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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#include <linux/export.h>#include <linux/kernel.h>#include <linux/errno.h>#include <linux/module.h>#include <linux/asn1_decoder.h>#include <linux/asn1_ber_bytecode.h>
static const unsigned char asn1_op_lengths[ASN1_OP__NR] = { /* OPC TAG JMP ACT */ [ASN1_OP_MATCH] = 1 + 1, [ASN1_OP_MATCH_OR_SKIP] = 1 + 1, [ASN1_OP_MATCH_ACT] = 1 + 1 + 1, [ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1, [ASN1_OP_MATCH_JUMP] = 1 + 1 + 1, [ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1, [ASN1_OP_MATCH_ANY] = 1, [ASN1_OP_MATCH_ANY_OR_SKIP] = 1, [ASN1_OP_MATCH_ANY_ACT] = 1 + 1, [ASN1_OP_MATCH_ANY_ACT_OR_SKIP] = 1 + 1, [ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1, [ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1, [ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1, [ASN1_OP_COND_MATCH_ANY] = 1, [ASN1_OP_COND_MATCH_ANY_OR_SKIP] = 1, [ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1, [ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP] = 1 + 1, [ASN1_OP_COND_FAIL] = 1, [ASN1_OP_COMPLETE] = 1, [ASN1_OP_ACT] = 1 + 1, [ASN1_OP_MAYBE_ACT] = 1 + 1, [ASN1_OP_RETURN] = 1, [ASN1_OP_END_SEQ] = 1, [ASN1_OP_END_SEQ_OF] = 1 + 1, [ASN1_OP_END_SET] = 1, [ASN1_OP_END_SET_OF] = 1 + 1, [ASN1_OP_END_SEQ_ACT] = 1 + 1, [ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1, [ASN1_OP_END_SET_ACT] = 1 + 1, [ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,};
/* * Find the length of an indefinite length object * @data: The data buffer * @datalen: The end of the innermost containing element in the buffer * @_dp: The data parse cursor (updated before returning) * @_len: Where to return the size of the element. * @_errmsg: Where to return a pointer to an error message on error */static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen, size_t *_dp, size_t *_len, const char **_errmsg){ unsigned char tag, tmp; size_t dp = *_dp, len, n; int indef_level = 1;
next_tag: if (unlikely(datalen - dp < 2)) { if (datalen == dp) goto missing_eoc; goto data_overrun_error; }
/* Extract a tag from the data */ tag = data[dp++]; if (tag == ASN1_EOC) { /* It appears to be an EOC. */ if (data[dp++] != 0) goto invalid_eoc; if (--indef_level <= 0) { *_len = dp - *_dp; *_dp = dp; return 0; } goto next_tag; }
if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) { do { if (unlikely(datalen - dp < 2)) goto data_overrun_error; tmp = data[dp++]; } while (tmp & 0x80); }
/* Extract the length */ len = data[dp++]; if (len <= 0x7f) goto check_length;
if (unlikely(len == ASN1_INDEFINITE_LENGTH)) { /* Indefinite length */ if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5)) goto indefinite_len_primitive; indef_level++; goto next_tag; }
n = len - 0x80; if (unlikely(n > sizeof(len) - 1)) goto length_too_long; if (unlikely(n > datalen - dp)) goto data_overrun_error; len = 0; for (; n > 0; n--) { len <<= 8; len |= data[dp++]; }check_length: if (len > datalen - dp) goto data_overrun_error; dp += len; goto next_tag;
length_too_long: *_errmsg = "Unsupported length"; goto error;indefinite_len_primitive: *_errmsg = "Indefinite len primitive not permitted"; goto error;invalid_eoc: *_errmsg = "Invalid length EOC"; goto error;data_overrun_error: *_errmsg = "Data overrun error"; goto error;missing_eoc: *_errmsg = "Missing EOC in indefinite len cons";error: *_dp = dp; return -1;}
/** * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern * @decoder: The decoder definition (produced by asn1_compiler) * @context: The caller's context (to be passed to the action functions) * @data: The encoded data * @datalen: The size of the encoded data * * Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern * produced by asn1_compiler. Action functions are called on marked tags to * allow the caller to retrieve significant data. * * LIMITATIONS: * * To keep down the amount of stack used by this function, the following limits * have been imposed: * * (1) This won't handle datalen > 65535 without increasing the size of the * cons stack elements and length_too_long checking. * * (2) The stack