Merge branch 'rh/prompt-pcmode-avoid-eval-on-refname' into maint

The shell prompt script (in contrib/), when using the PROMPT_COMMAND
interface, used an unsafe construct when showing the branch name in
$PS1.

* rh/prompt-pcmode-avoid-eval-on-refname:
  git-prompt.sh: don't put unsanitized branch names in $PS1

2 files changed, 54 insertions, 24 deletions

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 7b732d2ae..bd7ff291b 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -207,7 +207,18 @@ __git_ps1_show_upstream ()
 			p=" u+${count#*	}-${count%	*}" ;;
 		esac
 		if [[ -n "$count" && -n "$name" ]]; then
-			p="$p $(git rev-parse --abbrev-ref "$upstream" 2>/dev/null)"
+			__git_ps1_upstream_name=$(git rev-parse \
+				--abbrev-ref "$upstream" 2>/dev/null)
+			if [ $pcmode = yes ]; then
+				# see the comments around the
+				# __git_ps1_branch_name variable below
+				p="$p \${__git_ps1_upstream_name}"
+			else
+				p="$p ${__git_ps1_upstream_name}"
+				# not needed anymore; keep user's
+				# environment clean
+				unset __git_ps1_upstream_name
+			fi
 		fi
 	fi
 
@@ -438,8 +449,27 @@ __git_ps1 ()
 		__git_ps1_colorize_gitstring
 	fi
 
+	b=${b##refs/heads/}
+	if [ $pcmode = yes ]; then
+		# In pcmode (and only pcmode) the contents of
+		# $gitstring are subject to expansion by the shell.
+		# Avoid putting the raw ref name in the prompt to
+		# protect the user from arbitrary code execution via
+		# specially crafted ref names (e.g., a ref named
+		# '$(IFS=_;cmd=sudo_rm_-rf_/;$cmd)' would execute
+		# 'sudo rm -rf /' when the prompt is drawn).  Instead,
+		# put the ref name in a new global variable (in the
+		# __git_ps1_* namespace to avoid colliding with the
+		# user's environment) and reference that variable from
+		# PS1.
+		__git_ps1_branch_name=$b
+		# note that the $ is escaped -- the variable will be
+		# expanded later (when it's time to draw the prompt)
+		b="\${__git_ps1_branch_name}"
+	fi
+
 	local f="$w$i$s$u"
-	local gitstring="$c${b##refs/heads/}${f:+$z$f}$r$p"
+	local gitstring="$c$b${f:+$z$f}$r$p"
 
 	if [ $pcmode = yes ]; then
 		if [ "${__git_printf_supports_v-}" != yes ]; then
diff --git a/t/t9903-bash-prompt.sh b/t/t9903-bash-prompt.sh
index 59f875e83..6efd0d9c7 100755
--- a/t/t9903-bash-prompt.sh
+++ b/t/t9903-bash-prompt.sh
@@ -452,53 +452,53 @@ test_expect_success 'prompt - format string starting with dash' '
 '
 
