From 404160a533ff8d2226dd3591a3584436aaf95f0b Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Mon, 8 Jan 2024 13:45:49 +0000 Subject: [PATCH 1/9] Move calculating RR into a separate function So far we needed it only locally here, but we will need calculating RR for safe unblinding in RSA as well. Signed-off-by: Janos Follath --- library/bignum.c | 18 +++++++++++++++--- library/bignum_internal.h | 31 +++++++++++++++++++++++++++++++ 2 files changed, 46 insertions(+), 3 deletions(-) create mode 100644 library/bignum_internal.h diff --git a/library/bignum.c b/library/bignum.c index 3e1c48c320..551fd81dd9 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -2039,6 +2039,20 @@ cleanup: return ret; } +int mbedtls_mpi_get_mont_r2_unsafe(mbedtls_mpi *X, + const mbedtls_mpi *N) +{ + int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; + + MBEDTLS_MPI_CHK(mbedtls_mpi_lset(X, 1)); + MBEDTLS_MPI_CHK(mbedtls_mpi_shift_l(X, N->n * 2 * biL)); + MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(X, X, N)); + MBEDTLS_MPI_CHK(mbedtls_mpi_shrink(X, N->n)); + +cleanup: + return ret; +} + /* * Sliding-window exponentiation: X = A^E mod N (HAC 14.85) */ @@ -2153,9 +2167,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, * If 1st call, pre-compute R^2 mod N */ if (prec_RR == NULL || prec_RR->p == NULL) { - MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&RR, 1)); - MBEDTLS_MPI_CHK(mbedtls_mpi_shift_l(&RR, N->n * 2 * biL)); - MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&RR, &RR, N)); + mbedtls_mpi_get_mont_r2_unsafe(&RR, N); if (prec_RR != NULL) { memcpy(prec_RR, &RR, sizeof(mbedtls_mpi)); diff --git a/library/bignum_internal.h b/library/bignum_internal.h new file mode 100644 index 0000000000..39909f3dd8 --- /dev/null +++ b/library/bignum_internal.h @@ -0,0 +1,31 @@ +/** + * Low level bignum functions + * + * Copyright The Mbed TLS Contributors + * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later + */ + +#ifndef MBEDTLS_BIGNUM_INTERNAL_H +#define MBEDTLS_BIGNUM_INTERNAL_H + +#include "mbedtls/bignum.h" + +/** + * \brief Calculate the square of the Montgomery constant. (Needed + * for conversion and operations in Montgomery form.) + * + * \param[out] X A pointer to the result of the calculation of + * the square of the Montgomery constant: + * 2^{2*n*biL} mod N. + * \param[in] N Little-endian presentation of the modulus, which must be odd. + * + * \return 0 if successful. + * \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if there is not enough space + * to store the value of Montgomery constant squared. + * \return #MBEDTLS_ERR_MPI_DIVISION_BY_ZERO if \p N modulus is zero. + * \return #MBEDTLS_ERR_MPI_NEGATIVE_VALUE if \p N modulus is negative. + */ +int mbedtls_mpi_get_mont_r2_unsafe(mbedtls_mpi *X, + const mbedtls_mpi *N); + +#endif /* MBEDTLS_BIGNUM_INTERNAL_H */ From f9cc4763f1b882aa2be0b59a9e8ab957d34644b7 Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Mon, 8 Jan 2024 14:08:17 +0000 Subject: [PATCH 2/9] Move some bignum functions to internal header We will need a couple of low level functions to implement safe unblinding in RSA. Signed-off-by: Janos Follath --- library/bignum.c | 67 ++++++++++++++------------------------- library/bignum_internal.h | 40 +++++++++++++++++++++++ 2 files changed, 63 insertions(+), 44 deletions(-) diff --git a/library/bignum.c b/library/bignum.c index 551fd81dd9..50da6b33b5 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -1907,7 +1907,7 @@ int