From fa52ac9781f479de8ab4d8526276244c0a0471f4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?S=C3=B6ren=20Tempel?= Date: Mon, 28 Feb 2022 08:36:50 +0100 Subject: [PATCH] ash: don't read past end of var in subvareval for bash substitutions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Without this patch, BusyBox handles bash pattern substitutions without a terminating '/' character incorrectly. Consider the following shell script: _bootstrapver=5.0.211-r0 _referencesdir="/usr/${_bootstrapver/-*}/Sources" echo $_referencesdir This should output `/usr/5.0.211/Sources`. However, without this patch it instead outputs `/usr/5.0.211Sources`. This is due to the fact that BusyBox expects the bash pattern substitutions to always be terminated with a '/' (at least in this part of subvareval) and thus reads passed the substitution itself and consumes the '/' character which is part of the literal string. If there is no '/' after the substitution then BusyBox might perform an out-of-bounds read under certain circumstances. When replacing the bash pattern substitution with `${_bootstrapver/-*/}`, or with this patch applied, ash outputs the correct value. Signed-off-by: Sören Tempel Signed-off-by: Denys Vlasenko --- shell/ash.c | 4 ++++ shell/ash_test/ash-vars/var_bash_repl_unterminated.right | 1 + shell/ash_test/ash-vars/var_bash_repl_unterminated.tests | 2 ++ shell/hush_test/hush-vars/var_bash_repl_unterminated.right | 1 + shell/hush_test/hush-vars/var_bash_repl_unterminated.tests | 2 ++ 5 files changed, 10 insertions(+) create mode 100644 shell/ash_test/ash-vars/var_bash_repl_unterminated.right create mode 100755 shell/ash_test/ash-vars/var_bash_repl_unterminated.tests create mode 100644 shell/hush_test/hush-vars/var_bash_repl_unterminated.right create mode 100755 shell/hush_test/hush-vars/var_bash_repl_unterminated.tests diff --git a/shell/ash.c b/shell/ash.c index adb0f223a..54335c5dd 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -7081,6 +7081,10 @@ subevalvar(char *start, char *str, int strloc, *repl = '\0'; break; } + if ((unsigned char)*repl == CTLENDVAR) { /* ${v/pattern} (no trailing /, no repl) */ + repl = NULL; + break; + } /* Handle escaped slashes, e.g. "${v/\//_}" (they are CTLESC'ed by this point) */ if ((unsigned char)*repl == CTLESC && repl[1]) repl++; diff --git a/shell/ash_test/ash-vars/var_bash_repl_unterminated.right b/shell/ash_test/ash-vars/var_bash_repl_unterminated.right new file mode 100644 index 000000000..5bff3a6fa --- /dev/null +++ b/shell/ash_test/ash-vars/var_bash_repl_unterminated.right @@ -0,0 +1 @@ +b/d diff --git a/shell/ash_test/ash-vars/var_bash_repl_unterminated.tests b/shell/ash_test/ash-vars/var_bash_repl_unterminated.tests new file mode 100755 index 000000000..c9513343d --- /dev/null +++ b/shell/ash_test/ash-vars/var_bash_repl_unterminated.tests @@ -0,0 +1,2 @@ +a=b-c +echo ${a/-*}/d diff --git a/shell/hush_test/hush-vars/var_bash_repl_unterminated.right b/shell/hush_test/hush-vars/var_bash_repl_unterminated.right new file mode 100644 index 000000000..5bff3a6fa --- /dev/null +++ b/shell/hush_test/hush-vars/var_bash_repl_unterminated.right @@ -0,0 +1 @@ +b/d diff --git a/shell/hush_test/hush-vars/var_bash_repl_unterminated.tests b/shell/hush_test/hush-vars/var_bash_repl_unterminated.tests new file mode 100755 index 000000000..c9513343d --- /dev/null +++ b/shell/hush_test/hush-vars/var_bash_repl_unterminated.tests @@ -0,0 +1,2 @@ +a=b-c +echo ${a/-*}/d