CVE-2019-12904 (C, published 2019-06-20T00:15Z)
Description: value: In Libgcrypt 1.8.4, the C implementation of AES is vulnerable to a flush-and-reload side-channel attack because physical addresses are available to other processes. (The C implementation is used on platforms where an assembly-language implementation is unavailable.) NOTE: the vendor's position is that the issue report cannot be validated because there is no description of an attack
Severity: MEDIUM (CVSS v3 base score: 5.9)
Weakness: CWE-668 \u2014 Exposure of Resource to Wrong Sphere
The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.
Repository: https://github.com/gpg/libgcrypt
Files changed:
cipher/rijndael-internal.h
cipher/rijndael-tables.h
cipher/rijndael.c
Commit message: AES: move look-up tables to .data section and unshare between processes

* cipher/rijndael-internal.h (ATTR_ALIGNED_64): New.
* cipher/rijndael-tables.h (encT): Move to 'enc_tables' structure.
(enc_tables): New structure for encryption table with counters before
and after.
(encT): New macro.
(dec_tables): Add counters before and after encryption table; Move
from .rodata to .data section.
(do_encrypt): Change 'encT' to 'enc_tables.T'.
(do_decrypt): Change '&dec_tables' to 'dec_tables.T'.
* cipher/cipher-gcm.c (prefetch_table): Make inline; Handle input
with length not multiple of 256.
(prefetch_enc, prefetch_dec): Modify pre- and post-table counters
to unshare look-up table pages between processes.
--