mbedtls_mpi_mod_int(mbedtls_mpi_uint *r, const mbedtls_mpi *A, mbedtls_mpi_s /* * Fast Montgomery initialization (thanks to Tom St Denis) */ -static void mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N) +void mbedtls_mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N) { mbedtls_mpi_uint x, m0 = N->p[0]; unsigned int i; @@ -1922,33 +1922,11 @@ static void mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N) *mm = ~x + 1; } -/** Montgomery multiplication: A = A * B * R^-1 mod N (HAC 14.36) - * - * \param[in,out] A One of the numbers to multiply. - * It must have at least as many limbs as N - * (A->n >= N->n), and any limbs beyond n are ignored. - * On successful completion, A contains the result of - * the multiplication A * B * R^-1 mod N where - * R = (2^ciL)^n. - * \param[in] B One of the numbers to multiply. - * It must be nonzero and must not have more limbs than N - * (B->n <= N->n). - * \param[in] N The modulo. N must be odd. - * \param mm The value calculated by `mpi_montg_init(&mm, N)`. - * This is -N^-1 mod 2^ciL. - * \param[in,out] T A bignum for temporary storage. - * It must be at least twice the limb size of N plus 2 - * (T->n >= 2 * (N->n + 1)). - * Its initial content is unused and - * its final content is indeterminate. - * Note that unlike the usual convention in the library - * for `const mbedtls_mpi*`, the content of T can change. - */ -static void mpi_montmul(mbedtls_mpi *A, - const mbedtls_mpi *B, - const mbedtls_mpi *N, - mbedtls_mpi_uint mm, - const mbedtls_mpi *T) +void mbedtls_mpi_montmul(mbedtls_mpi *A, + const mbedtls_mpi *B, + const mbedtls_mpi *N, + mbedtls_mpi_uint mm, + const mbedtls_mpi *T) { size_t i, n, m; mbedtls_mpi_uint u0, u1, *d; @@ -1996,7 +1974,8 @@ static void mpi_montmul(mbedtls_mpi *A, /* * Montgomery reduction: A = A * R^-1 mod N * - * See mpi_montmul() regarding constraints and guarantees on the parameters. + * See mbedtls_mpi_montmul() regarding constraints and guarantees on the + * parameters. */ static void mpi_montred(mbedtls_mpi *A, const mbedtls_mpi *N, mbedtls_mpi_uint mm, const mbedtls_mpi *T) @@ -2007,7 +1986,7 @@ static void mpi_montred(mbedtls_mpi *A, const mbedtls_mpi *N, U.n = U.s = (int) z; U.p = &z; - mpi_montmul(A, &U, N, mm, T); + mbedtls_mpi_montmul(A, &U, N, mm, T); } /** @@ -2090,7 +2069,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, /* * Init temps and window size */ - mpi_montg_init(&mm, N); + mbedtls_mpi_montg_init(&mm, N); mbedtls_mpi_init(&RR); mbedtls_mpi_init(&T); mbedtls_mpi_init(&Apos); mbedtls_mpi_init(&WW); @@ -2144,10 +2123,10 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, j = N->n + 1; /* All W[i] including the accumulator must have at least N->n limbs for - * the mpi_montmul() and mpi_montred() calls later. Here we ensure that - * W[1] and the accumulator W[x_index] are large enough. later we'll grow - * other W[i] to the same length. They must not be shrunk midway through - * this function! + * the mbedtls_mpi_montmul() and mpi_montred() calls later. Here we ensure + * that W[1] and the accumulator W[x_index] are large enough. later we'll + * grow other W[i] to the same length. They must not be shrunk midway + * through this function! */ MBEDTLS_MPI_CHK(mbedtls_mpi_grow(&W[x_index], j)); MBEDTLS_MPI_CHK(mbedtls_mpi_grow(&W[1], j)); @@ -2183,7 +2162,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&W[1], A, N)); /* This should be a no-op because W[1] is already that large before * mbedtls_mpi_mod_mpi(), but