From 99a6ec6bd6a1c73753710b33743206e9e05dc172 Mon Sep 17 00:00:00 2001 From: Joseph Sutton Date: Tue, 25 Oct 2022 16:58:55 -0500 Subject: [PATCH] krb5: CVE-2022-42898 PAC parse integer overflows Catch overflows that result from adding PAC_INFO_BUFFER_SIZE. Samba BUG: https://bugzilla.samba.org/show_bug.cgi?id=15203 Signed-off-by: Nico Williams --- lib/krb5/pac.c | 178 +++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 150 insertions(+), 28 deletions(-) diff --git a/lib/krb5/pac.c b/lib/krb5/pac.c index c26201be9cd7..cf051cd1f1f4 100644 --- a/lib/krb5/pac.c +++ b/lib/krb5/pac.c @@ -112,6 +112,56 @@ HMAC_MD5_any_checksum(krb5_context context, } +static krb5_error_code pac_header_size(krb5_context context, + uint32_t num_buffers, + uint32_t *result) +{ + krb5_error_code ret; + uint32_t header_size; + + /* Guard against integer overflow on 32-bit systems. */ + if (num_buffers > 1000) { + ret = EINVAL; + krb5_set_error_message(context, ret, "PAC has too many buffers"); + return ret; + } + header_size = PAC_INFO_BUFFER_SIZE * num_buffers; + + /* Guard against integer overflow on 32-bit systems. */ + if (header_size > UINT32_MAX - PACTYPE_SIZE) { + ret = EINVAL; + krb5_set_error_message(context, ret, "PAC has too many buffers"); + return ret; + } + header_size += PACTYPE_SIZE; + + *result = header_size; + + return 0; +} + +static krb5_error_code pac_aligned_size(krb5_context context, + uint32_t size, + uint32_t *aligned_size) +{ + krb5_error_code ret; + + /* Guard against integer overflow on 32-bit systems. */ + if (size > UINT32_MAX - (PAC_ALIGNMENT - 1)) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + return ret; + } + size += PAC_ALIGNMENT - 1; + + /* align to PAC_ALIGNMENT */ + size = (size / PAC_ALIGNMENT) * PAC_ALIGNMENT; + + *aligned_size = size; + + return 0; +} + /* * */ @@ -153,8 +203,12 @@ krb5_pac_parse(krb5_context context, const void *ptr, size_t len, goto out; } - p->pac = calloc(1, - sizeof(*p->pac) + (sizeof(p->pac->buffers[0]) * (tmp - 1))); + ret = pac_header_size(context, tmp, &header_end); + if (ret) { + return ret; + } + + p->pac = calloc(1, header_end); if (p->pac == NULL) { ret = krb5_enomem(context); goto out; @@ -163,7 +217,6 @@ krb5_pac_parse(krb5_context context, const void *ptr, size_t len, p->pac->numbuffers = tmp; p->pac->version = tmp2; - header_end = PACTYPE_SIZE + (PAC_INFO_BUFFER_SIZE * p->pac->numbuffers); if (header_end > len) { ret = EINVAL; goto out; @@ -292,37 +345,65 @@ krb5_pac_add_buffer(krb5_context context, krb5_pac p, { krb5_error_code ret; void *ptr; - size_t len, offset, header_end, old_end; + uint32_t unaligned_len, num_buffers, len, offset, header_end, old_end; uint32_t i; - len = p->pac->numbuffers; + if (data->length > UINT32_MAX) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + return ret; + } + + num_buffers = p->pac->numbuffers; + + if (num_buffers >= UINT32_MAX) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + return ret; + } + ret = pac_header_size(context, num_buffers + 1, &header_end); + if (ret) { + return ret; + } - ptr = realloc(p->pac, - sizeof(*p->pac) + (sizeof(p->pac->buffers[0]) * len)); + ptr = realloc(p->pac, header_end); if (ptr == NULL) return krb5_enomem(context); p->pac = ptr; - for (i = 0; i < len; i++) + for (i = 0; i < num_buffers; i++) { + if (p->pac->buffers[i].offset_lo > UINT32_MAX - PAC_INFO_BUFFER_SIZE) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + return ret; + } + p->pac->buffers[i].offset_lo += PAC_INFO_BUFFER_SIZE; + } + if (p->data.length > UINT32_MAX - PAC_INFO_BUFFER_SIZE) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + return ret; + } offset = p->data.length + PAC_INFO_BUFFER_SIZE; - p->pac->buffers[len].type = type; - p->pac->buffers[len].buffersize = data->length; - p->pac->buffers[len].offset_lo = offset; - p->pac->buffers[len].offset_hi = 0; + p->pac->buffers[num_buffers].type = type; + p->pac->buffers[num_buffers].buffersize = data->length; + p->pac->buffers[num_buffers].offset_lo = offset; + p->pac->buffers[num_buffers].offset_hi = 0; old_end = p->data.length; - len = p->data.length + data->length + PAC_INFO_BUFFER_SIZE; - if (len < p->data.length) { + if (offset > UINT32_MAX - data->length) { krb5_set_error_message(context, EINVAL, "integer overrun"); return EINVAL; } + unaligned_len = offset + data->length; - /* align to PAC_ALIGNMENT */ - len = ((len + PAC_ALIGNMENT - 1) / PAC_ALIGNMENT) * PAC_ALIGNMENT; + ret = pac_aligned_size(context, unaligned_len, &len); + if (ret) + return ret; ret = krb5_data_realloc(&p->data, len); if (ret) { @@ -333,7 +414,7 @@ krb5_pac_add_buffer(krb5_context context, krb5_pac p, /* * make place for new PAC INFO BUFFER header */ - header_end = PACTYPE_SIZE + (PAC_INFO_BUFFER_SIZE * p->pac->numbuffers); + header_end -= PAC_INFO_BUFFER_SIZE; memmove((unsigned char *)p->data.data + header_end + PAC_INFO_BUFFER_SIZE, (unsigned char *)p->data.data + header_end , old_end - header_end); @@ -346,7 +427,7 @@ krb5_pac_add_buffer(krb5_context context, krb5_pac p, memcpy((unsigned char *)p->data.data + offset, data->data, data->length); memset((unsigned char *)p->data.data + offset + data->length, - 0, p->data.length - offset - data->length); + 0, p->data.length - unaligned_len); p->pac->numbuffers += 1; @@ -375,8 +456,8 @@ krb5_pac_get_buffer(krb5_context context, krb5_pac p, uint32_t i; for (i = 0; i < p->pac->numbuffers; i++) { - const size_t len = p->pac->buffers[i].buffersize; - const size_t offset = p->pac->buffers[i].offset_lo; + const uint32_t len = p->pac->buffers[i].buffersize; + const uint32_t offset = p->pac->buffers[i].offset_lo; if (p->pac->buffers[i].type != type) continue; @@ -981,8 +1062,8 @@ _krb5_pac_sign(krb5_context context, size_t server_size, priv_size; uint32_t server_offset = 0, priv_offset = 0; uint32_t server_cksumtype = 0, priv_cksumtype = 0; - int num = 0; - size_t i; + uint32_t num = 0; + uint32_t i; krb5_data logon, d; krb5_data_zero(&logon); @@ -1030,8 +1111,18 @@ _krb5_pac_sign(krb5_context context, if (num) { void *ptr; - - ptr = realloc(p->pac, sizeof(*p->pac) + (sizeof(p->pac->buffers[0]) * (p->pac->numbuffers + num - 1))); + uint32_t len; + + if (p->pac->numbuffers > UINT32_MAX - num) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + goto out; + } + ret = pac_header_size(context, p->pac->numbuffers + num, &len); + if (ret) + goto out; + + ptr = realloc(p->pac, len); if (ptr == NULL) return krb5_enomem(context); @@ -1084,7 +1175,9 @@ _krb5_pac_sign(krb5_context context, CHECK(ret, krb5_store_uint32(sp, p->pac->numbuffers), out); CHECK(ret, krb5_store_uint32(sp, p->pac->version), out); - end = PACTYPE_SIZE + (PAC_INFO_BUFFER_SIZE * p->pac->numbuffers); + ret = pac_header_size(context, p->pac->numbuffers, &end); + if (ret) + goto out; for (i = 0; i < p->pac->numbuffers; i++) { uint32_t len; @@ -1094,11 +1187,31 @@ _krb5_pac_sign(krb5_context context, /* store data */ if (p->pac->buffers[i].type == PAC_SERVER_CHECKSUM) { + if (server_size > UINT32_MAX - 4) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + goto out; + } + if (end > UINT32_MAX - 4) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + goto out; + } len = server_size + 4; server_offset = end + 4; CHECK(ret, krb5_store_uint32(spdata, server_cksumtype), out); CHECK(ret, fill_zeros(context, spdata, server_size), out); } else if (p->pac->buffers[i].type == PAC_PRIVSVR_CHECKSUM) { + if (priv_size > UINT32_MAX - 4) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + goto out; + } + if (end > UINT32_MAX - 4) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + goto out; + } len = priv_size + 4; priv_offset = end + 4; CHECK(ret, krb5_store_uint32(spdata, priv_cksumtype), out); @@ -1129,11 +1242,20 @@ _krb5_pac_sign(krb5_context context, /* advance data endpointer and align */ { - int32_t e; + uint32_t e; + if (end > UINT32_MAX - len) { + ret = EINVAL; + krb5_set_error_message(context, ret, "integer overrun"); + goto out; + } end += len; - e = ((end + PAC_ALIGNMENT - 1) / PAC_ALIGNMENT) * PAC_ALIGNMENT; - if ((int32_t)end != e) { + + ret = pac_aligned_size(context, end, &e); + if (ret) + goto out; + + if (end != e) { CHECK(ret, fill_zeros(context, spdata, e - end), out); } end = e; -- 2.38.1