of constructed types is 10 deep. If the depth of non-leaf * constructed types exceeds this, the decode will fail. * * (3) The SET type (not the SET OF type) isn't really supported as tracking * what members of the set have been seen is a pain. */int asn1_ber_decoder(const struct asn1_decoder *decoder, void *context, const unsigned char *data, size_t datalen){ const unsigned char *machine = decoder->machine; const asn1_action_t *actions = decoder->actions; size_t machlen = decoder->machlen; enum asn1_opcode op; unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0; const char *errmsg; size_t pc = 0, dp = 0, tdp = 0, len = 0; int ret;
unsigned char flags = 0;#define FLAG_INDEFINITE_LENGTH 0x01#define FLAG_MATCHED 0x02#define FLAG_LAST_MATCHED 0x04 /* Last tag matched */#define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag * - ie. whether or not we are going to parse * a compound type. */
#define NR_CONS_STACK 10 unsigned short cons_dp_stack[NR_CONS_STACK]; unsigned short cons_datalen_stack[NR_CONS_STACK]; unsigned char cons_hdrlen_stack[NR_CONS_STACK];#define NR_JUMP_STACK 10 unsigned char jump_stack[NR_JUMP_STACK];
if (datalen > 65535) return -EMSGSIZE;
next_op: pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n", pc, machlen, dp, datalen, csp, jsp); if (unlikely(pc >= machlen)) goto machine_overrun_error; op = machine[pc]; if (unlikely(pc + asn1_op_lengths[op] > machlen)) goto machine_overrun_error;
/* If this command is meant to match a tag, then do that before * evaluating the command. */ if (op <= ASN1_OP__MATCHES_TAG) { unsigned char tmp;
/* Skip conditional matches if possible */ if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) || (op & ASN1_OP_MATCH__SKIP && dp == datalen)) { flags &= ~FLAG_LAST_MATCHED; pc += asn1_op_lengths[op]; goto next_op; }
flags = 0; hdr = 2;
/* Extract a tag from the data */ if (unlikely(datalen - dp < 2)) goto data_overrun_error; tag = data[dp++]; if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) goto long_tag_not_supported;
if (op & ASN1_OP_MATCH__ANY) { pr_debug("- any %02x\n", tag); } else { /* Extract the tag from the machine * - Either CONS or PRIM are permitted in the data if * CONS is not set in the op stream, otherwise CONS * is mandatory. */ optag = machine[pc + 1]; flags |= optag & FLAG_CONS;
/* Determine whether the tag matched */ tmp = optag ^ tag; tmp &= ~(optag & ASN1_CONS_BIT); pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp); if (tmp != 0) { /* All odd-numbered tags are MATCH_OR_SKIP. */ if (op & ASN1_OP_MATCH__SKIP) { pc += asn1_op_lengths[op]; dp--; goto next_op; } goto tag_mismatch; } } flags |= FLAG_MATCHED;
len = data[dp++]; if (len > 0x7f) { if (unlikely(len == ASN1_INDEFINITE_LENGTH)) { /* Indefinite length */ if (unlikely(!(tag & ASN1_CONS_BIT))) goto indefinite_len_primitive; flags |= FLAG_INDEFINITE_LENGTH; if (unlikely(2 > datalen - dp)) goto data_overrun_error; } else { int n = len - 0x80; if (unlikely(n > 2)) goto length_too_long; if (unlikely(n > datalen - dp)) goto data_overrun_error; hdr += n; for (len = 0; n > 0; n--) { len <<= 8; len |= data[dp++]; } if (unlikely(len > datalen - dp)) goto data_overrun_error; } } else { if (unlikely(len > datalen - dp)) goto data_overrun_error; }
if (flags & FLAG_CONS) { /* For expected compound forms, we stack the positions * of the start and end of the data. */ if (unlikely(csp >= NR_CONS_STACK)) goto cons_stack_overflow; cons_dp_stack[csp] = dp; cons_hdrlen_stack[csp] = hdr; if (!(flags & FLAG_INDEFINITE_LENGTH)) { cons_datalen_stack[csp] = datalen; datalen = dp + len; } else { cons_datalen_stack[csp] = 0; } csp++; }
pr_debug("- TAG: %02x %zu%s\n", tag, len, flags & FLAG_CONS ? " CONS" : ""); tdp = dp; }
/* Decide how to handle the operation */ switch (op) { case ASN1_OP_MATCH: case ASN1_OP_MATCH_OR_SKIP: case ASN1_OP_MATCH_ACT: case ASN1_OP_MATCH_ACT_OR_SKIP: case ASN1_OP_MATCH_ANY: case ASN1_OP_MATCH_ANY_OR_SKIP: case ASN1_OP_MATCH_ANY_ACT: case ASN1_OP_MATCH_ANY_ACT_OR_SKIP: case ASN1_OP_COND_MATCH_OR_SKIP: case ASN1_OP_COND_MATCH_ACT_OR_SKIP: case ASN1_OP_COND_MATCH_ANY: case ASN1_OP_COND_MATCH_ANY_OR_SKIP: case ASN1_OP_COND_MATCH_ANY_ACT: case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
if (!(flags & FLAG_CONS)) { if (flags & FLAG_INDEFINITE_LENGTH) { size_t tmp = dp;
ret = asn1_find_indefinite_length( data, datalen, &tmp, &len, &errmsg); if (ret < 0) goto error; } pr_debug("- LEAF: %zu\n", len); }
if (op & ASN1_OP_MATCH__ACT) { unsigned char act;
if (op & ASN1_OP_MATCH__ANY) act = machine[pc + 1]; else act = machine[pc + 2]; ret = actions[act](context, hdr, tag, data + dp, len); if (ret < 0) return ret; }
if (!(flags & FLAG_CONS)) dp += len; pc += asn1_op_lengths[op]; goto next_op;
case ASN1_OP_MATCH_JUMP: case ASN1_OP_MATCH_JUMP_OR_SKIP: case ASN1_OP_COND_MATCH_JUMP_OR_SKIP: pr_debug("- MATCH_JUMP\n"); if (unlikely(jsp == NR_JUMP_STACK)) goto jump_stack_overflow; jump_stack[jsp++] = pc + asn1_op_lengths[op]; pc = machine[pc + 2]; goto next_op;
case ASN1_OP_COND_FAIL: if (unlikely(!(flags & FLAG_MATCHED))) goto tag_mismatch; pc += asn1_op_lengths[op]; goto next_op;
case ASN1_OP_COMPLETE: if (unlikely(jsp != 0 || csp != 0)) { pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n", jsp, csp); return -EBADMSG; } return 0;
case ASN1_OP_END_SET: case ASN1_OP_END_SET_ACT: if (unlikely(!(flags & FLAG_MATCHED))) goto tag_mismatch; fallthrough;
case ASN1_OP_END_SEQ: case ASN1_OP_END_SET_OF: case ASN1_OP_END_SEQ_OF: case ASN1_OP_END_SEQ_ACT: case ASN1_OP_END_SET_OF_ACT: case ASN1_OP_END_SEQ_OF_ACT: if (unlikely(csp <= 0)) goto cons_stack_underflow; csp--; tdp = cons_dp_stack[csp]; hdr = cons_hdrlen_stack[csp]; len = datalen; datalen = cons_datalen_stack[csp]; pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n", tdp, dp, len, datalen); if (datalen == 0) { /* Indefinite length - check for the EOC. */ datalen = len; if (unlikely(datalen - dp < 2)) goto data_overrun_error; if (data[dp++] != 0) { if (op & ASN1_OP_END__OF) { dp--; csp++; pc = machine[pc + 1]; pr_debug("- continue\n"); goto next_op; } goto missing_eoc; } if (data[dp++] != 0) goto invalid_eoc; len = dp - tdp - 2; } else { if (dp < len && (op & ASN1_OP_END__OF)) { datalen = len; csp++; pc = machine[pc + 1]; pr_debug("- continue\n"); goto next_op; } if (dp != len) goto cons_length_error; len -= tdp; pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp); }
if (op & ASN1_OP_END__ACT) { unsigned char act; if (op & ASN1_OP_END__OF) act = machine[pc + 2]; else act = machine[pc + 1]; ret = actions[act](context, hdr, 0, data + tdp, len); if (ret < 0) return ret; } pc += asn1_op_lengths[op]; goto next_op;
case ASN1_OP_MAYBE_ACT: if (!(flags & FLAG_LAST_MATCHED)) { pc += asn1_op_lengths[op]; goto next_op; } fallthrough;
case ASN1_OP_ACT: ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len); if (ret < 0) return ret; pc += asn1_op_lengths[op]; goto next_op;
case ASN1_OP_RETURN: if (unlikely(jsp <= 0)) goto jump_stack_underflow; pc = jump_stack[--jsp]; flags |= FLAG_MATCHED | FLAG_LAST_MATCHED; goto next_op;
default: break; }
/* Shouldn't reach here */ pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n", op, pc); return -EBADMSG;
data_overrun_error: errmsg = "Data overrun error"; goto error;machine_overrun_error: errmsg = "Machine overrun error"; goto error;jump_stack_underflow: errmsg = "Jump stack underflow"; goto error;jump_stack_overflow: errmsg = "Jump stack overflow"; goto error;cons_stack_underflow: errmsg = "Cons stack underflow"; goto error;cons_stack_overflow: errmsg = "Cons stack overflow"; goto error;cons_length_error: errmsg = "Cons length error"; goto error;missing_eoc: errmsg = "Missing EOC in indefinite len cons"; goto error;invalid_eoc: errmsg = "Invalid length EOC"; goto error;length_too_long: errmsg = "Unsupported length"; goto error;indefinite_len_primitive: errmsg = "Indefinite len primitive not permitted"; goto error;tag_mismatch: errmsg = "Unexpected tag"; goto error;long_tag_not_supported: errmsg = "Long tag not supported";error: pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n", errmsg, pc, dp, optag, tag, len); return -EBADMSG;}EXPORT_SYMBOL_GPL(asn1_ber_decoder);
MODULE_DESCRIPTION("Decoder for ASN.1 BER/DER/CER encoded bytestream");MODULE_LICENSE("GPL");