it's necessary to avoid an overflow - * in mpi_montmul() below, so let's make sure. */ + * in mbedtls_mpi_montmul() below, so let's make sure. */ MBEDTLS_MPI_CHK(mbedtls_mpi_grow(&W[1], N->n + 1)); } else { MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&W[1], A)); @@ -2191,7 +2170,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, /* Note that this is safe because W[1] always has at least N->n limbs * (it grew above and was preserved by mbedtls_mpi_copy()). */ - mpi_montmul(&W[1], &RR, N, mm, &T); + mbedtls_mpi_montmul(&W[1], &RR, N, mm, &T); /* * W[x_index] = R^2 * R^-1 mod N = R mod N @@ -2217,7 +2196,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&W[j], &W[1])); for (i = 0; i < window_bitsize - 1; i++) { - mpi_montmul(&W[j], &W[j], N, mm, &T); + mbedtls_mpi_montmul(&W[j], &W[j], N, mm, &T); } /* @@ -2227,7 +2206,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, MBEDTLS_MPI_CHK(mbedtls_mpi_grow(&W[i], N->n + 1)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&W[i], &W[i - 1])); - mpi_montmul(&W[i], &W[1], N, mm, &T); + mbedtls_mpi_montmul(&W[i], &W[1], N, mm, &T); } } @@ -2263,7 +2242,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, * out of window, square W[x_index] */ MBEDTLS_MPI_CHK(mpi_select(&WW, W, w_table_used_size, x_index)); - mpi_montmul(&W[x_index], &WW, N, mm, &T); + mbedtls_mpi_montmul(&W[x_index], &WW, N, mm, &T); continue; } @@ -2282,7 +2261,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, for (i = 0; i < window_bitsize; i++) { MBEDTLS_MPI_CHK(mpi_select(&WW, W, w_table_used_size, x_index)); - mpi_montmul(&W[x_index], &WW, N, mm, &T); + mbedtls_mpi_montmul(&W[x_index], &WW, N, mm, &T); } /* @@ -2290,7 +2269,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, */ MBEDTLS_MPI_CHK(mpi_select(&WW, W, w_table_used_size, exponent_bits_in_window)); - mpi_montmul(&W[x_index], &WW, N, mm, &T); + mbedtls_mpi_montmul(&W[x_index], &WW, N, mm, &T); state--; nbits = 0; @@ -2303,13 +2282,13 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, */ for (i = 0; i < nbits; i++) { MBEDTLS_MPI_CHK(mpi_select(&WW, W, w_table_used_size, x_index)); - mpi_montmul(&W[x_index], &WW, N, mm, &T); + mbedtls_mpi_montmul(&W[x_index], &WW, N, mm, &T); exponent_bits_in_window <<= 1; if ((exponent_bits_in_window & ((size_t) 1 << window_bitsize)) != 0) { MBEDTLS_MPI_CHK(mpi_select(&WW, W, w_table_used_size, 1)); - mpi_montmul(&W[x_index], &WW, N, mm, &T); + mbedtls_mpi_montmul(&W[x_index], &WW, N, mm, &T); } } diff --git a/library/bignum_internal.h b/library/bignum_internal.h index 39909f3dd8..f14c294a5a 100644 --- a/library/bignum_internal.h +++ b/library/bignum_internal.h @@ -28,4 +28,44 @@ int mbedtls_mpi_get_mont_r2_unsafe(mbedtls_mpi *X, const mbedtls_mpi *N); +/** + * \brief Calculate initialisation value for fast Montgomery modular + * multiplication. + * + * \param[out] mm The initialisation value for fast Montgomery modular + * multiplication. + * \param[in] N Little-endian presentation of the modulus. This must have + * at least one limb. + */ +void mbedtls_mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N); + +/** Montgomery multiplication: A = A * B * R^-1 mod N (HAC 14.36) + * + * \param[in,out] A One of the numbers to multiply. + * It must have at least as many limbs as N + * (A->n >= N->n), and any limbs beyond n are ignored. + * On successful completion, A contains the result of + * the multiplication A * B * R^-1 mod N where + * R = (2^ciL)^n. + * \param[in] B One of