Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Set correct output length in PKCS#1 v1.5 depadding #3077

Merged
merged 4 commits into from
Apr 4, 2024
Merged

Set correct output length in PKCS#1 v1.5 depadding #3077

Changes from 1 commit
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
26bea00
padding: Set correct output length in PKCS#1 v1.5 depadding
xhanulik Mar 19, 2024
cc9e84d
minidriver: Remove logging to prevent Marvin attack
xhanulik Mar 20, 2024
5a7bffc
unittests: Test correct output length for PKCS#1 v1.5 depadding
xhanulik Mar 20, 2024
780e08b
minidriver: Refactor inversion of decrypted buffer
xhanulik Mar 21, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
Next Next commit
padding: Set correct output length in PKCS#1 v1.5 depadding
  • Loading branch information
@xhanulik
xhanulik committed Mar 27, 2024
commit 26bea0033edecf0f67dd195cc89780a734990709
15 changes: 9 additions & 6 deletions src/libopensc/padding.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -154,13 +154,15 @@ sc_pkcs1_strip_02_padding_constant_time(sc_context_t *ctx, unsigned int n, const
{
unsigned int i = 0;
u8 *msg, *msg_orig = NULL;
unsigned int good, found_zero_byte, mask;
unsigned int good, found_zero_byte, mask, tmp_outlen;
unsigned int zero_index = 0, msg_index, mlen = -1, len = 0;
LOG_FUNC_CALLED(ctx);

if (data == NULL || data_len <= 0 || data_len > n || n < SC_PKCS1_PADDING_MIN_SIZE)
if (data == NULL || data_len <= 0 || data_len > n ||
n < SC_PKCS1_PADDING_MIN_SIZE || out_len == NULL)
LOG_FUNC_RETURN(ctx, SC_ERROR_INTERNAL);

tmp_outlen = *out_len;
msg = msg_orig = calloc(n, sizeof(u8));
if (msg == NULL)
LOG_FUNC_RETURN(ctx, SC_ERROR_INTERNAL);
Expand Down Expand Up @@ -201,25 +203,26 @@ sc_pkcs1_strip_02_padding_constant_time(sc_context_t *ctx, unsigned int n, const
mlen = data_len - msg_index;

// check that message fits into out buffer
good &= constant_time_ge(*out_len, mlen);
good &= constant_time_ge(tmp_outlen, mlen);

// move the result in-place by |num|-SC_PKCS1_PADDING_MIN_SIZE-|mlen| bytes to the left.
*out_len = constant_time_select(constant_time_lt(n - SC_PKCS1_PADDING_MIN_SIZE, *out_len),
n - SC_PKCS1_PADDING_MIN_SIZE, *out_len);
tmp_outlen = constant_time_select(constant_time_lt(n - SC_PKCS1_PADDING_MIN_SIZE, tmp_outlen),
n - SC_PKCS1_PADDING_MIN_SIZE, tmp_outlen);
for (msg_index = 1; msg_index < n - SC_PKCS1_PADDING_MIN_SIZE; msg_index <<= 1) {
mask = ~constant_time_eq(msg_index & (n - SC_PKCS1_PADDING_MIN_SIZE - mlen), 0);
for (i = SC_PKCS1_PADDING_MIN_SIZE; i < n - msg_index; i++)
msg[i] = constant_time_select_8(mask, msg[i + msg_index], msg[i]);
}
// move message into out buffer, if good
for (i = 0; i < *out_len; i++) {
for (i = 0; i < tmp_outlen; i++) {
unsigned int msg_index;
// when out is longer than message in data, use some bogus index in msg
mask = good & constant_time_lt(i, mlen);
msg_index = constant_time_select(mask, i + SC_PKCS1_PADDING_MIN_SIZE, 0); // to now overflow msg buffer
out[i] = constant_time_select_8(mask, msg[msg_index], out[i]);
}

*out_len = constant_time_select(good, mlen, *out_len);
free(msg_orig);
return constant_time_select(good, mlen, SC_ERROR_WRONG_PADDING);
}
Expand Down