GnuPG-bug-id: 4541
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>


Vulnerable code:
/* Helper macro to force alignment to 16 bytes.  */
static const u32 encT[256] =
    0xa56363c6, 0x847c7cf8, 0x997777ee, 0x8d7b7bf6,
    0x0df2f2ff, 0xbd6b6bd6, 0xb16f6fde, 0x54c5c591,
    0x50303060, 0x03010102, 0xa96767ce, 0x7d2b2b56,
    0x19fefee7, 0x62d7d7b5, 0xe6abab4d, 0x9a7676ec,
    0x45caca8f, 0x9d82821f, 0x40c9c989, 0x877d7dfa,
    0x15fafaef, 0xeb5959b2, 0xc947478e, 0x0bf0f0fb,
    0xecadad41, 0x67d4d4b3, 0xfda2a25f, 0xeaafaf45,
    0xbf9c9c23, 0xf7a4a453, 0x967272e4, 0x5bc0c09b,
    0xc2b7b775, 0x1cfdfde1, 0xae93933d, 0x6a26264c,
    0x5a36366c, 0x413f3f7e, 0x02f7f7f5, 0x4fcccc83,
    0x5c343468, 0xf4a5a551, 0x34e5e5d1, 0x08f1f1f9,
    0x937171e2, 0x73d8d8ab, 0x53313162, 0x3f15152a,
    0x0c040408, 0x52c7c795, 0x65232346, 0x5ec3c39d,
    0x28181830, 0xa1969637, 0x0f05050a, 0xb59a9a2f,
    0x0907070e, 0x36121224, 0x9b80801b, 0x3de2e2df,
    0x26ebebcd, 0x6927274e, 0xcdb2b27f, 0x9f7575ea,
    0x1b090912, 0x9e83831d, 0x742c2c58, 0x2e1a1a34,
    0x2d1b1b36, 0xb26e6edc, 0xee5a5ab4, 0xfba0a05b,
    0xf65252a4, 0x4d3b3b76, 0x61d6d6b7, 0xceb3b37d,
    0x7b292952, 0x3ee3e3dd, 0x712f2f5e, 0x97848413,
    0xf55353a6, 0x68d1d1b9, 0x00000000, 0x2cededc1,
    0x60202040, 0x1ffcfce3, 0xc8b1b179, 0xed5b5bb6,
    0xbe6a6ad4, 0x46cbcb8d, 0xd9bebe67, 0x4b393972,
    0xde4a4a94, 0xd44c4c98, 0xe85858b0, 0x4acfcf85,
    0x6bd0d0bb, 0x2aefefc5, 0xe5aaaa4f, 0x16fbfbed,
    0xc5434386, 0xd74d4d9a, 0x55333366, 0x94858511,
    0xcf45458a, 0x10f9f9e9, 0x06020204, 0x817f7ffe,
    0xf05050a0, 0x443c3c78, 0xba9f9f25, 0xe3a8a84b,
    0xf35151a2, 0xfea3a35d, 0xc0404080, 0x8a8f8f05,
    0xad92923f, 0xbc9d9d21, 0x48383870, 0x04f5f5f1,
    0xdfbcbc63, 0xc1b6b677, 0x75dadaaf, 0x63212142,
    0x30101020, 0x1affffe5, 0x0ef3f3fd, 0x6dd2d2bf,
    0x4ccdcd81, 0x140c0c18, 0x35131326, 0x2fececc3,
    0xe15f5fbe, 0xa2979735, 0xcc444488, 0x3917172e,
    0x57c4c493, 0xf2a7a755, 0x827e7efc, 0x473d3d7a,
    0xac6464c8, 0xe75d5dba, 0x2b191932, 0x957373e6,
    0xa06060c0, 0x98818119, 0xd14f4f9e, 0x7fdcdca3,
    0x66222244, 0x7e2a2a54, 0xab90903b, 0x8388880b,
    0xca46468c, 0x29eeeec7, 0xd3b8b86b, 0x3c141428,
    0x79dedea7, 0xe25e5ebc, 0x1d0b0b16, 0x76dbdbad,
    0x3be0e0db, 0x56323264, 0x4e3a3a74, 0x1e0a0a14,
    0xdb494992, 0x0a06060c, 0x6c242448, 0xe45c5cb8,
    0x5dc2c29f, 0x6ed3d3bd, 0xefacac43, 0xa66262c4,
    0xa8919139, 0xa4959531, 0x37e4e4d3, 0x8b7979f2,
    0x32e7e7d5, 0x43c8c88b, 0x5937376e, 0xb76d6dda,
    0x8c8d8d01, 0x64d5d5b1, 0xd24e4e9c, 0xe0a9a949,
    0xb46c6cd8, 0xfa5656ac, 0x07f4f4f3, 0x25eaeacf,
    0xaf6565ca, 0x8e7a7af4, 0xe9aeae47, 0x18080810,
    0xd5baba6f, 0x887878f0, 0x6f25254a, 0x722e2e5c,
    0x241c1c38, 0xf1a6a657, 0xc7b4b473, 0x51c6c697,
    0x23e8e8cb, 0x7cdddda1, 0x9c7474e8, 0x211f1f3e,
    0xdd4b4b96, 0xdcbdbd61, 0x868b8b0d, 0x858a8a0f,
    0x907070e0, 0x423e3e7c, 0xc4b5b571, 0xaa6666cc,
    0xd8484890, 0x05030306, 0x01f6f6f7, 0x120e0e1c,
    0xa36161c2, 0x5f35356a, 0xf95757ae, 0xd0b9b969,
    0x91868617, 0x58c1c199, 0x271d1d3a, 0xb99e9e27,
    0x38e1e1d9, 0x13f8f8eb, 0xb398982b, 0x33111122,
    0xbb6969d2, 0x70d9d9a9, 0x898e8e07, 0xa7949433,
    0xb69b9b2d, 0x221e1e3c, 0x92878715, 0x20e9e9c9,
    0x49cece87, 0xff5555aa, 0x78282850, 0x7adfdfa5,
    0x8f8c8c03, 0xf8a1a159, 0x80898909, 0x170d0d1a,
    0xdabfbf65, 0x31e6e6d7, 0xc6424284, 0xb86868d0,
    0xc3414182, 0xb0999929, 0x772d2d5a, 0x110f0f1e,
    0xcbb0b07b, 0xfc5454a8, 0xd6bbbb6d, 0x3a16162c
static const struct
} dec_tables =
    }
static void prefetch_table(const volatile byte *tab, size_t len)
  for (i = 0; i < len; i += 8 * 32)
  prefetch_table((const void *)encT, sizeof(encT));
				       encT);
  return _gcry_aes_arm_encrypt_block(ctx->keyschenc, bx, ax, ctx->rounds, encT);
				       &dec_tables);
				     &dec_tables);

