIVE_TOKEN);
This seems like a bug given the processing that precedes this, thoughts?

It does look like a bug. The code's been like that since 1.0; the
comment was added in 1.2. It would seem that unwrapping tokens using
SGN_ALG_MD2_5 never worked, and we could probably get rid of the code.
Neither our code nor Heimdal's appears to choose SGN_ALG_MD2_5 when
creating tokens, by my reading.

(According to RFC 1964, "MD2.5" refers to using half of the 128-bit MD5
checksum; it doesn't actually reference the MD2 hash algorithm.)
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krbdev mailing list ***@mit.edu
https://mailman.mit.edu/mailman/listinfo/krbdev

[Will Fiveash]

Post by Greg Hudson

Post by Will Fiveash
In src/lib/gssapi/krb5/k5unseal.c:kg_unseal_v1() at line 381 which is
code = k5_bcmp(md5cksum.contents, ptr + 14, 8);
/* Falls through to defective-token?? */
*minor_status = 0;
return(GSS_S_DEFECTIVE_TOKEN);
This seems like a bug given the processing that precedes this, thoughts?

It does look like a bug. The code's been like that since 1.0; the
comment was added in 1.2. It would seem that unwrapping tokens using
SGN_ALG_MD2_5 never worked, and we could probably get rid of the code.
Neither our code nor Heimdal's appears to choose SGN_ALG_MD2_5 when
creating tokens, by my reading.
(According to RFC 1964, "MD2.5" refers to using half of the 128-bit MD5
checksum; it doesn't actually reference the MD2 hash algorithm.)

It would be good to delete that code as it was flagged during recent
code checking for improper case fall-throughs.