diff options
Diffstat (limited to 'src/b64dec.c')
| -rw-r--r-- | src/b64dec.c | 251 |
1 files changed, 251 insertions, 0 deletions
diff --git a/src/b64dec.c b/src/b64dec.c new file mode 100644 index 00000000..7965a305 --- /dev/null +++ b/src/b64dec.c @@ -0,0 +1,251 @@ +/* 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 <http://www.gnu.org/licenses/>. + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <assert.h> + +#include "gpgme.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 +_gpgme_b64dec_start (struct b64state *state, const char *title) +{ + memset (state, 0, sizeof *state); + if (title) + { + state->title = strdup (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 +_gpgme_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); + free (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; + 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: + assert (!"invalid state"); + } + } + + + 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 +_gpgme_b64dec_finish (struct b64state *state) +{ + if (state->lasterr) + return state->lasterr; + + free (state->title); + state->title = NULL; + return state->invalid_encoding? gpg_error(GPG_ERR_BAD_DATA): 0; +} |