From 4e11e0a485dcc43cd30f7ea305ebc9718f5ec7f7 Mon Sep 17 00:00:00 2001 From: Timo Sirainen Date: Sun, 9 Apr 2017 00:50:15 +0300 Subject: [PATCH] auth: Make plaintext password comparisons safe against timing attacks --- src/auth/password-scheme.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/src/auth/password-scheme.c b/src/auth/password-scheme.c index aef63e2b8b..bacedb951d 100644 --- a/src/auth/password-scheme.c +++ b/src/auth/password-scheme.c @@ -609,6 +609,18 @@ plain_generate(const char *plaintext, const char *user ATTR_UNUSED, *size_r = strlen(plaintext); } +static int +plain_verify(const char *plaintext, const char *user ATTR_UNUSED, + const unsigned char *raw_password, size_t size, + const char **error_r ATTR_UNUSED) +{ + size_t plaintext_len = strlen(plaintext); + + if (plaintext_len != size) + return 0; + return mem_equals_timing_safe(plaintext, raw_password, size) ? 1 : 0; +} + static int plain_trunc_verify(const char *plaintext, const char *user ATTR_UNUSED, const unsigned char *raw_password, size_t size, @@ -633,10 +645,10 @@ plain_trunc_verify(const char *plaintext, const char *user ATTR_UNUSED, if (size-i == trunc_len && plaintext_len >= trunc_len) { /* possibly truncated password. allow the given password as long as the prefix matches. */ - return memcmp(raw_password+i, plaintext, trunc_len) == 0 ? 1 : 0; + return mem_equals_timing_safe(raw_password+i, plaintext, trunc_len) ? 1 : 0; } return plaintext_len == size-i && - memcmp(raw_password+i, plaintext, plaintext_len) == 0 ? 1 : 0; + mem_equals_timing_safe(raw_password+i, plaintext, plaintext_len) ? 1 : 0; } static void @@ -803,9 +815,9 @@ static const struct password_scheme builtin_schemes[] = { { "SSHA", PW_ENCODING_BASE64, 0, ssha_verify, ssha_generate }, { "SSHA256", PW_ENCODING_BASE64, 0, ssha256_verify, ssha256_generate }, { "SSHA512", PW_ENCODING_BASE64, 0, ssha512_verify, ssha512_generate }, - { "PLAIN", PW_ENCODING_NONE, 0, NULL, plain_generate }, - { "CLEAR", PW_ENCODING_NONE, 0, NULL, plain_generate }, - { "CLEARTEXT", PW_ENCODING_NONE, 0, NULL, plain_generate }, + { "PLAIN", PW_ENCODING_NONE, 0, plain_verify, plain_generate }, + { "CLEAR", PW_ENCODING_NONE, 0, plain_verify, plain_generate }, + { "CLEARTEXT", PW_ENCODING_NONE, 0, plain_verify, plain_generate }, { "PLAIN-TRUNC", PW_ENCODING_NONE, 0, plain_trunc_verify, plain_generate }, { "CRAM-MD5", PW_ENCODING_HEX, CRAM_MD5_CONTEXTLEN, NULL, cram_md5_generate }, -- 2.47.3