the numbers to multiply. + * It must be nonzero and must not have more limbs than N + * (B->n <= N->n). + * \param[in] N The modulo. N must be odd. + * \param mm The value calculated by + * `mbedtls_mpi_montg_init(&mm, N)`. + * This is -N^-1 mod 2^ciL. + * \param[in,out] T A bignum for temporary storage. + * It must be at least twice the limb size of N plus 2 + * (T->n >= 2 * (N->n + 1)). + * Its initial content is unused and + * its final content is indeterminate. + * Note that unlike the usual convention in the library + * for `const mbedtls_mpi*`, the content of T can change. + */ +void mbedtls_mpi_montmul(mbedtls_mpi *A, + const mbedtls_mpi *B, + const mbedtls_mpi *N, + mbedtls_mpi_uint mm, + const mbedtls_mpi *T); + #endif /* MBEDTLS_BIGNUM_INTERNAL_H */ From 8b246b3d16407bf2ee1cd33122538290157cb8f0 Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Mon, 8 Jan 2024 15:09:34 +0000 Subject: [PATCH 3/9] Make RSA unblinding constant flow Signed-off-by: Janos Follath --- library/rsa.c | 45 +++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 43 insertions(+), 2 deletions(-) diff --git a/library/rsa.c b/library/rsa.c index 84403c4579..937d4aacdb 100644 --- a/library/rsa.c +++ b/library/rsa.c @@ -34,6 +34,7 @@ #include "mbedtls/error.h" #include "constant_time_internal.h" #include "mbedtls/constant_time.h" +#include "bignum_internal.h" #include @@ -804,6 +805,47 @@ cleanup: return ret; } +/* + * Unblind + * T = T * Vf mod N + */ +static int rsa_unblind(mbedtls_mpi *T, mbedtls_mpi *Vf, const mbedtls_mpi *N) +{ + int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; + const size_t nlimbs = N->n; + const size_t tlimbs = 2 * (nlimbs + 1); + + mbedtls_mpi_uint mm; + mbedtls_mpi_montg_init(&mm, N); + + mbedtls_mpi RR, M_T; + + mbedtls_mpi_init(&RR); + mbedtls_mpi_init(&M_T); + + MBEDTLS_MPI_CHK(mbedtls_mpi_get_mont_r2_unsafe(&RR, N)); + MBEDTLS_MPI_CHK(mbedtls_mpi_grow(&M_T, tlimbs)); + + MBEDTLS_MPI_CHK(mbedtls_mpi_grow(T, nlimbs)); + MBEDTLS_MPI_CHK(mbedtls_mpi_grow(Vf, nlimbs)); + + /* T = T * Vf mod N + * Reminder: montmul(A, B, N) = A * B * R^-1 mod N + * Usually both operands are multiplied by R mod N beforehand, yielding a + * result that's also * R mod N (aka "in the Montgomery domain"). Here we + * only multiply one operand by R mod N, so the result is directly what we + * want - no need to call `mpi_montred()` on it. */ + mbedtls_mpi_montmul(T, &RR, N, mm, &M_T); + mbedtls_mpi_montmul(T, Vf, N, mm, &M_T); + +cleanup: + + mbedtls_mpi_free(&RR); + mbedtls_mpi_free(&M_T); + + return ret; +} + /* * Exponent blinding supposed to prevent side-channel attacks using multiple * traces of measurements to recover the RSA key. The more collisions are there, @@ -1000,8 +1042,7 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, * Unblind * T = T * Vf mod N */ - MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&T, &T, &ctx->Vf)); - MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&T, &T, &ctx->N)); + MBEDTLS_MPI_CHK(rsa_unblind(&T, &ctx->Vf, &ctx->N)); } /* Verify the result to prevent glitching attacks. */ From 24bb226232edfd0c31e54ad0ae36654428097230 Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Mon, 8 Jan 2024 15:19:11 +0000 Subject: [PATCH 4/9] Extend blinding to RSA result check Signed-off-by: Janos Follath --- library/rsa.