Fixed code:
/* Helper macro to force alignment to 16 or 64 bytes.  */
# define ATTR_ALIGNED_64  __attribute__ ((aligned (64)))
# define ATTR_ALIGNED_64
static struct
{
  volatile u32 counter_head;
  u32 cacheline_align[64 / 4 - 1];
  u32 T[256];
  volatile u32 counter_tail;
} enc_tables ATTR_ALIGNED_64 =
    0,
    { 0, },
    {
      0xa56363c6, 0x847c7cf8, 0x997777ee, 0x8d7b7bf6,
      0x0df2f2ff, 0xbd6b6bd6, 0xb16f6fde, 0x54c5c591,
      0x50303060, 0x03010102, 0xa96767ce, 0x7d2b2b56,
      0x19fefee7, 0x62d7d7b5, 0xe6abab4d, 0x9a7676ec,
      0x45caca8f, 0x9d82821f, 0x40c9c989, 0x877d7dfa,
      0x15fafaef, 0xeb5959b2, 0xc947478e, 0x0bf0f0fb,
      0xecadad41, 0x67d4d4b3, 0xfda2a25f, 0xeaafaf45,
      0xbf9c9c23, 0xf7a4a453, 0x967272e4, 0x5bc0c09b,
      0xc2b7b775, 0x1cfdfde1, 0xae93933d, 0x6a26264c,
      0x5a36366c, 0x413f3f7e, 0x02f7f7f5, 0x4fcccc83,
      0x5c343468, 0xf4a5a551, 0x34e5e5d1, 0x08f1f1f9,
      0x937171e2, 0x73d8d8ab, 0x53313162, 0x3f15152a,
      0x0c040408, 0x52c7c795, 0x65232346, 0x5ec3c39d,
      0x28181830, 0xa1969637, 0x0f05050a, 0xb59a9a2f,
      0x0907070e, 0x36121224, 0x9b80801b, 0x3de2e2df,
      0x26ebebcd, 0x6927274e, 0xcdb2b27f, 0x9f7575ea,
      0x1b090912, 0x9e83831d, 0x742c2c58, 0x2e1a1a34,
      0x2d1b1b36, 0xb26e6edc, 0xee5a5ab4, 0xfba0a05b,
      0xf65252a4, 0x4d3b3b76, 0x61d6d6b7, 0xceb3b37d,
      0x7b292952, 0x3ee3e3dd, 0x712f2f5e, 0x97848413,
      0xf55353a6, 0x68d1d1b9, 0x00000000, 0x2cededc1,
      0x60202040, 0x1ffcfce3, 0xc8b1b179, 0xed5b5bb6,
      0xbe6a6ad4, 0x46cbcb8d, 0xd9bebe67, 0x4b393972,
      0xde4a4a94, 0xd44c4c98, 0xe85858b0, 0x4acfcf85,
      0x6bd0d0bb, 0x2aefefc5, 0xe5aaaa4f, 0x16fbfbed,
      0xc5434386, 0xd74d4d9a, 0x55333366, 0x94858511,
      0xcf45458a, 0x10f9f9e9, 0x06020204, 0x817f7ffe,
      0xf05050a0, 0x443c3c78, 0xba9f9f25, 0xe3a8a84b,
      0xf35151a2, 0xfea3a35d, 0xc0404080, 0x8a8f8f05,
      0xad92923f, 0xbc9d9d21, 0x48383870, 0x04f5f5f1,
      0xdfbcbc63, 0xc1b6b677, 0x75dadaaf, 0x63212142,
      0x30101020, 0x1affffe5, 0x0ef3f3fd, 0x6dd2d2bf,
      0x4ccdcd81, 0x140c0c18, 0x35131326, 0x2fececc3,
      0xe15f5fbe, 0xa2979735, 0xcc444488, 0x3917172e,
      0x57c4c493, 0xf2a7a755, 0x827e7efc, 0x473d3d7a,
      0xac6464c8, 0xe75d5dba, 0x2b191932, 0x957373e6,
      0xa06060c0, 0x98818119, 0xd14f4f9e, 0x7fdcdca3,
      0x66222244, 0x7e2a2a54, 0xab90903b, 0x8388880b,
      0xca46468c, 0x29eeeec7, 0xd3b8b86b, 0x3c141428,
      0x79dedea7, 0xe25e5ebc, 0x1d0b0b16, 0x76dbdbad,
      0x3be0e0db, 0x56323264, 0x4e3a3a74, 0x1e0a0a14,
      0xdb494992, 0x0a06060c, 0x6c242448, 0xe45c5cb8,
      0x5dc2c29f, 0x6ed3d3bd, 0xefacac43, 0xa66262c4,
      0xa8919139, 0xa4959531, 0x37e4e4d3, 0x8b7979f2,
      0x32e7e7d5, 0x43c8c88b, 0x5937376e, 0xb76d6dda,
      0x8c8d8d01, 0x64d5d5b1, 0xd24e4e9c, 0xe0a9a949,
      0xb46c6cd8, 0xfa5656ac, 0x07f4f4f3, 0x25eaeacf,
      0xaf6565ca, 0x8e7a7af4, 0xe9aeae47, 0x18080810,
      0xd5baba6f, 0x887878f0, 0x6f25254a, 0x722e2e5c,
      0x241c1c38, 0xf1a6a657, 0xc7b4b473, 0x51c6c697,
      0x23e8e8cb, 0x7cdddda1, 0x9c7474e8, 0x211f1f3e,
      0xdd4b4b96, 0xdcbdbd61, 0x868b8b0d, 0x858a8a0f,
      0x907070e0, 0x423e3e7c, 0xc4b5b571, 0xaa6666cc,
      0xd8484890, 0x05030306, 0x01f6f6f7, 0x120e0e1c,
      0xa36161c2, 0x5f35356a, 0xf95757ae, 0xd0b9b969,
      0x91868617, 0x58c1c199, 0x271d1d3a, 0xb99e9e27,
      0x38e1e1d9, 0x13f8f8eb, 0xb398982b, 0x33111122,
      0xbb6969d2, 0x70d9d9a9, 0x898e8e07, 0xa7949433,
      0xb69b9b2d, 0x221e1e3c, 0x92878715, 0x20e9e9c9,
      0x49cece87, 0xff5555aa, 0x78282850, 0x7adfdfa5,
      0x8f8c8c03, 0xf8a1a159, 0x80898909, 0x170d0d1a,
      0xdabfbf65, 0x31e6e6d7, 0xc6424284, 0xb86868d0,
      0xc3414182, 0xb0999929, 0x772d2d5a, 0x110f0f1e,
      0xcbb0b07b, 0xfc5454a8, 0xd6bbbb6d, 0x3a16162c
    },
    0
#define encT enc_tables.T

