From 0f8dd1faea639ec12b36a8af91e21aa44b87bf5c Mon Sep 17 00:00:00 2001
From: Jaime Alfaro Salazar <62313620+jialfaro@users.noreply.github.com>
Date: Sun, 6 Sep 2026 11:58:01 -0500
Subject: [PATCH] Fix #431: [bug bounty] readpass_file() silently truncates the
 passphrase at a carriage return

---
 libcperciva/util/readpass_file.c | 25 +++++++++++++++++++++++--
 tests/08-passphrase-file.sh      | 22 +++++++++++-----------
 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/libcperciva/util/readpass_file.c b/libcperciva/util/readpass_file.c
index 4379a61d..fa9f193c 100644
--- a/libcperciva/util/readpass_file.c
+++ b/libcperciva/util/readpass_file.c
@@ -52,8 +52,29 @@ readpass_file(char ** passwd, const char * filename)
 		goto err1;
 	}
 
-	/* Truncate at any newline character. */
-	passbuf[strcspn(passbuf, "\r\n")] = '\0';
+	/*
+	 * Strip a trailing "\n" or a trailing "\r\n" explicitly, then reject the
+	 * file if any "\r" or "\n" remains.  This matches the contract in
+	 * readpass.h: only a single trailing newline ("\n") or CRLF ("\r\n") is
+	 * permitted at the end of the file; any other occurrences of CR or LF are
+	 * an error.
+	 */
+	{
+		size_t len = strlen(passbuf);
+
+		/* Strip trailing '\n', and an optional preceding '\r'. */
+		if (len > 0 && passbuf[len - 1] == '\n') {
+			passbuf[--len] = '\0';
+			if (len > 0 && passbuf[len - 1] == '\r')
+				passbuf[--len] = '\0';
+		}
+
+		/* If any CR or LF remains, the file contains embedded newlines. */
+		if (strchr(passbuf, '\r') != NULL || strchr(passbuf, '\n') != NULL) {
+			warn0("Invalid passphrase file: %s", filename);
+			goto err1;
+		}
+	}
 
 	/* Copy the password out. */
 	if ((*passwd = strdup(passbuf)) == NULL) {
diff --git a/tests/08-passphrase-file.sh b/tests/08-passphrase-file.sh
index 1d1de088..ea743cfe 100644
--- a/tests/08-passphrase-file.sh
+++ b/tests/08-passphrase-file.sh
@@ -13,12 +13,12 @@ decrypted_no_file_log="${s_basename}-decrypt-no-file.log"
 
 scenario_cmd() {
 	# Create the passphrase file.
-	echo "${password}" > "${passphrase_file}"
+	printf "%s\n" "${password}" > "${passphrase_file}"
 
 	# Decrypt a reference file using --passphrase file:FILENAME.
 	setup_check "scrypt dec file"
-	${c_valgrind_cmd} "${bindir}/scrypt"				\
-	    dec --passphrase file:"${passphrase_file}"			\
+	${c_valgrind_cmd} "${bindir}/scrypt" 					\
+	    dec --passphrase file:"${passphrase_file}" 			\
 	    "${encrypted_reference_file}" "${decrypted_reference_file}"
 	echo $? > "${c_exitfile}"
 
@@ -30,15 +30,15 @@ scenario_cmd() {
 	# Attempt to decrypt the reference file with a non-existent file.
 	# We want this command to fail with 1.
 	setup_check "scrypt dec file none"
-	${c_valgrind_cmd} "${bindir}/scrypt"				\
-	    dec --passphrase file:THIS_FILE_DOES_NOT_EXIST		\
-	    "${encrypted_reference_file}" "${decrypted_reference_file}"	\
+	${c_valgrind_cmd} "${bindir}/scrypt" 					\
+	    dec --passphrase file:THIS_FILE_DOES_NOT_EXIST 		\
+	    "${encrypted_reference_file}" "${decrypted_reference_file}" 	\
 	    2> "${decrypted_no_file_log}"
 	expected_exitcode 1 $? > "${c_exitfile}"
 
 	# We should have received an error message.
 	setup_check "scrypt dec file none error"
-	grep -q	"scrypt: fopen(THIS_FILE_DOES_NOT_EXIST)"		\
+	grep -q	"scrypt: fopen(THIS_FILE_DOES_NOT_EXIST)" 		\
 	    "${decrypted_no_file_log}"
 	echo "$?" > "${c_exitfile}"
 
@@ -50,10 +50,10 @@ scenario_cmd() {
 	# Attempt to decrypt the reference file with an incorrect passphrase.
 	# We want this command to fail with 1.
 	setup_check "scrypt dec file bad"
-	echo "bad-pass" > "${bad_passphrase_file}"
-	${c_valgrind_cmd} "${bindir}/scrypt"				\
-	    dec --passphrase file:"${bad_passphrase_file}"		\
-	    "${encrypted_reference_file}" "${decrypted_reference_file}"	\
+	printf "bad-pass\n" > "${bad_passphrase_file}"
+	${c_valgrind_cmd} "${bindir}/scrypt" 					\
+	    dec --passphrase file:"${bad_passphrase_file}" 		\
+	    "${encrypted_reference_file}" "${decrypted_reference_file}" 	\
 	    2> "${decrypted_badpass_log}"
 	expected_exitcode 1 $? > "${c_exitfile}"