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/library/rsa.c b/library/rsa.c index 937d4aacdb..23fe84310b 100644 --- a/library/rsa.c +++ b/library/rsa.c @@ -909,7 +909,7 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, /* Temporaries holding the initial input and the double * checked result; should be the same in the end. */ - mbedtls_mpi I, C; + mbedtls_mpi input_blinded, check_result_blinded; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(input != NULL); @@ -946,8 +946,8 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, mbedtls_mpi_init(&TP); mbedtls_mpi_init(&TQ); #endif - mbedtls_mpi_init(&I); - mbedtls_mpi_init(&C); + mbedtls_mpi_init(&input_blinded); + mbedtls_mpi_init(&check_result_blinded); /* End of MPI initialization */ @@ -957,8 +957,6 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, goto cleanup; } - MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&I, &T)); - if (f_rng != NULL) { /* * Blinding @@ -1010,6 +1008,9 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, #endif /* MBEDTLS_RSA_NO_CRT */ } + /* Make a copy of the input (after blinding if there was any) */ + MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&input_blinded, &T)); + #if defined(MBEDTLS_RSA_NO_CRT) MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&T, &T, D, &ctx->N, &ctx->RN)); #else @@ -1037,6 +1038,14 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&T, &TQ, &TP)); #endif /* MBEDTLS_RSA_NO_CRT */ + /* Verify the result to prevent glitching attacks. */ + MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&check_result_blinded, &T, &ctx->E, + &ctx->N, &ctx->RN)); + if (mbedtls_mpi_cmp_mpi(&check_result_blinded, &input_blinded) != 0) { + ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; + goto cleanup; + } + if (f_rng != NULL) { /* * Unblind @@ -1045,14 +1054,6 @@ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, MBEDTLS_MPI_CHK(rsa_unblind(&T, &ctx->Vf, &ctx->N)); } - /* Verify the result to prevent glitching attacks. */ - MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&C, &T, &ctx->E, - &ctx->N, &ctx->RN)); - if (mbedtls_mpi_cmp_mpi(&C, &I) != 0) { - ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; - goto cleanup; - } - olen = ctx->len; MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&T, output, olen)); @@ -1082,8 +1083,8 @@ cleanup: mbedtls_mpi_free(&TP); mbedtls_mpi_free(&TQ); #endif - mbedtls_mpi_free(&C); - mbedtls_mpi_free(&I); + mbedtls_mpi_free(&check_result_blinded); + mbedtls_mpi_free(&input_blinded); if (ret != 0 && ret >= -0x007f) { return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_RSA_PRIVATE_FAILED, ret); From 54b2edaa8b336da76a4439e7e93f310d18c87714 Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Fri, 29 Dec 2023 11:14:58 +0000 Subject: [PATCH 5/9] Add warning for PKCS 1.5 decryption Any timing variance dependant on the output of this function enables a Bleichenbacher attack. It is extremely difficult to use safely. In the Marvin attack paper (https://people.redhat.com/~hkario/marvin/marvin-attack-paper.pdf) the author suggests that implementations of PKCS 1.5 decryption that don't include a countermeasure should be considered inherently dangerous. They suggest that all libraries implement the same countermeasure, as implementing different countermeasures across libraries enables the Bleichenbacher attack as well. This is extremely fragile and therefore we don't implement it. The use of PKCS 1.5 in Mbed TLS implements the countermeasures recommended in the TLS standard (7.4.7.1 of RFC 5246) and is not vulnerable. Add a warning to PKCS 1.5 decryption to warn users about this. Signed-off-by: Janos