/* b64dec.c - Simple Base64 decoder. * Copyright (C) 2008, 2011 Free Software Foundation, Inc. * Copyright (C) 2008, 2011, 2016 g10 Code GmbH * * This file is part of GnuPG. * * This file is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * This file is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this program; if not, see <https://www.gnu.org/licenses/>. */ #include <config.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <errno.h> #include <assert.h> #include "i18n.h" #include "util.h" /* The reverse base-64 list used for base-64 decoding. */ static unsigned char const asctobin[128] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0xff, 0xff, 0xff, 0xff, 0xff }; enum decoder_states { s_init, s_idle, s_lfseen, s_beginseen, s_waitheader, s_waitblank, s_begin, s_b64_0, s_b64_1, s_b64_2, s_b64_3, s_waitendtitle, s_waitend }; /* Initialize the context for the base64 decoder. If TITLE is NULL a plain base64 decoding is done. If it is the empty string the decoder will skip everything until a "-----BEGIN " line has been seen, decoding ends at a "----END " line. */ gpg_error_t b64dec_start (struct b64state *state, const char *title) { memset (state, 0, sizeof *state); if (title) { state->title = xtrystrdup (title); if (!state->title) state->lasterr = gpg_error_from_syserror (); else state->idx = s_init; } else state->idx = s_b64_0; return state->lasterr; } /* Do in-place decoding of base-64 data of LENGTH in BUFFER. Stores the new length of the buffer at R_NBYTES. */ gpg_error_t b64dec_proc (struct b64state *state, void *buffer, size_t length, size_t *r_nbytes) { enum decoder_states ds = state->idx; unsigned char val = state->radbuf[0]; int pos = state->quad_count; char *d, *s; if (state->lasterr) return state->lasterr; if (state->stop_seen) { *r_nbytes = 0; state->lasterr = gpg_error (GPG_ERR_EOF); xfree (state->title); state->title = NULL; return state->lasterr; } for (s=d=buffer; length && !state->stop_seen; length--, s++) { again: switch (ds) { case s_idle: if (*s == '\n') { ds = s_lfseen; pos = 0; } break; case s_init: ds = s_lfseen; /* fall through */ case s_lfseen: if (*s != "-----BEGIN "[pos]) { ds = s_idle; goto again; } else if (pos == 10) { pos = 0; ds = s_beginseen; } else pos++; break; case s_beginseen: if (*s != "PGP "[pos]) ds = s_begin; /* Not a PGP armor. */ else if (pos == 3) ds = s_waitheader; else pos++; break; case s_waitheader: if (*s == '\n') ds = s_waitblank; break; case s_waitblank: if (*s == '\n') ds = s_b64_0; /* blank line found. */ else if (*s == ' ' || *s == '\r' || *s == '\t') ; /* Ignore spaces. */ else { /* Armor header line. Note that we don't care that our * FSM accepts a header prefixed with spaces. */ ds = s_waitheader; /* Wait for next header. */ } break; case s_begin: if (*s == '\n') ds = s_b64_0; break; case s_b64_0: case s_b64_1: case s_b64_2: case s_b64_3: { int c; if (*s == '-' && state->title) { /* Not a valid Base64 character: assume end header. */ ds = s_waitend; } else if (*s == '=') { /* Pad character: stop */ if (ds == s_b64_1) *d++ = val; ds = state->title? s_waitendtitle : s_waitend; } else if (*s == '\n' || *s == ' ' || *s == '\r' || *s == '\t') ; /* Skip white spaces. */ else if ( (*s & 0x80) || (c = asctobin[*(unsigned char *)s]) == 255) { /* Skip invalid encodings. */ state->invalid_encoding = 1; } else if (ds == s_b64_0) { val = c << 2; ds = s_b64_1; } else if (ds == s_b64_1) { val |= (c>>4)&3; *d++ = val; val = (c<<4)&0xf0; ds = s_b64_2; } else if (ds == s_b64_2) { val |= (c>>2)&15; *d++ = val; val = (c<<6)&0xc0; ds = s_b64_3; } else { val |= c&0x3f; *d++ = val; ds = s_b64_0; } } break; case s_waitendtitle: if (*s == '-') ds = s_waitend; break; case s_waitend: if ( *s == '\n') state->stop_seen = 1; break; default: BUG(); } } state->idx = ds; state->radbuf[0] = val; state->quad_count = pos; *r_nbytes = (d -(char*) buffer); return 0; } /* This function needs to be called before releasing the decoder state. It may return an error code in case an encoding error has been found during decoding. */ gpg_error_t b64dec_finish (struct b64state *state) { xfree (state->title); state->title = NULL; if (state->lasterr) return state->lasterr; return state->invalid_encoding? gpg_error(GPG_ERR_BAD_DATA): 0; }