2019-12-12 18:34:55 +00:00
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From f7fb525d762ba42f62f1044f07f38a243980a2ba Mon Sep 17 00:00:00 2001
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2019-05-10 17:50:56 +00:00
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From: Greg Hudson <ghudson@mit.edu>
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Date: Sun, 5 May 2019 18:53:27 -0400
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Subject: [PATCH] Simplify SAM-2 as_key handling
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The ctx->gak_fct() call in sam2_process() used an empty salt instead
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of the default salt when the KDC did not supply an explicit salt.
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This bug arose when commit bc096a77ffdab283d77c2e0fc1fdd15b9f77eb41
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changed the internal contracts around salts but did not adjust the
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SAM-2 code. Commit e9aa891fcdb4c08d39902ab89afb268042b60c86 fixed the
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resulting bug, but mistakenly did not adjust the gak_fct call to use
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the correct salt.
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Later on, the code contains a redundant call to krb5_c_string_to_key()
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in the non-USE_SAD_AS_KEY modes, replacing ctx->as_key. This call was
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properly adjusted by commit e9aa891fcdb4c08d39902ab89afb268042b60c86,
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so the improper gak_fct call did not manifest as a bug.
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Fix the gak_fct call to supply the correct salt, and remove the
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redundant string_to_key operation.
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(cherry picked from commit d48670c51460e9a74b4f4a9966f85ca6f77c1d8b)
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---
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src/lib/krb5/krb/preauth_sam2.c | 25 +++----------------------
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1 file changed, 3 insertions(+), 22 deletions(-)
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diff --git a/src/lib/krb5/krb/preauth_sam2.c b/src/lib/krb5/krb/preauth_sam2.c
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index 4c70021a9..c7484c47e 100644
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--- a/src/lib/krb5/krb/preauth_sam2.c
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+++ b/src/lib/krb5/krb/preauth_sam2.c
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@@ -95,7 +95,6 @@ sam2_process(krb5_context context, krb5_clpreauth_moddata moddata,
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krb5_prompt kprompt;
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krb5_prompt_type prompt_type;
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krb5_data defsalt, *salt;
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- struct gak_password *gakpw;
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krb5_checksum **cksum;
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krb5_data *scratch = NULL;
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krb5_boolean valid_cksum = 0;
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@@ -152,9 +151,8 @@ sam2_process(krb5_context context, krb5_clpreauth_moddata moddata,
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salt = ctx->default_salt ? NULL : &ctx->salt;
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retval = ctx->gak_fct(context, request->client, sc2b->sam_etype,
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- prompter, prompter_data, &ctx->salt,
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- &ctx->s2kparams, &ctx->as_key,
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- ctx->gak_data, ctx->rctx.items);
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+ prompter, prompter_data, salt, &ctx->s2kparams,
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+ &ctx->as_key, ctx->gak_data, ctx->rctx.items);
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if (retval) {
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krb5_free_sam_challenge_2(context, sc2);
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krb5_free_sam_challenge_2_body(context, sc2b);
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@@ -212,24 +210,7 @@ sam2_process(krb5_context context, krb5_clpreauth_moddata moddata,
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/* Get encryption key to be used for checksum and sam_response */
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if (!(sc2b->sam_flags & KRB5_SAM_USE_SAD_AS_KEY)) {
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- /* as_key = string_to_key(password) */
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-
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- if (ctx->as_key.length) {
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- krb5_free_keyblock_contents(context, &ctx->as_key);
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- ctx->as_key.length = 0;
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- }
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-
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- /* generate a key using the supplied password */
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- gakpw = ctx->gak_data;
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- retval = krb5_c_string_to_key(context, sc2b->sam_etype,
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- gakpw->password, salt, &ctx->as_key);
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-
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- if (retval) {
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- krb5_free_sam_challenge_2(context, sc2);
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- krb5_free_sam_challenge_2_body(context, sc2b);
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- if (defsalt.length) free(defsalt.data);
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- return(retval);
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- }
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+ /* Retain as_key from above gak_fct call. */
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if (!(sc2b->sam_flags & KRB5_SAM_SEND_ENCRYPTED_SAD)) {
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/* as_key = combine_key (as_key, string_to_key(SAD)) */
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