Follath --- include/mbedtls/rsa.h | 9 +++++++++ include/psa/crypto_values.h | 7 +++++++ 2 files changed, 16 insertions(+) diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h index 667e6257e6..1779775155 100644 --- a/include/mbedtls/rsa.h +++ b/include/mbedtls/rsa.h @@ -712,6 +712,10 @@ int mbedtls_rsa_rsaes_oaep_encrypt(mbedtls_rsa_context *ctx, * It is the generic wrapper for performing a PKCS#1 decryption * operation using the \p mode from the context. * + * \warning When \p ctx->padding is set to #MBEDTLS_RSA_PKCS_V15, + * mbedtls_rsa_rsaes_pkcs1_v15_decrypt() is called, which is an + * inherently dangerous function (CWE-242). + * * \note The output buffer length \c output_max_len should be * as large as the size \p ctx->len of \p ctx->N (for example, * 128 Bytes if RSA-1024 is used) to be able to hold an @@ -761,6 +765,11 @@ int mbedtls_rsa_pkcs1_decrypt(mbedtls_rsa_context *ctx, * \brief This function performs a PKCS#1 v1.5 decryption * operation (RSAES-PKCS1-v1_5-DECRYPT). * + * \warning This is an inherently dangerous function (CWE-242). Unless + * it is used in a side channel free and safe way (eg. + * implementing the TLS protocol as per 7.4.7.1 of RFC 5246), + * the calling code is vulnerable. + * * \note The output buffer length \c output_max_len should be * as large as the size \p ctx->len of \p ctx->N, for example, * 128 Bytes if RSA-1024 is used, to be able to hold an diff --git a/include/psa/crypto_values.h b/include/psa/crypto_values.h index a398249904..c25fda63ec 100644 --- a/include/psa/crypto_values.h +++ b/include/psa/crypto_values.h @@ -1659,6 +1659,13 @@ 0) /** RSA PKCS#1 v1.5 encryption. + * + * \warning Calling psa_asymmetric_decrypt() with this algorithm as a + * parameter is considered an inherently dangerous function + * (CWE-242). Unless it is used in a side channel free and safe + * way (eg. implementing the TLS protocol as per 7.4.7.1 of + * RFC 5246), the calling code is vulnerable. + * */ #define PSA_ALG_RSA_PKCS1V15_CRYPT ((psa_algorithm_t) 0x07000200) From d50f7a7a17bc7b64d16470d30656e0859121cfd0 Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Tue, 21 Nov 2023 09:57:27 +0000 Subject: [PATCH 6/9] Add Changelog for the Marvin attack fix Signed-off-by: Janos Follath --- ChangeLog.d/fix-Marvin-attack.txt | 6 ++++++ 1 file changed, 6 insertions(+) create mode 100644 ChangeLog.d/fix-Marvin-attack.txt diff --git a/ChangeLog.d/fix-Marvin-attack.txt b/ChangeLog.d/fix-Marvin-attack.txt new file mode 100644 index 0000000000..017f7b1f80 --- /dev/null +++ b/ChangeLog.d/fix-Marvin-attack.txt @@ -0,0 +1,6 @@ +Security + * Fix a timing side channel in RSA private operations. This side channel + could be sufficient for a local attacker to recover the plaintext. It + requires the attacker to send a large number of messages for decryption. + For details, see "Everlasting ROBOT: the Marvin Attack", Hubert Kario. + Reported by Hubert Kario, Red Hat. From 6f499b7ed4206b47259c9b413ae17082478c3dad Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Tue, 9 Jan 2024 09:28:48 +0000 Subject: [PATCH 7/9] Align Montgomery init with development The signature and naming of the Montgomrey initialisation function in development and in the LTS was different. Align them for easier readability and maintenance. Signed-off-by: Janos Follath --- library/bignum.c | 16 +++++++--------- library/bignum_internal.h | 12 ++++++------ library/rsa.c | 3 +-- 3 files changed, 14 insertions(+), 17 deletions(-) diff --git