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Uids should not be allowed to set to negative

PATCH Applied Cai Xianchao 3 participants 5 messages Aug 8, 2008 – Aug 12, 2008

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Cai Xianchao

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#0 lore raw

PATCH 1/1 Uids should not be allowed to set to negative

Hello Steve,

When I tried to set uid to negative, no error message was outputed and the return value was 0. In the rule list, the value of uid was also negative. Negative uid does not exist and the negative user can't be added. So, I think uids can't be set to negative.

It is also strange that gid can't be set to negative, while uid can.

I did as follows:
#auditctl -a exit,always -F uid=-1
#auditctl -l
LIST_RULES: exit,always uid=-1 (0xffffffff) syscall=all

Signed-off-by Cai Xianchao <[email protected]>

---

deprecated.c +0 -4
index 6bf42dd..94954a5 100644
@@ -257,10 +257,6 @@ int audit_rule_fieldpair(struct audit_rule *rule, const char *pair, int flags)
 			if (isdigit((char)*(v))) 
 				rule->values[rule->field_count] = 
 					strtol(v, NULL, 0);
-			else if (vlen >= 2 && *(v)=='-' && 
-						(isdigit((char)*(v+1)))) 
-				rule->values[rule->field_count] = 
-					strtol(v, NULL, 0);
 			else {
 				if (name_to_uid(v, 
 					&rule->values[rule->field_count])) {
libaudit.c +0 -4
index 7d48d78..85adbc5 100644
@@ -850,10 +850,6 @@ int audit_rule_fieldpair_data(struct audit_rule_data **rulep, const char *pair,
 			if (isdigit((char)*(v))) 
 				rule->values[rule->field_count] = 
 					strtol(v, NULL, 0);
-			else if (vlen >= 2 && *(v)=='-' && 
-						(isdigit((char)*(v+1)))) 
-				rule->values[rule->field_count] = 
-					strtol(v, NULL, 0);
 			else {
 				if (audit_name_to_uid(v, 
 					&rule->values[rule->field_count])) {
#1 lore raw
Quoted 8 lines · Cai Xianchao

Hello Steve,

When I tried to set uid to negative, no error message was outputed and the return value was 0. In the rule list, the value of uid was also negative. Negative uid does not exist and the negative user can't be added. So, I think uids can't be set to negative.

It is also strange that gid can't be set to negative, while uid can.

Its not the same code that matches uid and auid is it? auid can reasonably be negative for anything that wasn't done from a login shell. just want to make sure you don't lose that ability.

-Eric

Quoted 43 lines

I did as follows:
#auditctl -a exit,always -F uid=-1
#auditctl -l
LIST_RULES: exit,always uid=-1 (0xffffffff) syscall=all

Signed-off-by Cai Xianchao <[email protected]>

---

deprecated.c +0 -4
index 6bf42dd..94954a5 100644
@@ -257,10 +257,6 @@ int audit_rule_fieldpair(struct audit_rule *rule, const char *pair, int flags)
 			if (isdigit((char)*(v))) 
 				rule->values[rule->field_count] = 
 					strtol(v, NULL, 0);
-			else if (vlen >= 2 && *(v)=='-' && 
-						(isdigit((char)*(v+1)))) 
-				rule->values[rule->field_count] = 
-					strtol(v, NULL, 0);
 			else {
 				if (name_to_uid(v, 
 					&rule->values[rule->field_count])) {
libaudit.c +0 -5
index 7d48d78..85adbc5 100644
@@ -850,10 +850,6 @@ int audit_rule_fieldpair_data(struct audit_rule_data **rulep, const char *pair,
 			if (isdigit((char)*(v))) 
 				rule->values[rule->field_count] = 
 					strtol(v, NULL, 0);
-			else if (vlen >= 2 && *(v)=='-' && 
-						(isdigit((char)*(v+1)))) 
-				rule->values[rule->field_count] = 
-					strtol(v, NULL, 0);
 			else {
 				if (audit_name_to_uid(v, 
 					&rule->values[rule->field_count])) {
 
--

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#2 lore raw
Quoted 5 lines · On Friday 08 August 2008 09:25:09 Eric Paris wrote:
Quoted 1 line

It is also strange that gid can't be set to negative, while uid can.

Its not the same code that matches uid and auid is it?  auid can reasonably be negative for anything that wasn't done from a login shell. just want to make sure you don't lose that ability.

That's true. But unfortunately, we have to give the uid as the unsigned value or we lose a bit in the conversion and it doesn't match. On second thought, maybe we can't do negative uids from user space because of that conversion to unsigned inside the rule matching engine.

-Steve

#3 lore raw
In reply to Cai Xianchao
Quoted 4 lines · On Friday 08 August 2008 06:09:59 Cai Xianchao wrote:

When I tried to set uid to negative, no error message was outputed and the return value was 0. In the rule list, the value of uid was also negative. Negative uid does not exist and the negative user can't be added. So, I think uids can't be set to negative.

There really is uid -1 and uid -2. We run into this problem with faillog all the time. I think they are nobody and nfsnobody respectively. They used by NFS.

-Steve

Applied
#4 lore raw
In reply to Cai Xianchao
Quoted 4 lines · On Friday 08 August 2008 06:09:59 Cai Xianchao wrote:

When I tried to set uid to negative, no error message was outputed and the return value was 0. In the rule list, the value of uid was also negative. Negative uid does not exist and the negative user can't be added. So, I think uids can't be set to negative.

Applied. Thanks for the patch !

-Steve