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support for encrypted PEM keys #128

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support for encrypted PEM keys #128

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db281ae
pkey.toPEM: opts: rename const array
kunkku Sep 2, 2018
24ff6da
pkey.toPEM: accept table arguments
kunkku Sep 2, 2018
2f246cc
pkey.toPEM: private key encryption
kunkku Apr 30, 2018
312269d
pkey.new: type: rename variable
kunkku Sep 2, 2018
1d6f159
pkey.new: opt: rename variable
kunkku Sep 2, 2018
53fd95f
pkey.new: accept option table
kunkku Sep 2, 2018
89f26bb
pkey.new: decryption
kunkku Apr 30, 2018
4f41ae9
pkey.toPEM: use password callback
kunkku May 3, 2018
652de88
pkey: PEM password callback
kunkku May 3, 2018
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111 changes: 95 additions & 16 deletions src/openssl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@

#include <limits.h> /* INT_MAX INT_MIN LLONG_MAX LLONG_MIN UCHAR_MAX ULLONG_MAX */
#include <stdint.h> /* uintptr_t */
#include <string.h> /* memset(3) strerror_r(3) */
#include <string.h> /* memset(3) strerror_r(3) strlen(3) strncpy(3) */
#include <math.h> /* INFINITY fabs(3) floor(3) frexp(3) fmod(3) round(3) isfinite(3) */
#include <time.h> /* struct tm time_t strptime(3) time(2) */
#include <ctype.h> /* isdigit(3), isxdigit(3), tolower(3) */
Expand Down Expand Up @@ -4062,10 +4062,42 @@ static BIO *getbio(lua_State *L) {
} /* getbio() */


/*
* PEM password callback for openssl
*
* Expects nil, string, or function on top of the stack. Errors from the
* user-provided function are not reported. Leaves one item on the top of the
* stack: nil, the original string, or the return value.
*
* This callback may be called twice by pk_new when the PEM key is encrypted
* and its type is not specified. The user-provided function is called only
* once because it gets replaced on the stack by the return value. This
* callback may not be called at all if the supplied PEM key is not encrypted.
*/
static int pem_pw_cb(char *buf, int size, int rwflag, void *u) {
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Maybe worth adding a comment of "expects nil/function/string on top of the stack" and "leaves one item on the top of the stack".

"errors from the function are not reported"

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perhaps it should leave nothing on the stack?

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Requested comments added.

lua_State *L = (lua_State *) u;

if (lua_isfunction(L, -1) && lua_pcall(L, 0, 1, 0)) {
lua_pop(L, 1);
lua_pushnil(L);
}

if (lua_isnil(L, -1))
return 0;

const char *pass = lua_tostring(L, -1);
if (!pass)
return 0;

strncpy(buf, pass, size);
return MIN(strlen(pass), (unsigned int) size);
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} /* pem_pw_cb() */


static int pk_new(lua_State *L) {
EVP_PKEY **ud;

/* #1 table or key; if key, #2 format and #3 type */
/* #1 table or key; if key, #2 option table or format; if format, #3 type */
lua_settop(L, 3);

if (lua_istable(L, 1) || lua_isnil(L, 1)) {
Expand Down Expand Up @@ -4299,33 +4331,53 @@ static int pk_new(lua_State *L) {
#endif
} /* switch() */
} else if (lua_isstring(L, 1)) {
int type = optencoding(L, 2, "*", X509_ANY|X509_PEM|X509_DER);
int format;
int pubonly = 0, prvtonly = 0;
const char *opt, *data;
const char *type, *data;
size_t len;
BIO *bio;
EVP_PKEY *pub = NULL, *prvt = NULL;
int goterr = 0;

if (lua_istable(L, 2)) {
lua_pop(L, 1);
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this could be popping the table itself; or the 3rd argument.

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It is always the 3rd argument because stack size is set to 3 on line 4101. Of course, this can be changed to lua_remove if you prefer it that way.

lua_getfield(L, 2, "format");
lua_getfield(L, 2, "type");
lua_getfield(L, 2, "password");
lua_remove(L, 2);
} else
lua_pushnil(L);
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This branch only pushes one item vs the other branch's 3

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Now the net amount of pushed items is 1 in both branches.