a/library/bignum.c b/library/bignum.c index 50da6b33b5..74f10af8d5 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -1907,19 +1907,17 @@ int mbedtls_mpi_mod_int(mbedtls_mpi_uint *r, const mbedtls_mpi *A, mbedtls_mpi_s /* * Fast Montgomery initialization (thanks to Tom St Denis) */ -void mbedtls_mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N) +mbedtls_mpi_uint mbedtls_mpi_montmul_init(const mbedtls_mpi_uint *N) { - mbedtls_mpi_uint x, m0 = N->p[0]; - unsigned int i; + mbedtls_mpi_uint x = N[0]; - x = m0; - x += ((m0 + 2) & 4) << 1; + x += ((N[0] + 2) & 4) << 1; - for (i = biL; i >= 8; i /= 2) { - x *= (2 - (m0 * x)); + for (unsigned int i = biL; i >= 8; i /= 2) { + x *= (2 - (N[0] * x)); } - *mm = ~x + 1; + return ~x + 1; } void mbedtls_mpi_montmul(mbedtls_mpi *A, @@ -2069,7 +2067,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A, /* * Init temps and window size */ - mbedtls_mpi_montg_init(&mm, N); + mm = mbedtls_mpi_montmul_init(N->p); mbedtls_mpi_init(&RR); mbedtls_mpi_init(&T); mbedtls_mpi_init(&Apos); mbedtls_mpi_init(&WW); diff --git a/library/bignum_internal.h b/library/bignum_internal.h index f14c294a5a..5435ebb464 100644 --- a/library/bignum_internal.h +++ b/library/bignum_internal.h @@ -30,14 +30,14 @@ int mbedtls_mpi_get_mont_r2_unsafe(mbedtls_mpi *X, /** * \brief Calculate initialisation value for fast Montgomery modular - * multiplication. + * multiplication * - * \param[out] mm The initialisation value for fast Montgomery modular - * multiplication. - * \param[in] N Little-endian presentation of the modulus. This must have - * at least one limb. + * \param[in] N Little-endian presentation of the modulus. This must have + * at least one limb. + * + * \return The initialisation value for fast Montgomery modular multiplication */ -void mbedtls_mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N); +mbedtls_mpi_uint mbedtls_mpi_montmul_init(const mbedtls_mpi_uint *N); /** Montgomery multiplication: A = A * B * R^-1 mod N (HAC 14.36) * diff --git a/library/rsa.c b/library/rsa.c index 23fe84310b..0a0c2e3880 100644 --- a/library/rsa.c +++ b/library/rsa.c @@ -815,8 +815,7 @@ static int rsa_unblind(mbedtls_mpi *T, mbedtls_mpi *Vf, const mbedtls_mpi *N) const size_t nlimbs = N->n; const size_t tlimbs = 2 * (nlimbs + 1); - mbedtls_mpi_uint mm; - mbedtls_mpi_montg_init(&mm, N); + mbedtls_mpi_uint mm = mbedtls_mpi_montmul_init(N->p); mbedtls_mpi RR, M_T; From 8b736290adef79089084a8f3b8ba15c086805922 Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Tue, 9 Jan 2024 09:37:06 +0000 Subject: [PATCH 8/9] Fix 'missing prototype' warnings Signed-off-by: Janos Follath --- library/bignum.c | 1 + 1 file changed, 1 insertion(+) diff --git a/library/bignum.c b/library/bignum.c index 74f10af8d5..fadd9e9cc2 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -30,6 +30,7 @@ #include "mbedtls/platform_util.h" #include "mbedtls/error.h" #include "constant_time_internal.h" +#include "bignum_internal.h" #include #include From ce4a3c25fe36003c76b4c05ae1fa5286b91b4178 Mon Sep 17 00:00:00 2001 From: Janos Follath Date: Wed, 10 Jan 2024 08:54:17 +0000 Subject: [PATCH 9/9] Add new internal header to visualc project Signed-off-by: Janos Follath --- visualc/VS2010/mbedTLS.vcxproj | 1 + 1 file changed, 1 insertion(+) diff --git a/visualc/VS2010/mbedTLS.vcxproj b/visualc/VS2010/mbedTLS.vcxproj index 1ffc1f6e05..18b613ee02 100644 --- a/visualc/VS2010/mbedTLS.vcxproj +++ b/visualc/VS2010/mbedTLS.vcxproj @@ -260,6 +260,7 @@ +