init: Refuse to import $KSH_VERSION from environment

McDutchie · McDutchie · commit 86fc4c6d0ac3 · 2021-01-08T21:59:30.000Z
$KSH_VERSION is initialised as a nameref to ${.sh.version}, but it was not realiable as it could be overridden from the environment. Some scripts do version checking so this would allow influencing their execution. This fix is inspired by the following Solaris patch: https://github.com/oracle/solaris-userland/blob/master/components/ksh93/patches/200-17435456.patch but a different approach was needed, because the code has changed (see 960a1a9). src/cmd/ksh93/sh/init.c: env_init(): - Refuse to import $KSH_VERSION. Using strncmp(3) might be crude, but it's effective and I can't figure out another way.
diff --git a/src/cmd/ksh93/sh/init.c b/src/cmd/ksh93/sh/init.c
@@ -1911,6 +1911,8 @@ static char *env_init(Shell_t *shp)
 			/* The magic A__z env var is an invention of ksh88. See e_envmarker[]. */
 			if(*cp=='A' && cp[1]=='_' && cp[2]=='_' && cp[3]=='z' && cp[4]=='=')
 				next = cp + 4;
+			else if(strncmp(cp,"KSH_VERSION=",12)==0)
+				continue;
 			else if(np = nv_open(cp,shp->var_tree,(NV_EXPORT|NV_IDENT|NV_ASSIGN|NV_NOFAIL)))
 			{
 				nv_onattr(np,NV_IMPORT);

Original file line number	Diff line number	Diff line change
`@@ -1911,6 +1911,8 @@ static char env_init(Shell_t shp)`
`1911`	`1911`	`/* The magic A__z env var is an invention of ksh88. See e_envmarker[]. */`
`1912`	`1912`	`if(*cp=='A' && cp[1]=='_' && cp[2]=='_' && cp[3]=='z' && cp[4]=='=')`
`1913`	`1913`	`next = cp + 4;`
	`1914`	`+ else if(strncmp(cp,"KSH_VERSION=",12)==0)`
	`1915`	`+ continue;`
`1914`	`1916`	`else if(np = nv_open(cp,shp->var_tree,(NV_EXPORT\|NV_IDENT\|NV_ASSIGN\|NV_NOFAIL)))`
`1915`	`1917`	`{`
`1916`	`1918`	`nv_onattr(np,NV_IMPORT);`