 test_expect_success 'prompt - pc mode' '
-	printf "BEFORE: (master):AFTER" >expected &&
+	printf "BEFORE: (\${__git_ps1_branch_name}):AFTER\\nmaster" >expected &&
 	printf "" >expected_output &&
 	(
 		__git_ps1 "BEFORE:" ":AFTER" >"$actual" &&
 		test_cmp expected_output "$actual" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - branch name' '
-	printf "BEFORE: (${c_green}master${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear}):AFTER\\nmaster" >expected &&
 	(
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		__git_ps1 "BEFORE:" ":AFTER" >"$actual"
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - detached head' '
-	printf "BEFORE: (${c_red}(%s...)${c_clear}):AFTER" $(git log -1 --format="%h" b1^) >expected &&
+	printf "BEFORE: (${c_red}\${__git_ps1_branch_name}${c_clear}):AFTER\\n(%s...)" $(git log -1 --format="%h" b1^) >expected &&
 	git checkout b1^ &&
 	test_when_finished "git checkout master" &&
 	(
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - dirty status indicator - dirty worktree' '
-	printf "BEFORE: (${c_green}master${c_clear} ${c_red}*${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear} ${c_red}*${c_clear}):AFTER\\nmaster" >expected &&
 	echo "dirty" >file &&
 	test_when_finished "git reset --hard" &&
 	(
 		GIT_PS1_SHOWDIRTYSTATE=y &&
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - dirty status indicator - dirty index' '
-	printf "BEFORE: (${c_green}master${c_clear} ${c_green}+${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear} ${c_green}+${c_clear}):AFTER\\nmaster" >expected &&
 	echo "dirty" >file &&
 	test_when_finished "git reset --hard" &&
 	git add -u &&
@@ -506,13 +506,13 @@ test_expect_success 'prompt - bash color pc mode - dirty status indicator - dirt
 		GIT_PS1_SHOWDIRTYSTATE=y &&
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - dirty status indicator - dirty index and worktree' '
-	printf "BEFORE: (${c_green}master${c_clear} ${c_red}*${c_green}+${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear} ${c_red}*${c_green}+${c_clear}):AFTER\\nmaster" >expected &&
 	echo "dirty index" >file &&
 	test_when_finished "git reset --hard" &&
 	git add -u &&
@@ -521,25 +521,25 @@ test_expect_success 'prompt - bash color pc mode - dirty status indicator - dirt
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		GIT_PS1_SHOWDIRTYSTATE=y &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - dirty status indicator - before root commit' '
-	printf "BEFORE: (${c_green}master${c_clear} ${c_green}#${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear} ${c_green}#${c_clear}):AFTER\\nmaster" >expected &&
 	(
 		GIT_PS1_SHOWDIRTYSTATE=y &&
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		cd otherrepo &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - inside .git directory' '
-	printf "BEFORE: (${c_green}GIT_DIR!${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear}):AFTER\\nGIT_DIR!" >expected &&
 	echo "dirty" >file &&
 	test_when_finished "git reset --hard" &&
 	(
@@ -547,13 +547,13 @@ test_expect_success 'prompt - bash color pc mode - inside .git directory' '
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		cd .git &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - stash status indicator' '
-	printf "BEFORE: (${c_green}master${c_clear} ${c_lblue}\$${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear} ${c_lblue}\$${c_clear}):AFTER\\nmaster" >expected &&
 	echo 2 >file &&
 	git stash &&
 	test_when_finished "git stash drop" &&
@@ -561,29 +561,29 @@ test_expect_success 'prompt - bash color pc mode - stash status indicator' '
 		GIT_PS1_SHOWSTASHSTATE=y &&
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - bash color pc mode - untracked files status indicator' '
-	printf "BEFORE: (${c_green}master${c_clear} ${c_red}%%${c_clear}):AFTER" >expected &&
+	printf "BEFORE: (${c_green}\${__git_ps1_branch_name}${c_clear} ${c_red}%%${c_clear}):AFTER\\nmaster" >expected &&
 	(
 		GIT_PS1_SHOWUNTRACKEDFILES=y &&
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		__git_ps1 "BEFORE:" ":AFTER" &&
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - zsh color pc mode' '
-	printf "BEFORE: (%%F{green}master%%f):AFTER" >expected &&
+	printf "BEFORE: (%%F{green}\${__git_ps1_branch_name}%%f):AFTER\\nmaster" >expected &&
 	(
 		ZSH_VERSION=5.0.0 &&
 		GIT_PS1_SHOWCOLORHINTS=y &&
 		__git_ps1 "BEFORE:" ":AFTER" >"$actual"
-		printf "%s" "$PS1" >"$actual"
+		printf "%s\\n%s" "$PS1" "${__git_ps1_branch_name}" >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '