diff options
Diffstat (limited to 'src/lib/gssapi/krb5/k5sealv3.c')
| -rw-r--r-- | src/lib/gssapi/krb5/k5sealv3.c | 502 |
1 files changed, 502 insertions, 0 deletions
diff --git a/src/lib/gssapi/krb5/k5sealv3.c b/src/lib/gssapi/krb5/k5sealv3.c new file mode 100644 index 0000000..710c6f5 --- /dev/null +++ b/src/lib/gssapi/krb5/k5sealv3.c @@ -0,0 +1,502 @@ +/* + * lib/gssapi/krb5/k5sealv3.c + * + * Copyright 2003,2004 by the Massachusetts Institute of Technology. + * All Rights Reserved. + * + * Export of this software from the United States of America may + * require a specific license from the United States Government. + * It is the responsibility of any person or organization contemplating + * export to obtain such a license before exporting. + * + * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and + * distribute this software and its documentation for any purpose and + * without fee is hereby granted, provided that the above copyright + * notice appear in all copies and that both that copyright notice and + * this permission notice appear in supporting documentation, and that + * the name of M.I.T. not be used in advertising or publicity pertaining + * to distribution of the software without specific, written prior + * permission. Furthermore if you modify this software you must label + * your software as modified software and not distribute it in such a + * fashion that it might be confused with the original M.I.T. software. + * M.I.T. makes no representations about the suitability of + * this software for any purpose. It is provided "as is" without express + * or implied warranty. + * + * + */ +/* draft-ietf-krb-wg-gssapi-cfx-05 */ + +#include <assert.h> +#include "k5-platform.h" /* for 64-bit support */ +#include "k5-int.h" /* for zap() */ +#include "gssapiP_krb5.h" +#include <stdarg.h> + +static int +rotate_left (void *ptr, size_t bufsiz, size_t rc) +{ + /* Optimize for receiving. After some debugging is done, the MIT + implementation won't do any rotates on sending, and while + debugging, they'll be randomly chosen. + + Return 1 for success, 0 for failure (ENOMEM). */ + void *tbuf; + + if (bufsiz == 0) + return 1; + rc = rc % bufsiz; + if (rc == 0) + return 1; + + tbuf = malloc(rc); + if (tbuf == 0) + return 0; + memcpy(tbuf, ptr, rc); + memmove(ptr, (char *)ptr + rc, bufsiz - rc); + memcpy((char *)ptr + bufsiz - rc, tbuf, rc); + free(tbuf); + return 1; +} + +static const gss_buffer_desc empty_message = { 0, 0 }; + +#define FLAG_SENDER_IS_ACCEPTOR 0x01 +#define FLAG_WRAP_CONFIDENTIAL 0x02 +#define FLAG_ACCEPTOR_SUBKEY 0x04 + +krb5_error_code +gss_krb5int_make_seal_token_v3 (krb5_context context, + krb5_gss_ctx_id_rec *ctx, + const gss_buffer_desc * message, + gss_buffer_t token, + int conf_req_flag, int toktype) +{ + size_t bufsize = 16; + unsigned char *outbuf = 0; + krb5_error_code err; + int key_usage; + unsigned char acceptor_flag; + const gss_buffer_desc *message2 = message; + size_t rrc, ec; + unsigned short tok_id; + krb5_checksum sum; + krb5_keyblock *key; + + assert(toktype != KG_TOK_SEAL_MSG || ctx->enc != 0); + assert(ctx->big_endian == 0); + + acceptor_flag = ctx->initiate ? 0 : FLAG_SENDER_IS_ACCEPTOR; + key_usage = (toktype == KG_TOK_WRAP_MSG + ? (ctx->initiate + ? KG_USAGE_INITIATOR_SEAL + : KG_USAGE_ACCEPTOR_SEAL) + : (ctx->initiate + ? KG_USAGE_INITIATOR_SIGN + : KG_USAGE_ACCEPTOR_SIGN)); + if (ctx->have_acceptor_subkey) { + key = ctx->acceptor_subkey; + } else { + key = ctx->enc; + } + +#ifdef CFX_EXERCISE + { + static int initialized = 0; + if (!initialized) { + srand(time(0)); + initialized = 1; + } + } +#endif + + if (toktype == KG_TOK_WRAP_MSG && conf_req_flag) { + krb5_data plain; + krb5_enc_data cipher; + size_t ec_max; + + /* 300: Adds some slop. */ + if (SIZE_MAX - 300 < message->length) + return ENOMEM; + ec_max = SIZE_MAX - message->length - 300; + if (ec_max > 0xffff) + ec_max = 0xffff; +#ifdef CFX_EXERCISE + /* For testing only. For performance, always set ec = 0. */ + ec = ec_max & rand(); +#else + ec = 0; +#endif + plain.length = message->length + 16 + ec; + plain.data = malloc(message->length + 16 + ec); + if (plain.data == NULL) + return ENOMEM; + + /* Get size of ciphertext. */ + bufsize = 16 + krb5_encrypt_size (plain.length, ctx->enc->enctype); + /* Allocate space for header plus encrypted data. */ + outbuf = malloc(bufsize); + if (outbuf == NULL) { + free(plain.data); + return ENOMEM; + } + + /* TOK_ID */ + store_16_be(0x0504, outbuf); + /* flags */ + outbuf[2] = (acceptor_flag + | (conf_req_flag ? FLAG_WRAP_CONFIDENTIAL : 0) + | (ctx->have_acceptor_subkey ? FLAG_ACCEPTOR_SUBKEY : 0)); + /* filler */ + outbuf[3] = 0xff; + /* EC */ + store_16_be(ec, outbuf+4); + /* RRC */ + store_16_be(0, outbuf+6); + store_64_be(ctx->seq_send, outbuf+8); + + memcpy(plain.data, message->value, message->length); + memset(plain.data + message->length, 'x', ec); + memcpy(plain.data + message->length + ec, outbuf, 16); + + cipher.ciphertext.data = outbuf + 16; + cipher.ciphertext.length = bufsize - 16; + cipher.enctype = key->enctype; + err = krb5_c_encrypt(context, key, key_usage, 0, &plain, &cipher); + zap(plain.data, plain.length); + free(plain.data); + plain.data = 0; + if (err) + goto error; + + /* Now that we know we're returning a valid token.... */ + ctx->seq_send++; + +#ifdef CFX_EXERCISE + rrc = rand() & 0xffff; + if (rotate_left(outbuf+16, bufsize-16, + (bufsize-16) - (rrc % (bufsize - 16)))) + store_16_be(rrc, outbuf+6); + /* If the rotate fails, don't worry about it. */ +#endif + } else if (toktype == KG_TOK_WRAP_MSG && !conf_req_flag) { + krb5_data plain; + + /* Here, message is the application-supplied data; message2 is + what goes into the output token. They may be the same, or + message2 may be empty (for MIC). */ + + tok_id = 0x0504; + + wrap_with_checksum: + plain.length = message->length + 16; + plain.data = malloc(message->length + 16); + if (plain.data == NULL) + return ENOMEM; + + if (ctx->cksum_size > 0xffff) + abort(); + + bufsize = 16 + message2->length + ctx->cksum_size; + outbuf = malloc(bufsize); + if (outbuf == NULL) { + free(plain.data); + plain.data = 0; + err = ENOMEM; + goto error; + } + + /* TOK_ID */ + store_16_be(tok_id, outbuf); + /* flags */ + outbuf[2] = (acceptor_flag + | (ctx->have_acceptor_subkey ? FLAG_ACCEPTOR_SUBKEY : 0)); + /* filler */ + outbuf[3] = 0xff; + if (toktype == KG_TOK_WRAP_MSG) { + /* Use 0 for checksum calculation, substitute + checksum length later. */ + /* EC */ + store_16_be(0, outbuf+4); + /* RRC */ + store_16_be(0, outbuf+6); + } else { + /* MIC and DEL store 0xFF in EC and RRC. */ + store_16_be(0xffff, outbuf+4); + store_16_be(0xffff, outbuf+6); + } + store_64_be(ctx->seq_send, outbuf+8); + + memcpy(plain.data, message->value, message->length); + memcpy(plain.data + message->length, outbuf, 16); + + /* Fill in the output token -- data contents, if any, and + space for the checksum. */ + if (message2->length) + memcpy(outbuf + 16, message2->value, message2->length); + + sum.contents = outbuf + 16 + message2->length; + sum.length = ctx->cksum_size; + + err = krb5_c_make_checksum(context, ctx->cksumtype, key, + key_usage, &plain, &sum); + zap(plain.data, plain.length); + free(plain.data); + plain.data = 0; + if (err) { + zap(outbuf,bufsize); + free(outbuf); + goto error; + } + if (sum.length != ctx->cksum_size) + abort(); + memcpy(outbuf + 16 + message2->length, sum.contents, ctx->cksum_size); + krb5_free_checksum_contents(context, &sum); + sum.contents = 0; + /* Now that we know we're actually generating the token... */ + ctx->seq_send++; + + if (toktype == KG_TOK_WRAP_MSG) { +#ifdef CFX_EXERCISE + rrc = rand() & 0xffff; + /* If the rotate fails, don't worry about it. */ + if (rotate_left(outbuf+16, bufsize-16, + (bufsize-16) - (rrc % (bufsize - 16)))) + store_16_be(rrc, outbuf+6); +#endif + /* Fix up EC field. */ + store_16_be(ctx->cksum_size, outbuf+4); + } else { + store_16_be(0xffff, outbuf+6); + } + } else if (toktype == KG_TOK_MIC_MSG) { + tok_id = 0x0404; + message2 = &empty_message; + goto wrap_with_checksum; + } else if (toktype == KG_TOK_DEL_CTX) { + tok_id = 0x0405; + message = message2 = &empty_message; + goto wrap_with_checksum; + } else + abort(); + + token->value = outbuf; + token->length = bufsize; + return 0; + +error: + free(outbuf); + token->value = NULL; + token->length = 0; + return err; +} + +/* message_buffer is an input if SIGN, output if SEAL, and ignored if DEL_CTX + conf_state is only valid if SEAL. */ + +OM_uint32 +gss_krb5int_unseal_token_v3(krb5_context *contextptr, + OM_uint32 *minor_status, + krb5_gss_ctx_id_rec *ctx, + unsigned char *ptr, int bodysize, + gss_buffer_t message_buffer, + int *conf_state, int *qop_state, int toktype) +{ + krb5_context context = *contextptr; + krb5_data plain; + gssint_uint64 seqnum; + size_t ec, rrc; + int key_usage; + unsigned char acceptor_flag; + krb5_checksum sum; + krb5_error_code err; + krb5_boolean valid; + krb5_keyblock *key; + + assert(toktype != KG_TOK_SEAL_MSG || ctx->enc != 0); + assert(ctx->big_endian == 0); + assert(ctx->proto == 1); + + if (qop_state) + *qop_state = GSS_C_QOP_DEFAULT; + + acceptor_flag = ctx->initiate ? FLAG_SENDER_IS_ACCEPTOR : 0; + key_usage = (toktype == KG_TOK_WRAP_MSG + ? (!ctx->initiate + ? KG_USAGE_INITIATOR_SEAL + : KG_USAGE_ACCEPTOR_SEAL) + : (!ctx->initiate + ? KG_USAGE_INITIATOR_SIGN + : KG_USAGE_ACCEPTOR_SIGN)); + + /* Oops. I wrote this code assuming ptr would be at the start of + the token header. */ + ptr -= 2; + bodysize += 2; + + if (bodysize < 16) { + defective: + *minor_status = 0; + return GSS_S_DEFECTIVE_TOKEN; + } + if ((ptr[2] & FLAG_SENDER_IS_ACCEPTOR) != acceptor_flag) { + *minor_status = G_BAD_DIRECTION; + return GSS_S_BAD_SIG; + } + + /* Two things to note here. + + First, we can't really enforce the use of the acceptor's subkey, + if we're the acceptor; the initiator may have sent messages + before getting the subkey. We could probably enforce it if + we're the initiator. + + Second, if someone tweaks the code to not set the flag telling + the krb5 library to generate a new subkey in the AP-REP + message, the MIT library may include a subkey anyways -- + namely, a copy of the AP-REQ subkey, if it was provided. So + the initiator may think we wanted a subkey, and set the flag, + even though we weren't trying to set the subkey. The "other" + key, the one not asserted by the acceptor, will have the same + value in that case, though, so we can just ignore the flag. */ + if (ctx->have_acceptor_subkey && (ptr[2] & FLAG_ACCEPTOR_SUBKEY)) { + key = ctx->acceptor_subkey; + } else { + key = ctx->enc; + } + + if (toktype == KG_TOK_WRAP_MSG) { + if (load_16_be(ptr) != 0x0504) + goto defective; + if (ptr[3] != 0xff) + goto defective; + ec = load_16_be(ptr+4); + rrc = load_16_be(ptr+6); + seqnum = load_64_be(ptr+8); + if (!rotate_left(ptr+16, bodysize-16, rrc)) { + no_mem: + *minor_status = ENOMEM; + return GSS_S_FAILURE; + } + if (ptr[2] & FLAG_WRAP_CONFIDENTIAL) { + /* confidentiality */ + krb5_enc_data cipher; + unsigned char *althdr; + + if (conf_state) + *conf_state = 1; + /* Do we have no decrypt_size function? + + For all current cryptosystems, the ciphertext size will + be larger than the plaintext size. */ + cipher.enctype = key->enctype; + cipher.ciphertext.length = bodysize - 16; + cipher.ciphertext.data = ptr + 16; + plain.length = bodysize - 16; + plain.data = malloc(plain.length); + if (plain.data == NULL) + goto no_mem; + err = krb5_c_decrypt(context, key, key_usage, 0, + &cipher, &plain); + if (err) { + free(plain.data); + goto error; + } + /* Don't use bodysize here! Use the fact that + cipher.ciphertext.length has been adjusted to the + correct length. */ + althdr = plain.data + plain.length - 16; + if (load_16_be(althdr) != 0x0504 + || althdr[2] != ptr[2] + || althdr[3] != ptr[3] + || memcmp(althdr+8, ptr+8, 8)) + goto defective; + message_buffer->value = plain.data; + message_buffer->length = plain.length - ec - 16; + } else { + /* no confidentiality */ + if (conf_state) + *conf_state = 0; + if (ec + 16 < ec) + /* overflow check */ + goto defective; + if (ec + 16 > bodysize) + goto defective; + /* We have: header | msg | cksum. + We need cksum(msg | header). + Rotate the first two. */ + store_16_be(0, ptr+4); + store_16_be(0, ptr+6); + plain.length = bodysize-ec; + plain.data = ptr; + if (!rotate_left(ptr, bodysize-ec, 16)) + goto no_mem; + sum.length = ec; + if (sum.length != ctx->cksum_size) { + *minor_status = 0; + return GSS_S_BAD_SIG; + } + sum.contents = ptr+bodysize-ec; + sum.checksum_type = ctx->cksumtype; + err = krb5_c_verify_checksum(context, key, key_usage, + &plain, &sum, &valid); + if (err) + goto error; + if (!valid) { + *minor_status = 0; + return GSS_S_BAD_SIG; + } + message_buffer->length = plain.length - 16; + message_buffer->value = malloc(message_buffer->length); + if (message_buffer->value == NULL) + goto no_mem; + memcpy(message_buffer->value, plain.data, message_buffer->length); + } + err = g_order_check(&ctx->seqstate, seqnum); + *minor_status = 0; + return err; + } else if (toktype == KG_TOK_MIC_MSG) { + /* wrap token, no confidentiality */ + if (load_16_be(ptr) != 0x0404) + goto defective; + verify_mic_1: + if (ptr[3] != 0xff) + goto defective; + if (load_32_be(ptr+4) != 0xffffffffL) + goto defective; + seqnum = load_64_be(ptr+8); + plain.length = message_buffer->length + 16; + plain.data = malloc(plain.length); + if (plain.data == NULL) + goto no_mem; + if (message_buffer->length) + memcpy(plain.data, message_buffer->value, message_buffer->length); + memcpy(plain.data + message_buffer->length, ptr, 16); + sum.length = bodysize - 16; + sum.contents = ptr + 16; + sum.checksum_type = ctx->cksumtype; + err = krb5_c_verify_checksum(context, key, key_usage, + &plain, &sum, &valid); + if (err) { + error: + free(plain.data); + *minor_status = err; + return GSS_S_BAD_SIG; /* XXX */ + } + if (!valid) { + free(plain.data); + *minor_status = 0; + return GSS_S_BAD_SIG; + } + err = g_order_check(&ctx->seqstate, seqnum); + *minor_status = 0; + return err; + } else if (toktype == KG_TOK_DEL_CTX) { + if (load_16_be(ptr) != 0x0405) + goto defective; + message_buffer = &empty_message; + goto verify_mic_1; + } else { + goto defective; + } +} |