From: Bastien Roucariès <ro...@debian.org> Clearly document that HOME, LOGNAME, SHELL and USER are set at login time by program like login (1).
Document also that using su could result in a mixed environment, and point to su manual. Signed-off-by: Bastien Roucariès <ro...@debian.org> --- man7/environ.7 | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-) diff --git a/man7/environ.7 b/man7/environ.7 index 8f89ba86b..e33dcc754 100644 --- a/man7/environ.7 +++ b/man7/environ.7 @@ -65,15 +65,15 @@ Common examples are: .TP .B USER The name of the logged-in user (used by some BSD-derived programs). +Set at login time, see section NOTES below. .TP .B LOGNAME The name of the logged-in user (used by some System-V derived programs). +Set at login time, see section NOTES below. .TP .B HOME -A user's login directory, set by -.BR login (1) -from the password file -.BR passwd (5). +A user's login directory, set a login time. +Set at login time, see section NOTES below. .TP .B LANG The name of a locale to use for locale categories when not overridden @@ -114,6 +114,7 @@ Set by some shells. .TP .B SHELL The absolute pathname of the user's login shell. +Set at login time, see section NOTES below. .TP .B TERM The terminal type for which output is to be prepared. @@ -260,6 +261,30 @@ The and .B PR_SET_MM_ENV_END operations can be used to control the location of the process's environment. +.PP +The +.B HOME, +.B LOGNAME, +.B SHELL +and +.B USER +variables are only set when an user is changing using +session management interface, typically by program +.B login(1) +from user database (for instance, but not limited, by using +.B password (5) +database). +Particularly, +.BR setuid (2) +family of function +does not set theses variables. Notes that as documented, +going to root by +.BR su (8) +may result in a mixed environment where +.B LOGNAME +and +.B USER +are retained from old user. .SH BUGS Clearly there is a security risk here. Many a system command has been @@ -305,6 +330,7 @@ should consider renaming their option to .BR login (1), .BR printenv (1), .BR sh (1), +.BR su (1), .BR tcsh (1), .BR execve (2), .BR clearenv (3), -- 2.29.2
