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login(1): when exporting variables check the result of setenv(3)

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When exporting a variable we correctly check all the preconditions that
could make setenv(3) fail. Checking the setenv(3) return value seems
redundant, but given that login(1) is critical, it doesn't hurt to have
a post-check.

This change is based on the "Principles of Secure Coding" course by
Matthew Bishop, PhD., which specifically discusses this code in FreeBSD.

(This change redoes r368776 due to a silly mistake)
This commit is contained in:
Pedro F. Giffuni 2020-12-19 03:07:38 +00:00
parent a0bed90198
commit dcc6f62526
1 changed files with 4 additions and 1 deletions
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5
usr.bin/login/login.c
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@ -793,6 +793,7 @@ export(const char *s)
char *p;
const char **pp;
size_t n;
int rv;
if (strlen(s) > 1024 || (p = strchr(s, '=')) == NULL)
return (0);
@ -804,8 +805,10 @@ export(const char *s)
return (0);
}
*p = '\0';
(void)setenv(s, p + 1, 1);
rv = setenv(s, p + 1, 1);
*p = '=';
if (rv == -1)
return (0);
return (1);
}