static struct
  volatile u32 counter_head;
  u32 cacheline_align[64 / 4 - 1];
  volatile u32 counter_tail;
} dec_tables ATTR_ALIGNED_64 =
    0,
    { 0, },
    },
    0
static inline void prefetch_table(const volatile byte *tab, size_t len)
  for (i = 0; len - i >= 8 * 32; i += 8 * 32)
  for (; i < len; i += 32)
    {
      (void)tab[i];
    }
  /* Modify counters to trigger copy-on-write and unsharing if physical pages
   * of look-up table are shared between processes.  Modifying counters also
   * causes checksums for pages to change and hint same-page merging algorithm
   * that these pages are frequently changing.  */
  enc_tables.counter_head++;
  enc_tables.counter_tail++;

  /* Prefetch look-up tables to cache.  */
  prefetch_table((const void *)&enc_tables, sizeof(enc_tables));
  /* Modify counters to trigger copy-on-write and unsharing if physical pages
   * of look-up table are shared between processes.  Modifying counters also
   * causes checksums for pages to change and hint same-page merging algorithm
   * that these pages are frequently changing.  */
  dec_tables.counter_head++;
  dec_tables.counter_tail++;

  /* Prefetch look-up tables to cache.  */
				       enc_tables.T);
  return _gcry_aes_arm_encrypt_block(ctx->keyschenc, bx, ax, ctx->rounds,
				     enc_tables.T);
				       dec_tables.T);
				     dec_tables.T);