/* #1 key, #2 format, #3 type, #4 password or callback */

data = luaL_checklstring(L, 1, &len);
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the error message for this will have the wrong index

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What should it be then? This was just moved from line 4321 to process the arguments in ascending order. The purpose was to improve readability.

format = optencoding(L, 2, "*", X509_ANY|X509_PEM|X509_DER);

/* check if specified publickey or privatekey */
if ((opt = luaL_optstring(L, 3, NULL))) {
if (xtolower(opt[0]) == 'p' && xtolower(opt[1]) == 'u') {
if ((type = luaL_optstring(L, 3, NULL))) {
if (xtolower(type[0]) == 'p' && xtolower(type[1]) == 'u') {
pubonly = 1;
} else if (xtolower(opt[0]) == 'p' && xtolower(opt[1]) == 'r') {
} else if (xtolower(type[0]) == 'p' && xtolower(type[1]) == 'r') {
prvtonly = 1;
} else {
return luaL_argerror(L, 3, lua_pushfstring(L, "invalid option %s", opt));
return luaL_error(L, "invalid key type: %s", type);
}
}

data = luaL_checklstring(L, 1, &len);
if (!lua_isnil(L, 4)) {
if (format == X509_DER)
return luaL_error(L, "decryption supported only for PEM keys");
else format = X509_PEM;
}

ud = prepsimple(L, PKEY_CLASS);

if (!(bio = BIO_new_mem_buf((void *)data, len)))
return auxL_error(L, auxL_EOPENSSL, "pkey.new");

if (type == X509_PEM || type == X509_ANY) {
if (format == X509_PEM || format == X509_ANY) {
lua_pushvalue(L, 4);

if (!prvtonly && !pub) {
/*
* BIO_reset is a rewind for read-only
Expand All @@ -4334,19 +4386,21 @@ static int pk_new(lua_State *L) {
*/
BIO_reset(bio);

if (!(pub = PEM_read_bio_PUBKEY(bio, NULL, 0, "")))
if (!(pub = PEM_read_bio_PUBKEY(bio, NULL, pem_pw_cb, L)))
goterr = 1;
}

if (!pubonly && !prvt) {
BIO_reset(bio);

if (!(prvt = PEM_read_bio_PrivateKey(bio, NULL, 0, "")))
if (!(prvt = PEM_read_bio_PrivateKey(bio, NULL, pem_pw_cb, L)))
goterr = 1;
}

lua_pop(L, 1);
}

if (type == X509_DER || type == X509_ANY) {
if (format == X509_DER || format == X509_ANY) {
if (!prvtonly && !pub) {
BIO_reset(bio);

Expand Down Expand Up @@ -4675,14 +4729,27 @@ static int pk_toPEM(lua_State *L) {
bio = getbio(L);

for (i = 2; i <= top; i++) {
static const char *const opts[] = {
static const char *const types[] = {
"public", "PublicKey",
"private", "PrivateKey",
// "params", "Parameters",
NULL,
};
int type;
const char *cname = NULL;
const EVP_CIPHER *cipher = NULL;

if (lua_istable(L, i)) {
loadfield(L, i, "cipher", LUA_TSTRING, &cname);
if (!getfield(L, i, "type"))
lua_pushstring(L, cname ? "private" : "public");
} else
lua_pushvalue(L, i);

type = auxL_checkoption(L, -1, NULL, types, 1);
lua_pop(L, 1);

switch (auxL_checkoption(L, i, NULL, opts, 1)) {
switch (type) {
case 0: case 1: /* public, PublicKey */
if (!PEM_write_bio_PUBKEY(bio, key))
return auxL_error(L, auxL_EOPENSSL, "pkey:__tostring");
Expand All @@ -4693,9 +4760,21 @@ static int pk_toPEM(lua_State *L) {

break;
case 2: case 3: /* private, PrivateKey */
if (!PEM_write_bio_PrivateKey(bio, key, 0, 0, 0, 0, 0))
if (cname) {
cipher = EVP_get_cipherbyname(cname);
if (!cipher)
return luaL_error(L, "pkey:toPEM: unknown cipher: %s", cname);
if (!getfield(L, i, "password"))
return luaL_error(L, "pkey:toPEM: password not defined");
}
else
lua_pushnil(L);

if (!PEM_write_bio_PrivateKey(bio, key, cipher, NULL, 0, pem_pw_cb, L))
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if there is no cname on the stack then what will be at top of stack?

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Added an else branch which pushes a nil value. The value will not be used because openssl will not invoke the callback when cipher equals NULL.

return auxL_error(L, auxL_EOPENSSL, "pkey:__tostring");

lua_pop(L, 1);

len = BIO_get_mem_data(bio, &pem);
lua_pushlstring(L, pem, len);
BIO_reset(bio);
Expand Down